feat: add terrain-core, tma, and unitdat crates with parsing functionality

- Introduced `terrain-core` crate for loading and processing terrain mesh data.
- Added `tma` crate for parsing mission files, including footer and object records.
- Created `unitdat` crate for reading unit data files with validation of structure.
- Implemented error handling and tests for all new crates.
- Documented object registry format and rendering pipeline in specifications.

2 files changed, 1805 insertions, 0 deletions

diff --git a/crates/render-mission-demo/src/lib.rs b/crates/render-mission-demo/src/lib.rs
new file mode 100644
index 0000000..9732f39
--- /dev/null
+++ b/crates/render-mission-demo/src/lib.rs
@@ -0,0 +1,881 @@
+use encoding_rs::WINDOWS_1251;
+use nres::Archive;
+use render_core::{build_render_mesh, RenderMesh};
+use render_demo::{load_model_with_name_from_archive, resolve_texture_for_model, LoadedTexture};
+use std::collections::HashMap;
+use std::fmt;
+use std::fs;
+use std::path::{Path, PathBuf};
+use terrain_core::TerrainMesh;
+use tma::MissionFile;
+
+const MAT0_KIND: u32 = 0x3054_414D;
+const MESH_KIND: u32 = 0x4853_454D;
+const OBJECT_REF_STRIDE: usize = 64;
+const OBJECT_REF_ARCHIVE_BYTES: usize = 32;
+
+pub type Result<T> = core::result::Result<T, Error>;
+
+#[derive(Debug)]
+pub enum Error {
+    Io(std::io::Error),
+    Mission(tma::Error),
+    Terrain(terrain_core::Error),
+    UnitDat(unitdat::Error),
+    RenderDemo(render_demo::Error),
+    Nres(nres::error::Error),
+    Texm(texm::error::Error),
+    InvalidMapPath(String),
+    GameRootNotFound(PathBuf),
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Io(err) => write!(f, "{err}"),
+            Self::Mission(err) => write!(f, "{err}"),
+            Self::Terrain(err) => write!(f, "{err}"),
+            Self::UnitDat(err) => write!(f, "{err}"),
+            Self::RenderDemo(err) => write!(f, "{err}"),
+            Self::Nres(err) => write!(f, "{err}"),
+            Self::Texm(err) => write!(f, "{err}"),
+            Self::InvalidMapPath(path) => write!(f, "invalid mission map path: {path}"),
+            Self::GameRootNotFound(path) => {
+                write!(
+                    f,
+                    "failed to detect game root from mission path {}",
+                    path.display()
+                )
+            }
+        }
+    }
+}
+
+impl std::error::Error for Error {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        match self {
+            Self::Io(err) => Some(err),
+            Self::Mission(err) => Some(err),
+            Self::Terrain(err) => Some(err),
+            Self::UnitDat(err) => Some(err),
+            Self::RenderDemo(err) => Some(err),
+            Self::Nres(err) => Some(err),
+            Self::Texm(err) => Some(err),
+            Self::InvalidMapPath(_) | Self::GameRootNotFound(_) => None,
+        }
+    }
+}
+
+impl From<std::io::Error> for Error {
+    fn from(value: std::io::Error) -> Self {
+        Self::Io(value)
+    }
+}
+
+impl From<tma::Error> for Error {
+    fn from(value: tma::Error) -> Self {
+        Self::Mission(value)
+    }
+}
+
+impl From<terrain_core::Error> for Error {
+    fn from(value: terrain_core::Error) -> Self {
+        Self::Terrain(value)
+    }
+}
+
+impl From<unitdat::Error> for Error {
+    fn from(value: unitdat::Error) -> Self {
+        Self::UnitDat(value)
+    }
+}
+
+impl From<render_demo::Error> for Error {
+    fn from(value: render_demo::Error) -> Self {
+        Self::RenderDemo(value)
+    }
+}
+
+impl From<nres::error::Error> for Error {
+    fn from(value: nres::error::Error) -> Self {
+        Self::Nres(value)
+    }
+}
+
+impl From<texm::error::Error> for Error {
+    fn from(value: texm::error::Error) -> Self {
+        Self::Texm(value)
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+pub struct LoadOptions {
+    pub load_model_textures: bool,
+    pub load_terrain_texture: bool,
+}
+
+impl Default for LoadOptions {
+    fn default() -> Self {
+        Self {
+            load_model_textures: true,
+            load_terrain_texture: true,
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct MissionScene {
+    pub game_root: PathBuf,
+    pub mission_path: PathBuf,
+    pub mission: MissionFile,
+    pub map_folder_rel: PathBuf,
+    pub land_msh_path: PathBuf,
+    pub terrain: TerrainMesh,
+    pub terrain_texture: Option<LoadedTexture>,
+    pub models: Vec<SceneModel>,
+    pub skipped_objects: usize,
+}
+
+#[derive(Clone, Debug)]
+pub struct SceneModel {
+    pub archive_path: PathBuf,
+    pub model_name: String,
+    pub mesh: RenderMesh,
+    pub texture: Option<LoadedTexture>,
+    pub instances: Vec<ModelInstance>,
+}
+
+#[derive(Copy, Clone, Debug)]
+pub struct ModelInstance {
+    pub position: [f32; 3],
+    pub yaw_rad: f32,
+    pub scale: [f32; 3],
+}
+
+#[derive(Clone, Debug)]
+struct ObjectPrototype {
+    archive_path: PathBuf,
+    model_name: String,
+}
+
+#[derive(Clone, Debug)]
+struct ObjectRef {
+    archive_name: String,
+    resource_name: String,
+}
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+struct ModelKey {
+    archive_path: PathBuf,
+    model_name: String,
+}
+
+pub fn detect_game_root_from_mission_path(mission_path: &Path) -> Option<PathBuf> {
+    let mut cursor = mission_path.parent();
+    while let Some(dir) = cursor {
+        if dir.join("DATA").is_dir() && dir.join("objects.rlb").is_file() {
+            return Some(dir.to_path_buf());
+        }
+        cursor = dir.parent();
+    }
+    None
+}
+
+pub fn load_scene(
+    game_root: impl AsRef<Path>,
+    mission_path: impl AsRef<Path>,
+) -> Result<MissionScene> {
+    load_scene_with_options(game_root, mission_path, LoadOptions::default())
+}
+
+pub fn load_scene_with_options(
+    game_root: impl AsRef<Path>,
+    mission_path: impl AsRef<Path>,
+    options: LoadOptions,
+) -> Result<MissionScene> {
+    let game_root = game_root.as_ref().to_path_buf();
+    let mission_path = mission_path.as_ref().to_path_buf();
+
+    let mission = tma::parse_path(&mission_path)?;
+    let map_folder_rel = map_folder_from_footer(&mission.footer.map_path)?;
+    let land_msh_path = game_root.join(&map_folder_rel).join("Land.msh");
+    let terrain = terrain_core::load_land_mesh(&land_msh_path)?;
+    let terrain_texture = if options.load_terrain_texture {
+        resolve_terrain_texture(&game_root, &map_folder_rel)?
