Fix material categories and transparent background ordering

6 files changed, 496 insertions, 53 deletions

diff --git a/adapters/fparkan-render-vulkan/src/ffi/smoke.rs b/adapters/fparkan-render-vulkan/src/ffi/smoke.rs
index e8e18ac..c3565e1 100644
--- a/adapters/fparkan-render-vulkan/src/ffi/smoke.rs
+++ b/adapters/fparkan-render-vulkan/src/ffi/smoke.rs
@@ -1,7 +1,7 @@
 #![allow(unsafe_code)]
 
 use ash::vk;
-use fparkan_render::LegacyDepthMode;
+use fparkan_render::{LegacyDepthMode, LegacyPipelineState};
 
 use super::smoke_types::resolve_draw_texture_indices;
 use super::update_material_texture_descriptor;
@@ -434,6 +434,7 @@ impl VulkanSmokeRenderer {
             draw_range_sort_keys: vec![None; create_info.mesh.draw_ranges.len()],
             draw_order_dirty: false,
             draw_range_world_queue: vec![None; create_info.mesh.draw_ranges.len()],
+            world_transparent_background_ranges: Vec::new(),
             draw_range_base_pipeline_states: create_info
                 .mesh
                 .draw_ranges
@@ -878,6 +879,74 @@ impl VulkanSmokeRenderer {
         Ok(())
     }
 
+    /// Applies the active MAT0 phase's blend and alpha-test category to one
+    /// range while retaining its authored depth and cull state.
+    pub fn set_draw_range_material_category(
+        &mut self,
+        range_index: usize,
+        category: u8,
+    ) -> Result<(), VulkanSmokeRendererError> {
+        let base_state = *self
+            .draw_range_base_pipeline_states
+            .get(range_index)
+            .ok_or(VulkanSmokeRendererError::InvalidStaticMesh {
+                context: "dynamic draw range index is out of bounds",
+            })?;
+        let world_queue = self
+            .draw_range_world_queue
+            .get(range_index)
+            .copied()
+            .ok_or(VulkanSmokeRendererError::InvalidStaticMesh {
+                context: "dynamic draw range index is out of bounds",
+            })?;
+        // Fixed sky, sprite, weather, and shadow ranges own explicit states.
+        // MAT0 categories apply only after a range has entered the world queue.
+        let (next_base, next_state) =
+            world_material_pipeline_states(base_state, category, world_queue).ok_or(
+                VulkanSmokeRendererError::InvalidStaticMesh {
+                    context: "MAT0 pipeline category is outside the native 0..=4 table",
+                },
+            )?;
+        let range = self.draw_ranges.get_mut(range_index).ok_or(
+            VulkanSmokeRendererError::InvalidStaticMesh {
+                context: "dynamic draw range index is out of bounds",
+            },
+        )?;
+        self.draw_range_base_pipeline_states[range_index] = next_base;
+        let pipeline_changed = range.pipeline_state != next_state;
+        range.pipeline_state = next_state;
+        if pipeline_changed {
+            self.rebuild_pipeline_resources()?;
+        }
+        Ok(())
+    }
+
+    /// Places nebula, dome, and cloud ranges between opaque and transparent
+    /// world draws. The list is explicit so unrelated fixed passes keep their
+    /// established order.
+    pub fn set_world_transparent_background_ranges(
+        &mut self,
+        range_indices: &[usize],
+    ) -> Result<(), VulkanSmokeRendererError> {
+        let mut seen = vec![false; self.draw_ranges.len()];
+        for &range_index in range_indices {
+            let Some(slot) = seen.get_mut(range_index) else {
+                return Err(VulkanSmokeRendererError::InvalidStaticMesh {
+                    context: "world background range index is out of bounds",
+                });
+            };
+            if *slot || self.draw_range_world_queue[range_index].is_some() {
+                return Err(VulkanSmokeRendererError::InvalidStaticMesh {
+                    context: "world background range is duplicated or already queued",
+                });
+            }
+            *slot = true;
+        }
+        self.world_transparent_background_ranges = range_indices.to_vec();
+        self.draw_order_dirty = true;
+        Ok(())
+    }
+
     /// Marks a draw range as belonging to the native transparent queue.
     ///
     /// The flag is deliberately independent of the blend category: native
@@ -886,14 +955,25 @@ impl VulkanSmokeRenderer {
     /// depth attachment switches to depth-test/read-only.  The original depth
     /// state is retained so disabling the flag restores the caller's state.
     ///
-    /// The transparent flag only participates in the world draw order.  The
-    /// backend keeps every unmarked range in its original slot, which leaves
-    /// the fixed screen/sky/weather pass order intact.
+    /// The transparent flag only participates in the world draw order. Without
+    /// explicit backgrounds, opaque and transparent ranges replace the
+    /// existing world slots. With explicit backgrounds, opaque ranges compact
+    /// into those slots and the sorted transparent ranges are inserted after
+    /// the last background; unrelated fixed ranges keep relative order but
+    /// may shift slots.
     pub fn set_draw_range_transparency(
         &mut self,
         range_index: usize,
         transparent: bool,
     ) -> Result<(), VulkanSmokeRendererError> {
+        if self
+            .world_transparent_background_ranges
+            .contains(&range_index)
+        {
+            return Err(VulkanSmokeRendererError::InvalidStaticMesh {
+                context: "world background range cannot join the world queue",
+            });
+        }
         let base_state = *self
             .draw_range_base_pipeline_states
             .get(range_index)
@@ -905,13 +985,7 @@ impl VulkanSmokeRenderer {
                 context: "dynamic draw range index is out of bounds",
             },
         )?;
-        let depth = if transparent && base_state.depth != LegacyDepthMode::Disabled {
-            LegacyDepthMode::TestReadOnly
-        } else {
-            base_state.depth
-        };
-        let mut next_state = base_state;
-        next_state.depth = depth;
+        let next_state = apply_world_transparency(base_state, transparent);
         let pipeline_changed = range.pipeline_state != next_state;
         range.pipeline_state = next_state;
         // Calling this setter opts the range into the world queue.  Fixed
@@ -1499,11 +1573,13 @@ impl VulkanSmokeRenderer {
         self.rebuild_swapchain_resources(true)
     }
 
