From 575124830b678d0c4d5b37a708bba9692a4e47ef Mon Sep 17 00:00:00 2001
From: Valentin Popov <valentin@popov.link>
Date: Sat, 18 Jul 2026 17:31:13 +0400
Subject: feat(terrain): separate shade material selections

---
 crates/fparkan-terrain-format/src/lib.rs | 23 +++++++++++++++++++++++
 crates/fparkan-terrain/src/lib.rs        |  4 +++-
 2 files changed, 26 insertions(+), 1 deletion(-)

(limited to 'crates')

diff --git a/crates/fparkan-terrain-format/src/lib.rs b/crates/fparkan-terrain-format/src/lib.rs
index ce97d62..764de09 100644
--- a/crates/fparkan-terrain-format/src/lib.rs
+++ b/crates/fparkan-terrain-format/src/lib.rs
@@ -211,6 +211,22 @@ pub struct TerrainMaterialPair {
     pub flags: u16,
 }
 
+impl TerrainMaterialPair {
+    /// Returns the material-manager selection used by `GetShade`.
+    ///
+    /// `GetShade` owns a manager loaded only with `Shade.wea`, so its
+    /// 16-bit lookup occupies row bits of that manager's table zero. It is
+    /// deliberately separate from the `Land1.wea`/`Land2.wea` selections
+    /// carried by [`TerrainMaterialLayers`].
+    #[must_use]
+    pub const fn shade_selection(self) -> TerrainMaterialSelection {
+        TerrainMaterialSelection {
+            table_index: 0,
+            material_index: self.material_lookup,
+        }
+    }
+}
+
 impl TerrainSlotTable {
     /// Returns the render-dispatch header for one decoded slot record.
     #[must_use]
@@ -1569,6 +1585,13 @@ mod tests {
                 },
             ])
         );
+        assert_eq!(
+            document.slot_material_pairs(0).expect("material pairs")[0].shade_selection(),
+            TerrainMaterialSelection {
+                table_index: 0,
+                material_index: 0x0102,
+            }
+        );
         assert_eq!(document.slot_material_pairs(1), None);
 
         document.slots.slots_raw[0][2..4].copy_from_slice(&3_u16.to_le_bytes());
diff --git a/crates/fparkan-terrain/src/lib.rs b/crates/fparkan-terrain/src/lib.rs
index 4eef871..a69df2a 100644
--- a/crates/fparkan-terrain/src/lib.rs
+++ b/crates/fparkan-terrain/src/lib.rs
@@ -27,7 +27,9 @@ use std::collections::VecDeque;
 ///
 /// Applications access this semantic terrain API through this terrain crate
 /// rather than taking a direct dependency on the binary-format parser.
-pub use fparkan_terrain_format::{TerrainMaterialLayers, TerrainMaterialSelection};
+pub use fparkan_terrain_format::{
+    TerrainMaterialLayers, TerrainMaterialPair, TerrainMaterialSelection,
+};
 
 /// Terrain world.
 #[derive(Clone, Debug, Default)]
-- 
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