+    } else {
+        None
+    };
+
+    let mut grouped_instances: HashMap<ModelKey, Vec<ModelInstance>> = HashMap::new();
+    let mut prototype_cache: HashMap<String, Option<ObjectPrototype>> = HashMap::new();
+    let mut skipped = 0usize;
+
+    for object in &mission.objects {
+        let cache_key = object.resource_name.to_ascii_lowercase();
+        let proto = if let Some(cached) = prototype_cache.get(&cache_key) {
+            cached.clone()
+        } else {
+            let resolved = resolve_object_prototype(&game_root, object)?;
+            prototype_cache.insert(cache_key, resolved.clone());
+            resolved
+        };
+
+        let Some(proto) = proto else {
+            skipped += 1;
+            continue;
+        };
+
+        let instance = ModelInstance {
+            position: object.position,
+            yaw_rad: object.orientation[2],
+            scale: normalize_scale(object.scale),
+        };
+
+        grouped_instances
+            .entry(ModelKey {
+                archive_path: proto.archive_path,
+                model_name: proto.model_name,
+            })
+            .or_default()
+            .push(instance);
+    }
+
+    let mut models = Vec::new();
+    for (key, instances) in grouped_instances {
+        let loaded =
+            match load_model_with_name_from_archive(&key.archive_path, Some(&key.model_name)) {
+                Ok(v) => v,
+                Err(_) => {
+                    skipped += instances.len();
+                    continue;
+                }
+            };
+
+        let mesh = build_render_mesh(&loaded.model, 0, 0);
+        if mesh.indices.is_empty() {
+            skipped += instances.len();
+            continue;
+        }
+
+        let texture = if options.load_model_textures {
+            resolve_texture_for_model(&key.archive_path, &loaded.name, None, None, None, None)
+                .ok()
+                .flatten()
+        } else {
+            None
+        };
+
+        models.push(SceneModel {
+            archive_path: key.archive_path,
+            model_name: loaded.name,
+            mesh,
+            texture,
+            instances,
+        });
+    }
+
+    models.sort_by(|a, b| a.model_name.cmp(&b.model_name));
+
+    Ok(MissionScene {
+        game_root,
+        mission_path,
+        mission,
+        map_folder_rel,
+        land_msh_path,
+        terrain,
+        terrain_texture,
+        models,
+        skipped_objects: skipped,
+    })
+}
+
+pub fn compute_scene_bounds(scene: &MissionScene) -> Option<([f32; 3], [f32; 3])> {
+    let mut min_v = [f32::INFINITY; 3];
+    let mut max_v = [f32::NEG_INFINITY; 3];
+    let mut any = false;
+
+    for pos in &scene.terrain.positions {
+        merge_bounds(&mut min_v, &mut max_v, *pos);
+        any = true;
+    }
+
+    for model in &scene.models {
+        for instance in &model.instances {
+            merge_bounds(&mut min_v, &mut max_v, instance.position);
+            any = true;
+        }
+    }
+
+    any.then_some((min_v, max_v))
+}
+
+fn merge_bounds(min_v: &mut [f32; 3], max_v: &mut [f32; 3], p: [f32; 3]) {
+    for i in 0..3 {
+        if p[i] < min_v[i] {
+            min_v[i] = p[i];
+        }
+        if p[i] > max_v[i] {
+            max_v[i] = p[i];
+        }
+    }
+}
+
+fn normalize_scale(scale: [f32; 3]) -> [f32; 3] {
+    let mut out = scale;
+    for item in &mut out {
+        if !item.is_finite() || item.abs() < 0.000_1 {
+            *item = 1.0;
+        }
+    }
+    out
+}
+
+fn map_folder_from_footer(map_path: &str) -> Result<PathBuf> {
+    let mut parts = split_relative_path(map_path);
+    if parts.len() < 2 {
+        return Err(Error::InvalidMapPath(map_path.to_string()));
+    }
+    parts.pop(); // remove 'land'
+
+    let mut out = PathBuf::new();
+    for part in parts {
+        out.push(part);
+    }
+    Ok(out)
+}
+
+fn resolve_object_prototype(
+    game_root: &Path,
+    object: &tma::MissionObject,
+) -> Result<Option<ObjectPrototype>> {
+    if object.resource_name.to_ascii_lowercase().ends_with(".dat") {
+        let dat_path = game_root.join(pathbuf_from_rel(&object.resource_name));
+        if !dat_path.is_file() {
+            return Ok(None);
+        }
+
+        let parsed = unitdat::parse_path(&dat_path)?;
+        let archive_path = game_root.join(pathbuf_from_rel(&parsed.archive_name));
+        if !archive_path.is_file() {
+            return Ok(None);
+        }
+        return resolve_archive_model(game_root, &archive_path, &parsed.model_key);
+    }
+
+    let archive_path = game_root.join("objects.rlb");
+    if !archive_path.is_file() {
+        return Ok(None);
+    }
+    resolve_archive_model(game_root, &archive_path, &object.resource_name)
+}
+
+fn resolve_archive_model(
+    game_root: &Path,
+    archive_path: &Path,
+    model_key: &str,
+) -> Result<Option<ObjectPrototype>> {
+    if !archive_path.is_file() {
+        return Ok(None);
+    }
+
+    if is_objects_registry_archive(archive_path) {
+        if let Some(proto) = resolve_objects_registry_model(game_root, archive_path, model_key)? {
+            return Ok(Some(proto));
+        }
+    }
+
+    let model_name = ensure_msh_suffix(model_key);
+    if !archive_has_mesh_entry(archive_path, &model_name)? {
+        return Ok(None);
+    }
+
+    Ok(Some(ObjectPrototype {
+        archive_path: archive_path.to_path_buf(),
+        model_name: model_name.to_ascii_lowercase(),
+    }))
+}
+
+fn is_objects_registry_archive(archive_path: &Path) -> bool {
+    archive_path
+        .file_name()
+        .and_then(|name| name.to_str())
+        .is_some_and(|name| name.eq_ignore_ascii_case("objects.rlb"))
+}
+
+fn resolve_objects_registry_model(
+    game_root: &Path,
+    registry_archive_path: &Path,
+    object_key: &str,
+) -> Result<Option<ObjectPrototype>> {
+    let archive = Archive::open_path(registry_archive_path)?;
+    let Some(entry_id) = find_registry_entry_id(&archive, object_key) else {
+        return Ok(None);
+    };
+
+    let payload = archive.read(entry_id)?.into_owned();
+    let refs = parse_object_refs(&payload);
+    if refs.is_empty() {
+        return Ok(None);
+    }
+
+    for item in refs
+        .iter()
+        .filter(|item| has_extension(&item.resource_name, "msh"))
+    {
+        if let Some(proto) = resolve_object_ref_model(game_root, item, &item.resource_name)? {
+            return Ok(Some(proto));
+        }
+    }
+
+    for item in refs
+        .iter()
+        .filter(|item| has_extension(&item.resource_name, "bas"))
+    {
+        let Some(stem) = Path::new(&item.resource_name)
+            .file_stem()
+            .and_then(|stem| stem.to_str())
+        else {
+            continue;
+        };
+        if stem.is_empty() {
+            continue;
+        }
+        let candidate = format!("{stem}.msh");
+        if let Some(proto) = resolve_object_ref_model(game_root, item, &candidate)? {
+            return Ok(Some(proto));
+        }
+    }
+
+    Ok(None)
+}
+
+fn find_registry_entry_id(archive: &Archive, object_key: &str) -> Option<nres::EntryId> {
+    mesh_name_candidates(object_key)
+        .into_iter()
+        .find_map(|candidate| archive.find(&candidate))
+}
+
+fn resolve_object_ref_model(
+    game_root: &Path,
+    item: &ObjectRef,
+    model_name: &str,
+) -> Result<Option<ObjectPrototype>> {
+    let archive_path = game_root.join(pathbuf_from_rel(&item.archive_name));
+    if !archive_path.is_file() {
+        return Ok(None);
+    }
+    if !archive_has_mesh_entry(&archive_path, model_name)? {
+        return Ok(None);
+    }
+
+    Ok(Some(ObjectPrototype {
+        archive_path,
+        model_name: model_name.to_ascii_lowercase(),
+    }))
+}
+
+fn parse_object_refs(payload: &[u8]) -> Vec<ObjectRef> {