-    /// Recomputes the stable command-recording order.  Only ranges explicitly
-    /// marked transparent are reordered, and they remain in the slots occupied
-    /// by that queue.  This preserves the caller's fixed sky/screen/weather
-    /// pass order while matching the native descending key comparator for the
-    /// world transparent queue.
+    /// Recomputes the stable command-recording order. Without explicit
+    /// backgrounds, opaque world ranges followed by the sorted transparent
+    /// world ranges replace the existing world slots. With explicit
+    /// backgrounds, opaque ranges compact into the world slots and sorted
+    /// transparent ranges are inserted after the last background; unrelated
+    /// fixed ranges keep relative order but may shift slots. The transparent
+    /// queue matches the native descending key comparator.
     fn rebuild_draw_order(&mut self) {
         let range_count = self.draw_ranges.len();
         if self.draw_order.len() != range_count {
@@ -1514,6 +1590,7 @@ impl VulkanSmokeRenderer {
             &self.draw_ranges,
             &self.draw_range_world_queue,
             &self.draw_range_sort_keys,
+            &self.world_transparent_background_ranges,
         );
     }
 
@@ -2109,15 +2186,46 @@ fn apply_geometry_range_updates(
     }
 }
 
+fn apply_world_transparency(
+    base_state: LegacyPipelineState,
+    transparent: bool,
+) -> LegacyPipelineState {
+    if transparent && base_state.depth != LegacyDepthMode::Disabled {
+        LegacyPipelineState {
+            depth: LegacyDepthMode::TestReadOnly,
+            ..base_state
+        }
+    } else {
+        base_state
+    }
+}
+
+fn world_material_pipeline_states(
+    original: LegacyPipelineState,
+    category: u8,
+    world_queue: Option<bool>,
+) -> Option<(LegacyPipelineState, LegacyPipelineState)> {
+    let categorized = original.with_material_category(category)?;
+    let Some(transparent) = world_queue else {
+        return Some((original, original));
+    };
+    let base = categorized;
+    Some((base, apply_world_transparency(base, transparent)))
+}
+
 /// Replays the native queue construction from the original stable range
-/// order. Fixed passes stay in their original slots; world opaque ranges are
-/// emitted first, followed by world transparent ranges inserted by descending
-/// camera distance. Zero-index-count ranges are inactive and are omitted.
+/// order. Without explicit background ranges, world opaque ranges replace the
+/// existing world slots and world transparent ranges follow in descending
+/// camera distance order. With explicit backgrounds, opaque ranges are
+/// compacted into world positions and sorted transparent ranges are inserted
+/// after the last active background; fixed passes keep their relative order but
+/// can shift slots. Zero-index-count ranges are inactive and are omitted.
 fn sorted_world_draw_order(
     range_count: usize,
     ranges: &[super::VulkanStaticDrawRange],
     world_queue: &[Option<bool>],
     keys: &[Option<f32>],
+    transparent_background_ranges: &[usize],
 ) -> Vec<usize> {
     let mut next = (0..range_count).collect::<Vec<_>>();
     let mut world_opaque = Vec::new();
@@ -2176,33 +2284,70 @@ fn sorted_world_draw_order(
         ordered_transparent.insert(low, range_index);
     }
 