+    if !payload.len().is_multiple_of(OBJECT_REF_STRIDE) {
+        return Vec::new();
+    }
+
+    let mut refs = Vec::with_capacity(payload.len() / OBJECT_REF_STRIDE);
+    for chunk in payload.chunks_exact(OBJECT_REF_STRIDE) {
+        let archive_name = decode_cp1251_cstr(&chunk[..OBJECT_REF_ARCHIVE_BYTES]);
+        let resource_name = decode_cp1251_cstr(&chunk[OBJECT_REF_ARCHIVE_BYTES..]);
+        if archive_name.is_empty() || resource_name.is_empty() {
+            continue;
+        }
+        refs.push(ObjectRef {
+            archive_name,
+            resource_name,
+        });
+    }
+    refs
+}
+
+fn archive_has_mesh_entry(archive_path: &Path, requested_name: &str) -> Result<bool> {
+    let archive = Archive::open_path(archive_path)?;
+    Ok(find_mesh_entry_id(&archive, requested_name).is_some())
+}
+
+fn find_mesh_entry_id(archive: &Archive, requested_name: &str) -> Option<nres::EntryId> {
+    for candidate in mesh_name_candidates(requested_name) {
+        let Some(id) = archive.find(&candidate) else {
+            continue;
+        };
+        let Some(entry) = archive.get(id) else {
+            continue;
+        };
+        if entry.meta.kind == MESH_KIND || has_extension(&entry.meta.name, "msh") {
+            return Some(id);
+        }
+    }
+    None
+}
+
+fn mesh_name_candidates(name: &str) -> Vec<String> {
+    let mut out = Vec::new();
+    let trimmed = name.trim();
+    if trimmed.is_empty() {
+        return out;
+    }
+
+    push_unique_string(&mut out, trimmed.to_string());
+    if let Some(stem) = trimmed
+        .strip_suffix(".msh")
+        .or_else(|| trimmed.strip_suffix(".MSH"))
+    {
+        if !stem.is_empty() {
+            push_unique_string(&mut out, stem.to_string());
+        }
+    } else {
+        push_unique_string(&mut out, format!("{trimmed}.msh"));
+    }
+
+    out
+}
+
+fn push_unique_string(items: &mut Vec<String>, value: String) {
+    if !items.iter().any(|item| item.eq_ignore_ascii_case(&value)) {
+        items.push(value);
+    }
+}
+
+fn ensure_msh_suffix(name: &str) -> String {
+    let trimmed = name.trim();
+    if trimmed.to_ascii_lowercase().ends_with(".msh") {
+        trimmed.to_string()
+    } else {
+        format!("{trimmed}.msh")
+    }
+}
+
+fn has_extension(name: &str, ext: &str) -> bool {
+    Path::new(name)
+        .extension()
+        .and_then(|value| value.to_str())
+        .is_some_and(|value| value.eq_ignore_ascii_case(ext))
+}
+
+fn resolve_terrain_texture(
+    game_root: &Path,
+    map_folder_rel: &Path,
+) -> Result<Option<LoadedTexture>> {
+    let material_archive_path = game_root.join("material.lib");
+    let texture_archive_path = game_root.join("textures.lib");
+    if !material_archive_path.is_file() || !texture_archive_path.is_file() {
+        return Ok(None);
+    }
+
+    for wear_name in ["Land1.wea", "Land2.wea"] {
+        let wear_path = game_root.join(map_folder_rel).join(wear_name);
+        if !wear_path.is_file() {
+            continue;
+        }
+        let wear_payload = fs::read(&wear_path)?;
+        let Some(material_name) = parse_primary_material_from_wear(&wear_payload) else {
+            continue;
+        };
+        let Some(texture_name) =
+            resolve_texture_name_from_material_archive(&material_archive_path, &material_name)?
+        else {
+            continue;
+        };
+        if let Some(texture) = load_texm_by_name(&texture_archive_path, &texture_name)? {
+            return Ok(Some(texture));
+        }
+    }
+
+    Ok(None)
+}
+
+fn parse_primary_material_from_wear(bytes: &[u8]) -> Option<String> {
+    let text = decode_cp1251(bytes).replace('\r', "");
+    let mut lines = text.lines();
+    let count = lines.next()?.trim().parse::<usize>().ok()?;
+    if count == 0 {
+        return None;
+    }
+
+    for line in lines.take(count) {
+        let mut parts = line.split_whitespace();
+        let _legacy = parts.next()?;
+        let name = parts.next()?;
+        if !name.is_empty() {
+            return Some(name.to_string());
+        }
+    }
+    None
+}
+
+fn resolve_texture_name_from_material_archive(
+    archive_path: &Path,
+    material_name: &str,
+) -> Result<Option<String>> {
+    let archive = Archive::open_path(archive_path)?;
+
+    let entry = if let Some(id) = archive.find(material_name) {
+        archive
+            .get(id)
+            .filter(|entry| entry.meta.kind == MAT0_KIND)
+            .or_else(|| {
+                archive
+                    .find("DEFAULT")
+                    .and_then(|id| archive.get(id))
+                    .filter(|entry| entry.meta.kind == MAT0_KIND)
+            })
+    } else {
+        archive
+            .find("DEFAULT")
+            .and_then(|id| archive.get(id))
+            .filter(|entry| entry.meta.kind == MAT0_KIND)
+    }
+    .or_else(|| archive.entries().find(|entry| entry.meta.kind == MAT0_KIND));
+
+    let Some(entry) = entry else {
+        return Ok(None);
+    };
+
+    let payload = archive.read(entry.id)?.into_owned();
+    parse_primary_texture_name_from_mat0(&payload, entry.meta.attr2)
+}
+
+fn parse_primary_texture_name_from_mat0(payload: &[u8], attr2: u32) -> Result<Option<String>> {
+    if payload.len() < 4 {
+        return Ok(None);
+    }
+
+    let phase_count = u16::from_le_bytes([payload[0], payload[1]]) as usize;
+    if phase_count == 0 {
+        return Ok(None);
+    }
+
+    let mut offset = 4usize;
+    if attr2 >= 2 {
+        offset = offset.saturating_add(2);
+    }
+    if attr2 >= 3 {
+        offset = offset.saturating_add(4);
+    }
+    if attr2 >= 4 {
+        offset = offset.saturating_add(4);
+    }
+
+    for phase in 0..phase_count {
+        let phase_off = offset.saturating_add(phase.saturating_mul(34));
+        let Some(rec) = payload.get(phase_off..phase_off + 34) else {
+            break;
+        };
+        let name_raw = &rec[18..34];
+        let end = name_raw
+            .iter()
+            .position(|&b| b == 0)
+            .unwrap_or(name_raw.len());
+        let name = decode_cp1251(&name_raw[..end]).trim().to_string();
+        if !name.is_empty() {
+            return Ok(Some(name));
+        }
+    }
+
+    Ok(None)
+}
+
+fn load_texm_by_name(archive_path: &Path, texture_name: &str) -> Result<Option<LoadedTexture>> {
+    let archive = Archive::open_path(archive_path)?;
+    let Some(id) = archive.find(texture_name) else {
+        return Ok(None);
+    };
+    let Some(entry) = archive.get(id) else {
+        return Ok(None);
+    };
+    if entry.meta.kind != texm::TEXM_MAGIC {
+        return Ok(None);
+    }
+
+    let payload = archive.read(id)?.into_owned();
+    let parsed = texm::parse_texm(&payload)?;
+    let decoded = texm::decode_mip_rgba8(&parsed, &payload, 0)?;
+
+    Ok(Some(LoadedTexture {
+        name: entry.meta.name.clone(),
+        width: decoded.width,
+        height: decoded.height,
+        rgba8: decoded.rgba8,
+    }))
+}
+
+fn split_relative_path(path: &str) -> Vec<&str> {
+    path.split(['\\', '/'])
+        .filter(|part| !part.is_empty())
+        .collect()
+}
+
+fn pathbuf_from_rel(path: &str) -> PathBuf {
+    let mut out = PathBuf::new();
+    for part in split_relative_path(path) {
+        out.push(part);
+    }
+    out
+}
+
+fn decode_cp1251_cstr(bytes: &[u8]) -> String {
+    let end = bytes.iter().position(|&b| b == 0).unwrap_or(bytes.len());
+    let (decoded, _, _) = WINDOWS_1251.decode(&bytes[..end]);
+    decoded.trim().to_string()
+}
+
+fn decode_cp1251(bytes: &[u8]) -> String {
+    let (decoded, _, _) = WINDOWS_1251.decode(bytes);
+    decoded.into_owned()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::path::Path;
+
+    fn game_root() -> Option<PathBuf> {
+        let root = Path::new(env!("CARGO_MANIFEST_DIR"))
+            .join("..")
+            .join("..")
+            .join("testdata")
+            .join("Parkan - Iron Strategy");
+        root.is_dir().then_some(root)
+    }
+
+    #[test]
+    fn detects_game_root_from_mission_path() {
+        let Some(root) = game_root() else {
+            eprintln!("skipping: game root missing");
+            return;
+        };
+
+        let mission = root
+            .join("MISSIONS")
+            .join("CAMPAIGN")
+            .join("CAMPAIGN.00")
+            .join("Mission.01")
+            .join("data.tma");
+        if !mission.is_file() {
+            eprintln!("skipping missing mission sample");
+            return;
+        }
+
+        let detected = detect_game_root_from_mission_path(&mission)
+            .expect("failed to detect game root from mission path");
+        assert_eq!(detected, root);
+    }
+
+    #[test]
+    fn loads_scene_cpu_without_textures() {
+        let Some(root) = game_root() else {
+            eprintln!("skipping: game root missing");
+            return;
+        };
+
+        let mission = root
+            .join("MISSIONS")
+            .join("CAMPAIGN")
+            .join("CAMPAIGN.00")
+            .join("Mission.01")
+            .join("data.tma");
+        if !mission.is_file() {
+            eprintln!("skipping missing mission sample");
+            return;
+        }
+
+        let scene = load_scene_with_options(
+            &root,
+            &mission,
+            LoadOptions {
+                load_model_textures: false,
+                load_terrain_texture: false,
+            },
+        )
+        .unwrap_or_else(|err| panic!("failed to load scene {}: {err}", mission.display()));
+
+        assert!(!scene.terrain.positions.is_empty());
+        assert!(!scene.terrain.faces.is_empty());
+        assert!(!scene.models.is_empty());
+
+        let instance_count = scene
+            .models
+            .iter()
+            .map(|model| model.instances.len())
+            .sum::<usize>();
+        assert!(instance_count >= 10);
+
+        let bounds = compute_scene_bounds(&scene).expect("scene bounds should exist");
+        assert!(bounds.0[0] <= bounds.1[0]);
+        assert!(bounds.0[1] <= bounds.1[1]);
+        assert!(bounds.0[2] <= bounds.1[2]);
+    }
+
+    #[test]
+    fn loads_scene_with_textures() {
+        let Some(root) = game_root() else {
+            eprintln!("skipping: game root missing");
+            return;
+        };
+
+        let mission = root
+            .join("MISSIONS")
+            .join("CAMPAIGN")
+            .join("CAMPAIGN.00")
+            .join("Mission.01")
+            .join("data.tma");
+        if !mission.is_file() {
+            eprintln!("skipping missing mission sample");
+            return;
+        }
+
+        let scene = load_scene_with_options(&root, &mission, LoadOptions::default())
+            .unwrap_or_else(|err| panic!("failed to load textured scene {}: {err}", mission.display()));
+
+        assert!(!scene.models.is_empty());
+        let textured_models = scene.models.iter().filter(|model| model.texture.is_some()).count();
+        assert!(textured_models > 0, "no model textures resolved");
+        assert!(scene.terrain_texture.is_some(), "terrain texture was not resolved");
+    }
+
+    #[test]
+    fn resolves_objects_registry_models() {
+        let Some(root) = game_root() else {
+            eprintln!("skipping: game root missing");
+            return;
+        };
+
+        let registry = root.join("objects.rlb");
+        if !registry.is_file() {
+            eprintln!("skipping missing objects.rlb");
+            return;
+        }
+
+        let cases = [
+            ("r_h_01", "bases.rlb", "r_h_01.msh"),
+            ("s_tree_04", "static.rlb", "s_tree_0_04.msh"),
+            ("fr_m_brige", "fortif.rlb", "fr_m_brige.msh"),
+        ];
+
+        for (key, archive_name, model_name) in cases {
+            let proto = resolve_objects_registry_model(&root, &registry, key)
+                .unwrap_or_else(|err| panic!("failed to resolve '{key}' from objects.rlb: {err}"))
+                .unwrap_or_else(|| panic!("missing model resolution for '{key}'"));
+
+            let got_archive = proto
+                .archive_path
+                .file_name()
+                .and_then(|name| name.to_str())
+                .map(|name| name.to_ascii_lowercase())
+                .unwrap_or_default();
+            assert_eq!(got_archive, archive_name.to_ascii_lowercase());
+            assert!(
+                proto.model_name.eq_ignore_ascii_case(model_name),
+                "unexpected model for key '{key}': got '{}', expected '{}'",
+                proto.model_name,
+                model_name
+            );
+        }
+    }
+}
diff --git a/crates/render-mission-demo/src/main.rs b/crates/render-mission-demo/src/main.rs
new file mode 100644
index 0000000..01b6e06
--- /dev/null
+++ b/crates/render-mission-demo/src/main.rs
@@ -0,0 +1,924 @@
+use glow::HasContext as _;
+use render_mission_demo::{
+    compute_scene_bounds, detect_game_root_from_mission_path, load_scene_with_options, LoadOptions,
+    MissionScene, ModelInstance,
+};
+use std::io::Write as _;
+use std::path::PathBuf;
+use std::time::{Duration, Instant};
+
+struct Args {
+    mission: PathBuf,
+    game_root: Option<PathBuf>,
+    width: u32,
+    height: u32,
+    fov_deg: f32,
+    no_model_texture: bool,
+    no_terrain_texture: bool,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+enum GlBackend {
+    Gles2,
+    Core33,
+}
+
+struct GpuTexture {
+    handle: glow::NativeTexture,
+}
+
+struct GpuRenderable {
+    vbo: glow::NativeBuffer,
+    ebo: glow::NativeBuffer,
+    index_count: usize,
+    texture: Option<GpuTexture>,
+}
+
+struct ModelRenderable {
+    gpu: GpuRenderable,
+    instances: Vec<ModelInstance>,
+}
+
+#[derive(Copy, Clone, Debug)]
+struct Camera {
+    position: [f32; 3],
+    yaw: f32,
+    pitch: f32,
+    move_speed: f32,
+    mouse_sensitivity: f32,
+}
+
+fn parse_args() -> Result<Args, String> {
+    let mut mission = None;
+    let mut game_root = None;
+    let mut width = 1600u32;
+    let mut height = 900u32;
+    let mut fov_deg = 60.0f32;
+    let mut no_model_texture = false;
+    let mut no_terrain_texture = false;
+
+    let mut it = std::env::args().skip(1);
+    while let Some(arg) = it.next() {
+        match arg.as_str() {
+            "--mission" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --mission"))?;
+                mission = Some(PathBuf::from(value));
+            }
+            "--game-root" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --game-root"))?;
+                game_root = Some(PathBuf::from(value));
+            }