-    let mut world_order = world_opaque;
-    world_order.extend(ordered_transparent);
-    let mut world_cursor = 0usize;
-    for slot in &mut next {
-        if world_queue.get(*slot).copied().flatten().is_some()
-            && ranges
-                .get(*slot)
-                .is_some_and(|range| range.index_count != 0)
-        {
-            if let Some(&replacement) = world_order.get(world_cursor) {
-                *slot = replacement;
-                world_cursor += 1;
+    if transparent_background_ranges.is_empty() {
+        let mut world_order = world_opaque;
+        world_order.extend(ordered_transparent);
+        let mut world_cursor = 0usize;
+        for slot in &mut next {
+            if world_queue.get(*slot).copied().flatten().is_some()
+                && ranges
+                    .get(*slot)
+                    .is_some_and(|range| range.index_count != 0)
+            {
+                if let Some(&replacement) = world_order.get(world_cursor) {
+                    *slot = replacement;
+                    world_cursor += 1;
+                }
             }
         }
+        return next;
+    }
+
+    // Fixed sky backgrounds are not world-queue members. Remove the world
+    // transparent slots, compact opaque ranges into the world slots, then
+    // insert the sorted transparent queue after the explicit background group.
+    let mut opaque_cursor = 0usize;
+    let mut next_without_transparency = Vec::with_capacity(range_count);
+    for slot in 0..range_count {
+        let active_world = ranges.get(slot).is_some_and(|range| range.index_count != 0);
+        match world_queue.get(slot).copied().flatten() {
+            Some(true) if active_world => {}
+            Some(false) if active_world => {
+                if let Some(&replacement) = world_opaque.get(opaque_cursor) {
+                    next_without_transparency.push(replacement);
+                    opaque_cursor += 1;
+                } else {
+                    next_without_transparency.push(slot);
+                }
+            }
+            _ => next_without_transparency.push(slot),
+        }
     }
-    next
+    let insertion = transparent_background_ranges
+        .iter()
+        .filter_map(|background| {
+            next_without_transparency
+                .iter()
+                .position(|range| range == background)
+        })
+        .max()
+        .map(|index| index + 1);
+    if let Some(insertion) = insertion {
+        next_without_transparency.splice(insertion..insertion, ordered_transparent);
+    }
+    next_without_transparency
 }
 
 #[cfg(test)]
 mod tests {
     use super::super::{VulkanDynamicDrawRange, VulkanStaticDrawRange, VulkanStaticMesh};
     use super::{
-        apply_geometry_range_updates, completed_readback_buffer_index, sorted_world_draw_order,
-        take_runtime_children_with_validation_snapshot, take_runtime_owners_in_dependency_order,
-        validate_geometry_upload, RollbackOnDrop,
+        apply_geometry_range_updates, apply_world_transparency, completed_readback_buffer_index,
+        sorted_world_draw_order, take_runtime_children_with_validation_snapshot,
+        take_runtime_owners_in_dependency_order, validate_geometry_upload,
+        world_material_pipeline_states, RollbackOnDrop,
     };
-    use fparkan_render::{LegacyBlendMode, LegacyDepthMode, LegacyPipelineState};
+    use fparkan_render::{LegacyBlendMode, LegacyCullMode, LegacyDepthMode, LegacyPipelineState};
     use std::cell::RefCell;
     use std::rc::Rc;
 
@@ -2506,6 +2651,7 @@ mod tests {
             &ranges,
             &[None, Some(true), None, Some(true), Some(false)],
             &[None, Some(2.0), None, Some(9.0), Some(-3.0)],
+            &[],
         );
         assert_eq!(order, vec![0, 4, 2, 3, 1]);
     }
@@ -2546,6 +2692,7 @@ mod tests {
             &ranges,
             &[None, Some(true), Some(true)],
             &[None, Some(100.0), Some(1.0)],
+            &[],
         );
         assert_eq!(order, vec![0, 1, 2]);
     }
@@ -2563,7 +2710,99 @@ mod tests {
                 alpha_test_reference: 0,
             })
             .collect::<Vec<_>>();
-        let order = sorted_world_draw_order(4, &ranges, &[Some(true); 4], &[Some(1.0); 4]);
+        let order = sorted_world_draw_order(4, &ranges, &[Some(true); 4], &[Some(1.0); 4], &[]);
         assert_eq!(order, vec![2, 3, 1, 0]);
     }
+
+    #[test]
+    fn tree_canopy_queue_follows_sky_and_precedes_foreground_effects() {
+        const SCREEN_GRADIENT: usize = 0;
+        const TERRAIN: usize = 1;
+        const CANOPY_NEAR: usize = 2;
+        const BUILDING: usize = 3;
+        const CANOPY_FAR: usize = 4;
+        const SHADOW: usize = 5;
+        const NEBULA: usize = 6;
+        const DOME: usize = 7;
+        const CLOUDS: usize = 8;
+        const SUN: usize = 9;
+        const WEATHER: usize = 10;
+        let ranges = (0..11)
+            .map(|index| VulkanStaticDrawRange {
+                first_index: index * 3,
+                index_count: 3,
+                material_index: 0,
+                lightmap_index: u8::MAX,
+                batch_flags: 0,
+                pipeline_state: LegacyPipelineState::default(),
+                alpha_test_reference: 0,
+            })
+            .collect::<Vec<_>>();
+        let mut world_queue = vec![None; ranges.len()];
+        world_queue[TERRAIN] = Some(false);
+        world_queue[CANOPY_NEAR] = Some(true);
+        world_queue[BUILDING] = Some(false);
+        world_queue[CANOPY_FAR] = Some(true);
+        let mut sort_keys = vec![None; ranges.len()];
+        sort_keys[CANOPY_NEAR] = Some(2.0);
+        sort_keys[CANOPY_FAR] = Some(9.0);
+        let order = sorted_world_draw_order(
+            ranges.len(),
+            &ranges,
+            &world_queue,
+            &sort_keys,
+            &[NEBULA, DOME, CLOUDS],
+        );
+        assert_eq!(
+            order,
+            vec![
+                SCREEN_GRADIENT,
+                TERRAIN,
+                BUILDING,
+                SHADOW,
+                NEBULA,
+                DOME,
+                CLOUDS,
+                CANOPY_FAR,
+                CANOPY_NEAR,
+                SUN,
+                WEATHER,
+            ]
+        );
+    }
+
+    #[test]
+    fn material_category_and_transparency_preserve_world_state_in_either_order() {
+        let original = LegacyPipelineState {
+            blend: LegacyBlendMode::Opaque,
+            depth: LegacyDepthMode::TestWrite,
+            cull: LegacyCullMode::FrontFace,
+            alpha_test: false,
+        };
+        let (base, category_first) =
+            world_material_pipeline_states(original, 1, Some(true)).expect("category 1");
+        let transparency_first = apply_world_transparency(original, true)
+            .with_material_category(1)
+            .expect("category 1 after transparency");
+        assert_eq!(category_first, transparency_first);
+        assert_eq!(base.blend, LegacyBlendMode::SourceAlpha);
+        assert!(base.alpha_test);
+        assert_eq!(base.depth, LegacyDepthMode::TestWrite);
+        assert_eq!(base.cull, LegacyCullMode::FrontFace);
+        assert_eq!(category_first.depth, LegacyDepthMode::TestReadOnly);
+        assert_eq!(category_first.cull, LegacyCullMode::FrontFace);
+
+        let fixed_state = LegacyPipelineState {
+            blend: LegacyBlendMode::Additive,
+            depth: LegacyDepthMode::Disabled,
+            cull: LegacyCullMode::Disabled,
+            alpha_test: false,
+        };
+        assert_eq!(
+            world_material_pipeline_states(fixed_state, 1, None),
+            Some((fixed_state, fixed_state))
+        );
+        assert!(world_material_pipeline_states(original, 5, Some(false)).is_none());
+        assert!(world_material_pipeline_states(fixed_state, 5, None).is_none());
+    }
 }
diff --git a/adapters/fparkan-render-vulkan/src/ffi/smoke_types.rs b/adapters/fparkan-render-vulkan/src/ffi/smoke_types.rs
index 75877ad..c41eff9 100644
--- a/adapters/fparkan-render-vulkan/src/ffi/smoke_types.rs
+++ b/adapters/fparkan-render-vulkan/src/ffi/smoke_types.rs
@@ -449,6 +449,8 @@ impl VulkanStaticDrawRange {
 pub struct VulkanStaticMaterial {
     /// Positional material selector used by one or more source batches.
     pub material_index: u16,
+    /// Native MAT0 pipeline category selected for this phase (0..=4).
+    pub pipeline_category: u8,
     /// Decoded RGBA8 diffuse texture for this selector.
     pub texture: VulkanStaticTexture,
     /// Phase parameters 4..6, normalized directional light RGB coefficient.
@@ -1003,6 +1005,7 @@ mod static_mesh_tests {
         let materials = [
             VulkanStaticMaterial {
                 material_index: 2,
+                pipeline_category: 0,
                 texture: texture(),
                 detail_texture: None,
                 overlay_texture: None,
@@ -1028,6 +1031,7 @@ mod static_mesh_tests {
             },
             VulkanStaticMaterial {
                 material_index: 7,
+                pipeline_category: 0,
                 texture: texture(),
                 detail_texture: None,
                 overlay_texture: None,
@@ -1379,6 +1383,8 @@ pub struct VulkanSmokeRenderer {
     /// a fixed screen/sky/weather pass; `Some(false)` is world opaque and
     /// `Some(true)` is world transparent.
     pub(super) draw_range_world_queue: Vec<Option<bool>>,
+    /// Fixed sky background ranges placed between world opaque and transparent.
+    pub(super) world_transparent_background_ranges: Vec<usize>,
     /// Pipeline state before transparent queue depth policy is applied.
     pub(super) draw_range_base_pipeline_states: Vec<LegacyPipelineState>,
     pub(super) material_alphas: Vec<[f32; 2]>,
diff --git a/apps/fparkan-game/src/main.rs b/apps/fparkan-game/src/main.rs
index c974b6b..abfb6da 100644
--- a/apps/fparkan-game/src/main.rs
+++ b/apps/fparkan-game/src/main.rs
@@ -657,6 +657,7 @@ impl MaterialPhaseBinding {
 struct MaterialVariantSet {
     phase_material_indices: Vec<usize>,
     range_indices: Vec<usize>,
+    pipeline_category: u8,
 }
 