+            "--width" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --width"))?;
+                width = value
+                    .parse::<u32>()
+                    .map_err(|_| String::from("invalid --width value"))?;
+                if width == 0 {
+                    return Err(String::from("--width must be > 0"));
+                }
+            }
+            "--height" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --height"))?;
+                height = value
+                    .parse::<u32>()
+                    .map_err(|_| String::from("invalid --height value"))?;
+                if height == 0 {
+                    return Err(String::from("--height must be > 0"));
+                }
+            }
+            "--fov" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --fov"))?;
+                fov_deg = value
+                    .parse::<f32>()
+                    .map_err(|_| String::from("invalid --fov value"))?;
+                if !(1.0..=179.0).contains(&fov_deg) {
+                    return Err(String::from("--fov must be in range [1, 179]"));
+                }
+            }
+            "--no-model-texture" => {
+                no_model_texture = true;
+            }
+            "--no-terrain-texture" => {
+                no_terrain_texture = true;
+            }
+            "--help" | "-h" => {
+                print_help();
+                std::process::exit(0);
+            }
+            other => {
+                return Err(format!("unknown argument: {other}"));
+            }
+        }
+    }
+
+    let mission = mission.ok_or_else(|| String::from("missing required --mission"))?;
+    Ok(Args {
+        mission,
+        game_root,
+        width,
+        height,
+        fov_deg,
+        no_model_texture,
+        no_terrain_texture,
+    })
+}
+
+fn print_help() {
+    eprintln!("parkan-render-mission-demo --mission <path/to/data.tma> [--game-root <path>] [--width W] [--height H] [--fov DEG]");
+    eprintln!("                          [--no-model-texture] [--no-terrain-texture]");
+    eprintln!("controls: arrows/WASD move, PageUp/PageDown vertical move, Right Mouse drag look, Shift speed-up, Esc exit");
+}
+
+fn main() {
+    let args = match parse_args() {
+        Ok(v) => v,
+        Err(err) => {
+            eprintln!("{err}");
+            print_help();
+            std::process::exit(2);
+        }
+    };
+
+    if let Err(err) = run(args) {
+        eprintln!("{err}");
+        std::process::exit(1);
+    }
+}
+
+fn run(args: Args) -> Result<(), String> {
+    let game_root = if let Some(path) = args.game_root.clone() {
+        path
+    } else {
+        detect_game_root_from_mission_path(&args.mission).ok_or_else(|| {
+            format!(
+                "failed to detect game root from mission path {} (use --game-root)",
+                args.mission.display()
+            )
+        })?
+    };
+
+    let scene = load_scene_with_options(
+        &game_root,
+        &args.mission,
+        LoadOptions {
+            load_model_textures: !args.no_model_texture,
+            load_terrain_texture: !args.no_terrain_texture,
+        },
+    )
+    .map_err(|err| format!("failed to load mission scene: {err}"))?;
+
+    let terrain_mesh = terrain_core::build_render_mesh(&scene.terrain)
+        .map_err(|err| format!("failed to build terrain render mesh: {err}"))?;
+
+    let instance_count = scene
+        .models
+        .iter()
+        .map(|model| model.instances.len())
+        .sum::<usize>();
+    println!(
+        "mission loaded: map='{}', terrain_vertices={}, terrain_faces={}, models={}, instances={}, skipped={}",
+        scene.mission.footer.map_path,
+        scene.terrain.positions.len(),
+        scene.terrain.faces.len(),
+        scene.models.len(),
+        instance_count,
+        scene.skipped_objects
+    );
+
+    let sdl = sdl2::init().map_err(|err| format!("failed to init SDL2: {err}"))?;
+    let video = sdl
+        .video()
+        .map_err(|err| format!("failed to init SDL2 video: {err}"))?;
+
+    let (mut window, _gl_ctx, gl_backend) =
+        create_window_and_context(&video, args.width, args.height)?;
+    let _ = video.gl_set_swap_interval(1);
+
+    let gl = unsafe {
+        glow::Context::from_loader_function(|name| video.gl_get_proc_address(name) as *const _)
+    };
+
+    let program = unsafe { create_program(&gl, gl_backend)? };
+    let u_mvp = unsafe { gl.get_uniform_location(program, "u_mvp") };
+    let u_use_tex = unsafe { gl.get_uniform_location(program, "u_use_tex") };
+    let u_tex = unsafe { gl.get_uniform_location(program, "u_tex") };
+    let a_pos = unsafe { gl.get_attrib_location(program, "a_pos") }
+        .ok_or_else(|| String::from("shader attribute a_pos is missing"))?;
+    let a_uv = unsafe { gl.get_attrib_location(program, "a_uv") }
+        .ok_or_else(|| String::from("shader attribute a_uv is missing"))?;
+
+    let terrain_gpu =
+        unsafe { upload_terrain_renderable(&gl, &terrain_mesh, scene.terrain_texture.as_ref())? };
+
+    let mut model_gpus = Vec::new();
+    for model in &scene.models {
+        let renderable = unsafe { upload_model_renderable(&gl, model)? };
+        model_gpus.push(renderable);
+    }
+
+    let (scene_center, scene_radius) = initial_scene_sphere(&scene);
+    let mut camera = Camera {
+        position: [
+            scene_center[0],
+            scene_center[1] + scene_radius * 0.6,
+            scene_center[2] + scene_radius * 1.4,
+        ],
+        yaw: std::f32::consts::PI,
+        pitch: -0.28,
+        move_speed: (scene_radius * 0.55).max(60.0),
+        mouse_sensitivity: 0.005,
+    };
+
+    let mut events = sdl
+        .event_pump()
+        .map_err(|err| format!("failed to get SDL event pump: {err}"))?;
+    let mut last = Instant::now();
+    let mut fps_window_start = Instant::now();
+    let mut fps_frames = 0u32;
+    let mut fps_printed = false;
+    let mut mouse_look = false;
+
+    'main_loop: loop {
+        for event in events.poll_iter() {
+            match event {
+                sdl2::event::Event::Quit { .. } => break 'main_loop,
+                sdl2::event::Event::KeyDown {
+                    keycode: Some(sdl2::keyboard::Keycode::Escape),
+                    ..
+                } => break 'main_loop,
+                sdl2::event::Event::MouseButtonDown {
+                    mouse_btn: sdl2::mouse::MouseButton::Right,
+                    ..
+                } => {
+                    mouse_look = true;
+                    sdl.mouse().set_relative_mouse_mode(true);
+                }
+                sdl2::event::Event::MouseButtonUp {
+                    mouse_btn: sdl2::mouse::MouseButton::Right,
+                    ..