 #[derive(Clone, Debug)]
@@ -676,6 +677,19 @@ struct ActiveMaterialState {
     diffuse_alpha: f32,
 }
 
+fn selected_material_phase(
+    variant: &MaterialVariantSet,
+    phase_index: usize,
+    pipeline_category_for: impl FnOnce(usize) -> Option<u8>,
+) -> Result<(usize, u8), String> {
+    let material_index = selected_material_variant_index(variant, phase_index)
+        .ok_or_else(|| "MAT0 material animation has no texture variant".to_string())?;
+    let pipeline_category = pipeline_category_for(material_index).ok_or_else(|| {
+        format!("MAT0 material animation selector {material_index} is out of bounds")
+    })?;
+    Ok((material_index, pipeline_category))
+}
+
 fn update_material_animations(
     bindings: &mut [MaterialAnimationBinding],
     materials: &[VulkanStaticMaterial],
@@ -706,9 +720,13 @@ fn update_material_animations(
             .map(|overlay_detail| overlay_detail.sample(binding.initial_phase_index, clock_ms))
             .transpose()?;
         let mut updated_materials = HashSet::new();
-        for variant in &binding.variants {
-            let material_index = selected_material_variant_index(variant, base_sample.phase_index)
-                .ok_or_else(|| "MAT0 material animation has no texture variant".to_string())?;
+        for variant in &mut binding.variants {
+            let (material_index, pipeline_category) =
+                selected_material_phase(variant, base_sample.phase_index, |index| {
+                    materials
+                        .get(index)
+                        .map(|material| material.pipeline_category)
+                })?;
             for &range_index in &variant.range_indices {
                 active_materials.insert(
                     range_index,
@@ -720,7 +738,15 @@ fn update_material_animations(
                 renderer
                     .set_draw_range_material(range_index, material_index)
                     .map_err(|error| format!("update MAT0 material draw selector: {error}"))?;
+                if variant.pipeline_category != pipeline_category {
+                    renderer
+                        .set_draw_range_material_category(range_index, pipeline_category)
+                        .map_err(|error| {
+                            format!("update MAT0 material pipeline category: {error}")
+                        })?;
+                }
             }
+            variant.pipeline_category = pipeline_category;
             if !updated_materials.insert(material_index) {
                 continue;
             }
@@ -887,6 +913,37 @@ fn native_world_transparent(range: &VulkanStaticDrawRange, diffuse_alpha: f32) -
     diffuse_alpha < 1.0 || (range.batch_flags & 0x108) != 0
 }
 
+fn configure_world_material_categories(
+    mesh: &mut VulkanStaticMesh,
+    materials: &[VulkanStaticMaterial],
+    world_range_indices: &[usize],
+) -> Result<(), String> {
+    for &range_index in world_range_indices {
+        let range = mesh
+            .draw_ranges
+            .get_mut(range_index)
+            .ok_or_else(|| "world material range index is out of bounds".to_string())?;
+        let material = materials
+            .get(usize::from(range.material_index))
+            .ok_or_else(|| {
+                format!(
+                    "world material selector {} is out of bounds",
+                    range.material_index
+                )
+            })?;
+        range.pipeline_state = range
+            .pipeline_state
+            .with_material_category(material.pipeline_category)
+            .ok_or_else(|| {
+                format!(
+                    "world material selector {} has unsupported native pipeline category {}",
+                    range.material_index, material.pipeline_category
+                )
+            })?;
+    }
+    Ok(())
+}
+
 fn register_material_range(
     bindings: &mut [MaterialAnimationBinding],
     material_index: usize,
@@ -1164,6 +1221,7 @@ fn append_environment_material(
         })?;
         materials.push(VulkanStaticMaterial {
             material_index,
+            pipeline_category: phase.pipeline_category,
             texture: asset
                 .phase_textures
                 .get(phase_index)
@@ -1201,6 +1259,7 @@ fn append_environment_material(
         variants: vec![MaterialVariantSet {
             phase_material_indices,
             range_indices: Vec::new(),
+            pipeline_category: phases[0].pipeline_category,
         }],
         base: MaterialPhaseBinding {
             document,
@@ -1228,6 +1287,7 @@ fn append_environment_gradient_material(
     })?;
     materials.push(VulkanStaticMaterial {
         material_index,
+        pipeline_category: 0,
         texture: solid_environment_texture([255, 255, 255, 255]),
         directional_rgb: [1.0; 3],
         additive_rgb: [0.0; 3],
@@ -1275,6 +1335,7 @@ fn append_shadow_material(materials: &mut Vec<VulkanStaticMaterial>) -> Result<u
     let index = materials.len();
     materials.push(VulkanStaticMaterial {
         material_index,
+        pipeline_category: 0,
         texture: shadow_atlas_texture(),
         directional_rgb: [1.0; 3],
         additive_rgb: [0.0; 3],
@@ -1859,6 +1920,19 @@ fn screen_gradient_quad_vertices(
 }
 
 impl EnvironmentGpuScene {
+    fn transparent_background_range_indices(&self) -> Vec<usize> {
+        self.sky_layers
+            .iter()
+            .filter(|layer| {
+                matches!(
+                    layer.kind,
+                    SkyPassKind::NebulaStars | SkyPassKind::DomeGradient | SkyPassKind::Clouds
+                )
+            })
+            .map(|layer| layer.range.range_index)
+            .collect()
+    }
+
     fn fixed_range_indices(&self) -> HashSet<usize> {
         self.sky_layers
             .iter()
@@ -2289,9 +2363,9 @@ impl EnvironmentGpuScene {
                 && *index != cloud_index
         }));
         old_order.push(*shadow_range_index);
-        old_order.extend([nebula_index, dome_index]);
+        old_order.extend([nebula_index, dome_index, cloud_index]);
         old_order.extend(sprite_indices.iter().copied());
-        old_order.extend([cloud_index, rain_index, snow_index, lightning_index]);
+        old_order.extend([rain_index, snow_index, lightning_index]);
         let remap = reorder_draw_ranges(mesh, &old_order)?;
         for layer in &mut scene.sky_layers {
             layer.range.range_index = *remap
@@ -4165,6 +4239,7 @@ fn static_preview_terrain_base_materials(
                 })?;
                 materials.push(VulkanStaticMaterial {
                     material_index: preview_selector,
+                    pipeline_category: base_phase.pipeline_category,
                     texture: base.clone(),
                     detail_texture: Some(detail.clone()),
                     overlay_texture: overlay.map(|(texture, _)| texture.clone()),
@@ -4257,6 +4332,7 @@ fn static_preview_terrain_base_materials(
                 variants: vec![MaterialVariantSet {
                     phase_material_indices,
                     range_indices: Vec::new(),
+                    pipeline_category: base_phases[initial_phase_index].1.pipeline_category,
                 }],
                 base: MaterialPhaseBinding {
                     document: base_document,
@@ -4369,6 +4445,7 @@ fn static_preview_component_materials(
                 })?;
                 materials.push(VulkanStaticMaterial {
                     material_index: preview_selector,
+                    pipeline_category: material.pipeline_category,
                     texture,
                     detail_texture: None,
                     overlay_texture: None,
@@ -4405,6 +4482,7 @@ fn static_preview_component_materials(
                 variants: vec![MaterialVariantSet {
                     phase_material_indices,
                     range_indices: Vec::new(),
+                    pipeline_category: material.pipeline_category,
                 }],
                 base: MaterialPhaseBinding {
                     document: material.mat0.clone(),
@@ -4551,6 +4629,7 @@ fn append_static_preview_component_with_lightmaps(
                                 "static preview material selector {source_material_index} has no MAT0 animation binding"
                             )
                         })?;
+                let initial_phase_index = bindings[binding_index].initial_phase_index;
                 let lightmap = lightmap_textures
                     .get(usize::from(range.lightmap_index))
                     .expect("lightmap presence checked above");
@@ -4590,6 +4669,16 @@ fn append_static_preview_component_with_lightmaps(
                     materials.push(lightmap_material);
                     phase_material_indices.push(usize::from(index));
                 }
+                let initial_selector = phase_material_indices
+                    .get(initial_phase_index)
+                    .copied()
+                    .ok_or_else(|| "static preview lightmap phase table is empty".to_string())?;
+                let pipeline_category = materials
+                    .get(initial_selector)
+                    .map(|material| material.pipeline_category)
+                    .ok_or_else(|| {
+                        "static preview lightmap material selector is unavailable".to_string()
+                    })?;
                 let bindings = material_animations.as_deref_mut().ok_or_else(|| {
                     "static preview lightmap animation storage is unavailable".to_string()
                 })?;
@@ -4597,6 +4686,7 @@ fn append_static_preview_component_with_lightmaps(
                 bindings[binding_index].variants.push(MaterialVariantSet {
                     phase_material_indices: phase_material_indices.clone(),
                     range_indices: Vec::new(),
+                    pipeline_category,
                 });
                 let value = (phase_material_indices, binding_index, variant_index);
                 lightmap_materials.insert(key, value.clone());
@@ -4913,6 +5003,16 @@ impl StaticVulkanApp {
             renderer
                 .set_draw_range_transparency(range_index, transparent)
                 .map_err(|error| format!("configure world draw range {range_index}: {error}"))?;
+            let category = self
+                .materials
+                .get(usize::from(range.material_index))
+                .ok_or_else(|| "world draw range has no material selector".to_string())?
+                .pipeline_category;
+            renderer
+                .set_draw_range_material_category(range_index, category)
+                .map_err(|error| {
+                    format!("configure world material category {range_index}: {error}")
+                })?;
             renderer
                 .set_draw_range_index_count(
                     range_index,
@@ -5381,6 +5481,15 @@ impl ApplicationHandler for StaticVulkanApp {
             return;
         };
         let gpu_initialization_started = Instant::now();
+        if let Err(error) = configure_world_material_categories(
+            &mut self.mesh,
+            &self.materials,
+            &self.world_range_indices,
+        ) {
+            self.error = Some(error);
+            event_loop.exit();
+            return;
+        }
         let mut renderer = match VulkanSmokeRenderer::new(&VulkanSmokeRendererCreateInfo {
             application_name: "fparkan-game".to_string(),
             native_handles,
@@ -5399,6 +5508,15 @@ impl ApplicationHandler for StaticVulkanApp {
                 return;
             }
         };
+        let background_ranges = self.environment_gpu.as_ref().map_or_else(
+            Vec::new,
+            EnvironmentGpuScene::transparent_background_range_indices,
+        );
+        if let Err(error) = renderer.set_world_transparent_background_ranges(&background_ranges) {
+            self.error = Some(format!("configure world background ranges: {error}"));
+            event_loop.exit();
+            return;
+        }
         if let Err(error) = self.configure_world_draw_ranges(&mut renderer) {
             self.error = Some(error);
             event_loop.exit();
@@ -5975,6 +6093,7 @@ mod tests {
             variants: vec![MaterialVariantSet {
                 phase_material_indices: vec![10],
                 range_indices: vec![0, 2],
+                pipeline_category: 0,
             }],
             base: empty_binding(),
             detail: None,
@@ -6030,6 +6149,30 @@ mod tests {
     }
 