+                } => {
+                    mouse_look = false;
+                    sdl.mouse().set_relative_mouse_mode(false);
+                }
+                sdl2::event::Event::MouseMotion { xrel, yrel, .. } if mouse_look => {
+                    camera.yaw += xrel as f32 * camera.mouse_sensitivity;
+                    camera.pitch -= yrel as f32 * camera.mouse_sensitivity;
+                    camera.pitch = camera.pitch.clamp(-1.54, 1.54);
+                }
+                _ => {}
+            }
+        }
+
+        let now = Instant::now();
+        let dt = (now - last).as_secs_f32().clamp(0.0, 0.05);
+        last = now;
+
+        update_camera(&events, &mut camera, dt);
+
+        let (w, h) = window.size();
+        let proj = mat4_perspective(
+            args.fov_deg.to_radians(),
+            (w as f32 / h.max(1) as f32).max(0.01),
+            0.1,
+            (scene_radius * 25.0).max(5000.0),
+        );
+        let forward = camera_forward(camera.yaw, camera.pitch);
+        let view = mat4_look_at(
+            camera.position,
+            [
+                camera.position[0] + forward[0],
+                camera.position[1] + forward[1],
+                camera.position[2] + forward[2],
+            ],
+            [0.0, 1.0, 0.0],
+        );
+
+        unsafe {
+            draw_frame_begin(&gl, w, h);
+
+            let terrain_mvp = mat4_mul(&proj, &view);
+            draw_gpu_renderable(
+                &gl,
+                program,
+                u_mvp.as_ref(),
+                u_use_tex.as_ref(),
+                u_tex.as_ref(),
+                a_pos,
+                a_uv,
+                &terrain_gpu,
+                &terrain_mvp,
+            );
+
+            for model in &model_gpus {
+                for instance in &model.instances {
+                    let model_m = model_matrix(instance.position, instance.yaw_rad, instance.scale);
+                    let view_model = mat4_mul(&view, &model_m);
+                    let mvp = mat4_mul(&proj, &view_model);
+                    draw_gpu_renderable(
+                        &gl,
+                        program,
+                        u_mvp.as_ref(),
+                        u_use_tex.as_ref(),
+                        u_tex.as_ref(),
+                        a_pos,
+                        a_uv,
+                        &model.gpu,
+                        &mvp,
+                    );
+                }
+            }
+        }
+
+        window.gl_swap_window();
+
+        fps_frames = fps_frames.saturating_add(1);
+        let elapsed = fps_window_start.elapsed();
+        if elapsed >= Duration::from_millis(500) {
+            let fps = fps_frames as f32 / elapsed.as_secs_f32().max(0.000_1);
+            let frame_time_ms = 1000.0 / fps.max(0.000_1);
+            let _ = window.set_title(&format!(
+                "Parkan Mission Demo | FPS: {fps:.1} ({frame_time_ms:.2} ms) | objects: {instance_count}"
+            ));
+            print!("\rFPS: {fps:.1} ({frame_time_ms:.2} ms)");
+            let _ = std::io::stdout().flush();
+            fps_printed = true;
+            fps_frames = 0;
+            fps_window_start = Instant::now();
+        }
+    }
+
+    if fps_printed {
+        println!();
+    }
+
+    unsafe {
+        cleanup_renderable(&gl, terrain_gpu);
+        for model in model_gpus {
+            cleanup_renderable(&gl, model.gpu);
+        }
+        gl.delete_program(program);
+    }
+
+    Ok(())
+}
+
+fn initial_scene_sphere(scene: &MissionScene) -> ([f32; 3], f32) {
+    if let Some((min_v, max_v)) = compute_scene_bounds(scene) {
+        let center = [
+            0.5 * (min_v[0] + max_v[0]),
+            0.5 * (min_v[1] + max_v[1]),
+            0.5 * (min_v[2] + max_v[2]),
+        ];
+        let extent = [
+            max_v[0] - min_v[0],
+            max_v[1] - min_v[1],
+            max_v[2] - min_v[2],
+        ];
+        let radius = ((extent[0] * extent[0]) + (extent[1] * extent[1]) + (extent[2] * extent[2]))
+            .sqrt()
+            .max(10.0)
+            * 0.5;
+        return (center, radius);
+    }
+    ([0.0, 0.0, 0.0], 100.0)
+}
+
+fn update_camera(events: &sdl2::EventPump, camera: &mut Camera, dt: f32) {
+    use sdl2::keyboard::Scancode;
+
+    let keys = events.keyboard_state();
+    let mut move_dir = [0.0f32, 0.0f32, 0.0f32];
+
+    let forward = camera_forward(camera.yaw, camera.pitch);
+    let right = normalize3(cross3(forward, [0.0, 1.0, 0.0]));
+
+    if keys.is_scancode_pressed(Scancode::Up) || keys.is_scancode_pressed(Scancode::W) {
+        move_dir[0] += forward[0];
+        move_dir[1] += forward[1];
+        move_dir[2] += forward[2];
+    }
+    if keys.is_scancode_pressed(Scancode::Down) || keys.is_scancode_pressed(Scancode::S) {
+        move_dir[0] -= forward[0];
+        move_dir[1] -= forward[1];
+        move_dir[2] -= forward[2];
+    }
+    if keys.is_scancode_pressed(Scancode::Left) || keys.is_scancode_pressed(Scancode::A) {
+        move_dir[0] -= right[0];
+        move_dir[1] -= right[1];
+        move_dir[2] -= right[2];
+    }
+    if keys.is_scancode_pressed(Scancode::Right) || keys.is_scancode_pressed(Scancode::D) {
+        move_dir[0] += right[0];
+        move_dir[1] += right[1];
+        move_dir[2] += right[2];
+    }
+    if keys.is_scancode_pressed(Scancode::PageUp) || keys.is_scancode_pressed(Scancode::E) {
+        move_dir[1] += 1.0;
+    }
+    if keys.is_scancode_pressed(Scancode::PageDown) || keys.is_scancode_pressed(Scancode::Q) {
+        move_dir[1] -= 1.0;
+    }
+
+    let shift =
+        keys.is_scancode_pressed(Scancode::LShift) || keys.is_scancode_pressed(Scancode::RShift);
+    let speed_mul = if shift { 3.0 } else { 1.0 };
+
+    let norm = normalize3(move_dir);
+    camera.position[0] += norm[0] * camera.move_speed * speed_mul * dt;
+    camera.position[1] += norm[1] * camera.move_speed * speed_mul * dt;
+    camera.position[2] += norm[2] * camera.move_speed * speed_mul * dt;
+}
+
+unsafe fn upload_model_renderable(
+    gl: &glow::Context,
+    model: &render_mission_demo::SceneModel,
+) -> Result<ModelRenderable, String> {
+    let mut vertex_data = Vec::with_capacity(model.mesh.vertices.len() * 5);
+    for vertex in &model.mesh.vertices {
+        vertex_data.push(vertex.position[0]);
+        vertex_data.push(vertex.position[1]);
+        vertex_data.push(vertex.position[2]);
+        vertex_data.push(vertex.uv0[0]);
+        vertex_data.push(vertex.uv0[1]);
+    }
+
+    let gpu = upload_gpu_renderable(
+        gl,
+        &vertex_data,
+        &model.mesh.indices,
+        model.texture.as_ref(),
+    )?;
+
+    Ok(ModelRenderable {
+        gpu,
+        instances: model.instances.clone(),
+    })
+}
+
+unsafe fn upload_terrain_renderable(
+    gl: &glow::Context,
+    mesh: &terrain_core::TerrainRenderMesh,
+    texture: Option<&render_demo::LoadedTexture>,
+) -> Result<GpuRenderable, String> {
+    let mut vertex_data = Vec::with_capacity(mesh.vertices.len() * 5);
+    for vertex in &mesh.vertices {
+        vertex_data.push(vertex.position[0]);
+        vertex_data.push(vertex.position[1]);
+        vertex_data.push(vertex.position[2]);
+        vertex_data.push(vertex.uv0[0]);
+        vertex_data.push(vertex.uv0[1]);
+    }
+
+    upload_gpu_renderable(gl, &vertex_data, &mesh.indices, texture)
+}
+
+unsafe fn upload_gpu_renderable(
+    gl: &glow::Context,
+    vertices: &[f32],
+    indices: &[u16],
+    texture: Option<&render_demo::LoadedTexture>,
+) -> Result<GpuRenderable, String> {
+    let vbo = gl.create_buffer().map_err(|e| e.to_string())?;
+    let ebo = gl.create_buffer().map_err(|e| e.to_string())?;
+
+    let vertex_bytes = f32_slice_to_ne_bytes(vertices);
+    let index_bytes = u16_slice_to_ne_bytes(indices);
+
+    gl.bind_buffer(glow::ARRAY_BUFFER, Some(vbo));
+    gl.buffer_data_u8_slice(glow::ARRAY_BUFFER, &vertex_bytes, glow::STATIC_DRAW);
+    gl.bind_buffer(glow::ELEMENT_ARRAY_BUFFER, Some(ebo));
+    gl.buffer_data_u8_slice(glow::ELEMENT_ARRAY_BUFFER, &index_bytes, glow::STATIC_DRAW);
+    gl.bind_buffer(glow::ELEMENT_ARRAY_BUFFER, None);
+    gl.bind_buffer(glow::ARRAY_BUFFER, None);
+
+    let gpu_texture = if let Some(texture) = texture {
+        Some(create_texture(gl, texture)?)