     #[test]
+    fn material_animation_selects_pipeline_category_with_active_phase() {
+        let variant = MaterialVariantSet {
+            phase_material_indices: vec![10, 11],
+            range_indices: vec![3],
+            pipeline_category: 1,
+        };
+        let category_for = |material_index| match material_index {
+            10 => Some(1),
+            11 => Some(2),
+            _ => None,
+        };
+
+        assert_eq!(
+            selected_material_phase(&variant, 0, category_for),
+            Ok((10, 1))
+        );
+        assert_eq!(
+            selected_material_phase(&variant, 1, category_for),
+            Ok((11, 2))
+        );
+        assert!(selected_material_phase(&variant, 2, category_for).is_err());
+    }
+
+    #[test]
     fn native_sun_object_source_types_map_to_world_kinds() {
         assert_eq!(native_shadow_kind(Some(PROTOTYPE_TYPE_FORT)), Some(3));
         assert_eq!(native_shadow_kind(Some(PROTOTYPE_TYPE_BTLU)), Some(4));
@@ -6187,6 +6330,7 @@ mod tests {
             variants: vec![MaterialVariantSet {
                 phase_material_indices: vec![10, 11],
                 range_indices: Vec::new(),
+                pipeline_category: 0,
             }],
             base: MaterialPhaseBinding {
                 document: empty_mat0,
@@ -6207,6 +6351,7 @@ mod tests {
         bindings[binding_index].variants.push(MaterialVariantSet {
             phase_material_indices: vec![20, 21],
             range_indices: vec![7],
+            pipeline_category: 0,
         });
 
         let lightmap_variant = &bindings[binding_index].variants[1];
diff --git a/docs/reference/materials.md b/docs/reference/materials.md
index bfeccf4..c148bc8 100644
--- a/docs/reference/materials.md
+++ b/docs/reference/materials.md
@@ -57,10 +57,12 @@ struct Phase34 {
 
 ### Pipeline category
 
-Call site извлекает native category как `(attr1 >> 2) & 0xF` и передаёт её в
-`LegacyPipelineState::with_material_category`. Таблица содержит пять
-подтверждённых категорий; helper возвращает `None` для остальных значений и не
-меняет уже выбранные depth и cull state.
+Call site извлекает native category как `(attr1 >> 2) & 0xF` и сохраняет её на
+разрешённом phase material. World draw ranges получают состояние для начального
+selector при подготовке, а animated selector обновляет category вместе с
+material selector. Fixed environment ranges keep their authored pipeline state.
+Таблица содержит пять подтверждённых категорий; helper возвращает `None` для
+остальных значений и не меняет уже выбранные depth и cull state.
 
 | category | source/destination colour factors | alpha test |
 | ---: | --- | --- |
@@ -75,6 +77,13 @@ material category. Alpha reference remains draw-range data, while the Vulkan
 pipeline key includes the blend mode, depth mode, cull mode and alpha-test
 variant so ranges with different native state do not share a pipeline.
 
+World transparency is a separate draw-queue decision. A world range joins that
+queue when sampled diffuse opacity is below one or any bit in the native
+`0x108` batch-flag mask is set; the MAT0 category alone does not make it
+transparent. A queued range
+with a depth attachment tests depth without writing it. Unsupported categories
+fail world-range setup instead of silently falling back to opaque state.
+
 Каждая phase занимает 34 байта: 18 parameter bytes и 16-byte C string имени
 текстуры. Loader переводит параметры в коэффициенты так:
 
diff --git a/docs/reference/render-frame.md b/docs/reference/render-frame.md
index 2c356dc..015f9f3 100644
--- a/docs/reference/render-frame.md
+++ b/docs/reference/render-frame.md
@@ -40,6 +40,47 @@ end-of-render.
 Подготовленный item должен ссылаться на immutable данные кадра. Изменение phase
 или texture cache посреди прохода не должно менять уже собранную очередь.
 