+    } else {
+        None
+    };
+
+    Ok(GpuRenderable {
+        vbo,
+        ebo,
+        index_count: indices.len(),
+        texture: gpu_texture,
+    })
+}
+
+unsafe fn cleanup_renderable(gl: &glow::Context, renderable: GpuRenderable) {
+    if let Some(tex) = renderable.texture {
+        gl.delete_texture(tex.handle);
+    }
+    gl.delete_buffer(renderable.ebo);
+    gl.delete_buffer(renderable.vbo);
+}
+
+unsafe fn draw_frame_begin(gl: &glow::Context, width: u32, height: u32) {
+    gl.viewport(
+        0,
+        0,
+        width.min(i32::MAX as u32) as i32,
+        height.min(i32::MAX as u32) as i32,
+    );
+    gl.enable(glow::DEPTH_TEST);
+    gl.clear_color(0.06, 0.08, 0.12, 1.0);
+    gl.clear(glow::COLOR_BUFFER_BIT | glow::DEPTH_BUFFER_BIT);
+}
+
+unsafe fn draw_gpu_renderable(
+    gl: &glow::Context,
+    program: glow::NativeProgram,
+    u_mvp: Option<&glow::NativeUniformLocation>,
+    u_use_tex: Option<&glow::NativeUniformLocation>,
+    u_tex: Option<&glow::NativeUniformLocation>,
+    a_pos: u32,
+    a_uv: u32,
+    renderable: &GpuRenderable,
+    mvp: &[f32; 16],
+) {
+    gl.use_program(Some(program));
+    gl.uniform_matrix_4_f32_slice(u_mvp, false, mvp);
+
+    let texture_enabled = renderable.texture.is_some();
+    gl.uniform_1_f32(u_use_tex, if texture_enabled { 1.0 } else { 0.0 });
+
+    if let Some(tex) = &renderable.texture {
+        gl.active_texture(glow::TEXTURE0);
+        gl.bind_texture(glow::TEXTURE_2D, Some(tex.handle));
+        gl.uniform_1_i32(u_tex, 0);
+    } else {
+        gl.bind_texture(glow::TEXTURE_2D, None);
+    }
+
+    gl.bind_buffer(glow::ARRAY_BUFFER, Some(renderable.vbo));
+    gl.bind_buffer(glow::ELEMENT_ARRAY_BUFFER, Some(renderable.ebo));
+    gl.enable_vertex_attrib_array(a_pos);
+    gl.vertex_attrib_pointer_f32(a_pos, 3, glow::FLOAT, false, 20, 0);
+    gl.enable_vertex_attrib_array(a_uv);
+    gl.vertex_attrib_pointer_f32(a_uv, 2, glow::FLOAT, false, 20, 12);
+
+    gl.draw_elements(
+        glow::TRIANGLES,
+        renderable.index_count.min(i32::MAX as usize) as i32,
+        glow::UNSIGNED_SHORT,
+        0,
+    );
+
+    gl.disable_vertex_attrib_array(a_uv);
+    gl.disable_vertex_attrib_array(a_pos);
+    gl.bind_buffer(glow::ELEMENT_ARRAY_BUFFER, None);
+    gl.bind_buffer(glow::ARRAY_BUFFER, None);
+    gl.bind_texture(glow::TEXTURE_2D, None);
+    gl.use_program(None);
+}
+
+fn create_window_and_context(
+    video: &sdl2::VideoSubsystem,
+    width: u32,
+    height: u32,
+) -> Result<(sdl2::video::Window, sdl2::video::GLContext, GlBackend), String> {
+    let candidates = [
+        (GlBackend::Gles2, sdl2::video::GLProfile::GLES, 2, 0),
+        (GlBackend::Core33, sdl2::video::GLProfile::Core, 3, 3),
+    ];
+    let mut errors = Vec::new();
+
+    for (backend, profile, major, minor) in candidates {
+        {
+            let gl_attr = video.gl_attr();
+            gl_attr.set_context_profile(profile);
+            gl_attr.set_context_version(major, minor);
+            gl_attr.set_depth_size(24);
+            gl_attr.set_double_buffer(true);
+        }
+
+        let mut window_builder = video.window("Parkan Mission Demo", width, height);
+        window_builder.opengl().resizable();
+
+        let window = match window_builder.build() {
+            Ok(window) => window,
+            Err(err) => {
+                errors.push(format!(
+                    "{profile:?} {major}.{minor}: window build failed ({err})"
+                ));
+                continue;
+            }
+        };
+
+        let gl_ctx = match window.gl_create_context() {
+            Ok(ctx) => ctx,
+            Err(err) => {
+                errors.push(format!(
+                    "{profile:?} {major}.{minor}: context create failed ({err})"
+                ));
+                continue;
+            }
+        };
+
+        if let Err(err) = window.gl_make_current(&gl_ctx) {
+            errors.push(format!(
+                "{profile:?} {major}.{minor}: make current failed ({err})"
+            ));
+            continue;
+        }
+
+        return Ok((window, gl_ctx, backend));
+    }
+
+    Err(format!(
+        "failed to create OpenGL context. Attempts: {}",
+        errors.join(" | ")
+    ))
+}
+
+unsafe fn create_texture(
+    gl: &glow::Context,
+    texture: &render_demo::LoadedTexture,
+) -> Result<GpuTexture, String> {
+    let handle = gl.create_texture().map_err(|e| e.to_string())?;
+    gl.bind_texture(glow::TEXTURE_2D, Some(handle));
+    gl.tex_parameter_i32(
+        glow::TEXTURE_2D,
+        glow::TEXTURE_MIN_FILTER,
+        glow::LINEAR as i32,
+    );
+    gl.tex_parameter_i32(
+        glow::TEXTURE_2D,
+        glow::TEXTURE_MAG_FILTER,
+        glow::LINEAR as i32,
+    );
+    gl.tex_parameter_i32(glow::TEXTURE_2D, glow::TEXTURE_WRAP_S, glow::REPEAT as i32);
+    gl.tex_parameter_i32(glow::TEXTURE_2D, glow::TEXTURE_WRAP_T, glow::REPEAT as i32);
+    gl.pixel_store_i32(glow::UNPACK_ALIGNMENT, 1);
+    gl.tex_image_2d(
+        glow::TEXTURE_2D,
+        0,
+        glow::RGBA as i32,
+        texture.width.min(i32::MAX as u32) as i32,
+        texture.height.min(i32::MAX as u32) as i32,
+        0,
+        glow::RGBA,
+        glow::UNSIGNED_BYTE,
+        glow::PixelUnpackData::Slice(Some(texture.rgba8.as_slice())),
+    );
+    gl.bind_texture(glow::TEXTURE_2D, None);
+    Ok(GpuTexture { handle })
+}
+
+unsafe fn create_program(
+    gl: &glow::Context,
+    backend: GlBackend,
+) -> Result<glow::NativeProgram, String> {
+    let (vs_src, fs_src) = match backend {
+        GlBackend::Gles2 => (
+            r#"
+attribute vec3 a_pos;
+attribute vec2 a_uv;
+uniform mat4 u_mvp;
+varying vec2 v_uv;
+void main() {
+    v_uv = a_uv;
+    gl_Position = u_mvp * vec4(a_pos, 1.0);