+## MAT0 state and transparent backgrounds
+
+For mission world ranges, the selected MAT0 material supplies its native
+pipeline category. The category sets blend and alpha-test state while preserving
+the range's depth and cull state; an animated material selector updates the
+category with the selector. Queue membership is independent: sampled opacity
+below one or native batch flags `0x108` mark a world range transparent, and a
+queued range with depth enabled tests depth without writing it. Fixed
+environment ranges keep their explicit states.
+
+The fixed-camera preview explicitly marks nebula/stars, dome and cloud ranges as
+transparent backgrounds. Opaque world ranges stay in their world slots; the
+transparent world queue is sorted back-to-front and inserted immediately after
+the last marked background. Other fixed ranges retain their relative order.
+Thus cloud layers can be drawn before transparent foliage, while later sun,
+weather and other foreground ranges keep their existing relative order. This
+is a narrow queue rule, not a reordering of every sky or effects pass.
+
+## Regression evidence
+
+`cargo test -p fparkan-render-vulkan --lib material_category_and_transparency_preserve_world_state_in_either_order --offline`
+checks that category 1 remains source-alpha with alpha testing, retains depth
+and cull settings in either update order, and rejects unsupported categories.
+`cargo test -p fparkan-render-vulkan --lib tree_canopy_queue_follows_sky_and_precedes_foreground_effects --offline`
+checks the explicit queue order: screen gradient, opaque terrain/building,
+shadow, nebula/dome/clouds, far-to-near transparent canopy, then sun/weather.
+
+Viewer-only paired readbacks used `--frames 3 --validation
+--legacy-camera-capture` with the pre-fix and patched builds. On AutoDemo TMA
+object 4 (`wor_l_n1.dat`, `fr_l_plant`), the 1280x720 camera at eye
+`[464.319, 904.719, 38.0]`, aimed at `[374.319, 814.719, 12.0]` with FOV
+`0.62`, changed the two black facade panels to tinted, textured portal
+surfaces. On Mission.01 object 12 (`s_tree_04`), the 1280x1024 camera at eye
+`[492.63855, 312.90244, 46.5]` aimed at
+`[492.63855, 442.90244, 55.0]` crosses the canopy against open sky; paired
+three-frame captures at the same synthetic atmosphere phase (600 seconds) show
+the patched build restoring the missing upper/right fronds along that sky
+boundary. Both runs reported clean Vulkan validation. These captures verify our
+preview behavior and do not prove the native renderer's pass order, portal
+transmittance or exact color.
+
 ## GOG camera dispatch evidence
 
 For the GOG `World3D.dll` baseline with SHA-256
diff --git a/docs/tomes/06-behavior.md b/docs/tomes/06-behavior.md
index a3fa711..8b5b09f 100644
--- a/docs/tomes/06-behavior.md
+++ b/docs/tomes/06-behavior.md
@@ -275,14 +275,17 @@ buffers и передаёт собранную settings-структуру да�
 `ret 0x0c`; `CreateCollManager` и `CreateCollObject` возвращают interface
 pointer с поправкой `+4` после внутренней инициализации.
 
-Headless Ghidra 12.1.2 decompile GOG binary подтверждает ABI формой экспортов
-`LoadControlSystem(char*, char*, char*, char*, char*, u32, void*, i32)`,
+Инструкциям x86 в GOG `Control.dll` (`+0x32280`) и caller-у в `AniMesh.dll`
+(`+0x32e7`) соответствует ABI `LoadControlSystem(char*, char*, char*, char*,
+char*, char*, void*, i32)`: шесть C-string pointers, resource context и mode.
+Функция заканчивается `ret 0x20`, то есть снимает все восемь 32-bit stack
+arguments; arg7 передаётся constructor-у как context, arg8 выбирает mode.
+Прежняя декомпиляция ошибочно определяла шестой строковый аргумент как `u32`.
+Остальные exports имеют формы
 `LoadPhysicalModel(u32, u32, u32)`, `CreateCollManager(u32)` и
-`CreateCollObject(u32, u32)`. Первые пять параметров Control loader — строки,
-а mode передаётся последним; decompiler не восстанавливает предметные имена
-остальных слов. `InitializeSettings` получает `CreateGameSettings()` из
-World3D и делает virtual call slot `+0x24` с literal `0x15` и строкой по RVA
-`0x42478`.
+`CreateCollObject(u32, u32)`. `InitializeSettings` получает
+`CreateGameSettings()` из World3D и делает virtual call slot `+0x24` с literal
+`0x15` и строкой по RVA `0x42478`.
 
 Именно update methods этих private objects, а не пять exports, остаются
 следующим объектом динамической трассировки. Поэтому reference movement в