+}
+"#,
+            r#"
+precision mediump float;
+uniform sampler2D u_tex;
+uniform float u_use_tex;
+varying vec2 v_uv;
+void main() {
+    vec4 base = vec4(0.82, 0.87, 0.95, 1.0);
+    vec4 texColor = texture2D(u_tex, v_uv);
+    gl_FragColor = mix(base, texColor, u_use_tex);
+}
+"#,
+        ),
+        GlBackend::Core33 => (
+            r#"#version 330 core
+in vec3 a_pos;
+in vec2 a_uv;
+uniform mat4 u_mvp;
+out vec2 v_uv;
+void main() {
+    v_uv = a_uv;
+    gl_Position = u_mvp * vec4(a_pos, 1.0);
+}
+"#,
+            r#"#version 330 core
+uniform sampler2D u_tex;
+uniform float u_use_tex;
+in vec2 v_uv;
+out vec4 fragColor;
+void main() {
+    vec4 base = vec4(0.82, 0.87, 0.95, 1.0);
+    vec4 texColor = texture(u_tex, v_uv);
+    fragColor = mix(base, texColor, u_use_tex);
+}
+"#,
+        ),
+    };
+
+    let program = gl.create_program().map_err(|e| e.to_string())?;
+    let vs = gl
+        .create_shader(glow::VERTEX_SHADER)
+        .map_err(|e| e.to_string())?;
+    let fs = gl
+        .create_shader(glow::FRAGMENT_SHADER)
+        .map_err(|e| e.to_string())?;
+
+    gl.shader_source(vs, vs_src);
+    gl.compile_shader(vs);
+    if !gl.get_shader_compile_status(vs) {
+        let log = gl.get_shader_info_log(vs);
+        gl.delete_shader(vs);
+        gl.delete_shader(fs);
+        gl.delete_program(program);
+        return Err(format!("vertex shader compile failed: {log}"));
+    }
+
+    gl.shader_source(fs, fs_src);
+    gl.compile_shader(fs);
+    if !gl.get_shader_compile_status(fs) {
+        let log = gl.get_shader_info_log(fs);
+        gl.delete_shader(vs);
+        gl.delete_shader(fs);
+        gl.delete_program(program);
+        return Err(format!("fragment shader compile failed: {log}"));
+    }
+
+    gl.attach_shader(program, vs);
+    gl.attach_shader(program, fs);
+    gl.link_program(program);
+
+    gl.detach_shader(program, vs);
+    gl.detach_shader(program, fs);
+    gl.delete_shader(vs);
+    gl.delete_shader(fs);
+
+    if !gl.get_program_link_status(program) {
+        let log = gl.get_program_info_log(program);
+        gl.delete_program(program);
+        return Err(format!("program link failed: {log}"));
+    }
+
+    Ok(program)
+}
+
+fn model_matrix(position: [f32; 3], yaw: f32, scale: [f32; 3]) -> [f32; 16] {
+    let translation = mat4_translation(position[0], position[1], position[2]);
+    let rotation = mat4_rotation_y(yaw);
+    let scaling = mat4_scale(scale[0], scale[1], scale[2]);
+    let tr = mat4_mul(&translation, &rotation);
+    mat4_mul(&tr, &scaling)
+}
+
+fn camera_forward(yaw: f32, pitch: f32) -> [f32; 3] {
+    let cp = pitch.cos();
+    normalize3([yaw.sin() * cp, pitch.sin(), yaw.cos() * cp])
+}
+
+fn cross3(a: [f32; 3], b: [f32; 3]) -> [f32; 3] {
+    [
+        a[1] * b[2] - a[2] * b[1],
+        a[2] * b[0] - a[0] * b[2],
+        a[0] * b[1] - a[1] * b[0],
+    ]
+}
+
+fn dot3(a: [f32; 3], b: [f32; 3]) -> f32 {
+    a[0] * b[0] + a[1] * b[1] + a[2] * b[2]
+}
+
+fn normalize3(v: [f32; 3]) -> [f32; 3] {
+    let len = (v[0] * v[0] + v[1] * v[1] + v[2] * v[2]).sqrt();
+    if len <= 1e-6 {
+        [0.0, 0.0, 0.0]
+    } else {
+        [v[0] / len, v[1] / len, v[2] / len]
+    }
+}
+
+fn mat4_identity() -> [f32; 16] {
+    [
+        1.0, 0.0, 0.0, 0.0, //
+        0.0, 1.0, 0.0, 0.0, //
+        0.0, 0.0, 1.0, 0.0, //
+        0.0, 0.0, 0.0, 1.0, //
+    ]
+}
+
+fn mat4_translation(x: f32, y: f32, z: f32) -> [f32; 16] {
+    let mut m = mat4_identity();
+    m[12] = x;
+    m[13] = y;
+    m[14] = z;
+    m
+}
+
+fn mat4_scale(x: f32, y: f32, z: f32) -> [f32; 16] {
+    [
+        x, 0.0, 0.0, 0.0, //
+        0.0, y, 0.0, 0.0, //
+        0.0, 0.0, z, 0.0, //
+        0.0, 0.0, 0.0, 1.0, //
+    ]
+}
+
+fn mat4_rotation_y(rad: f32) -> [f32; 16] {
+    let c = rad.cos();
+    let s = rad.sin();
+    [
+        c, 0.0, -s, 0.0, //
+        0.0, 1.0, 0.0, 0.0, //
+        s, 0.0, c, 0.0, //
+        0.0, 0.0, 0.0, 1.0, //
+    ]
+}
+
+fn mat4_perspective(fovy: f32, aspect: f32, near: f32, far: f32) -> [f32; 16] {
+    let f = 1.0 / (0.5 * fovy).tan();
+    let nf = 1.0 / (near - far);
+    [
+        f / aspect,
+        0.0,
+        0.0,
+        0.0,
+        0.0,
+        f,
+        0.0,
+        0.0,
+        0.0,
+        0.0,
+        (far + near) * nf,
+        -1.0,
+        0.0,
+        0.0,
+        (2.0 * far * near) * nf,
+        0.0,
+    ]
+}
+
+fn mat4_look_at(eye: [f32; 3], target: [f32; 3], up: [f32; 3]) -> [f32; 16] {
+    let f = normalize3([target[0] - eye[0], target[1] - eye[1], target[2] - eye[2]]);
+    let s = normalize3(cross3(f, up));
+    let u = cross3(s, f);
+
+    [
+        s[0],
+        u[0],
+        -f[0],
+        0.0,
+        s[1],
+        u[1],
+        -f[1],
+        0.0,
+        s[2],
+        u[2],
+        -f[2],
+        0.0,
+        -dot3(s, eye),
+        -dot3(u, eye),
+        dot3(f, eye),
+        1.0,
+    ]
+}
+
+fn mat4_mul(a: &[f32; 16], b: &[f32; 16]) -> [f32; 16] {
+    let mut out = [0.0f32; 16];
+    for c in 0..4 {
+        for r in 0..4 {
+            let mut acc = 0.0f32;
+            for k in 0..4 {
+                acc += a[k * 4 + r] * b[c * 4 + k];
+            }
+            out[c * 4 + r] = acc;
+        }
+    }
+    out
+}
+
+fn f32_slice_to_ne_bytes(slice: &[f32]) -> Vec<u8> {
+    let mut out = Vec::with_capacity(slice.len().saturating_mul(std::mem::size_of::<f32>()));
+    for &value in slice {
+        out.extend_from_slice(&value.to_ne_bytes());
+    }
+    out
+}
+
+fn u16_slice_to_ne_bytes(slice: &[u16]) -> Vec<u8> {
+    let mut out = Vec::with_capacity(slice.len().saturating_mul(std::mem::size_of::<u16>()));
+    for &value in slice {
+        out.extend_from_slice(&value.to_ne_bytes());
+    }
+    out
+}