wmo: apply MOHD ambient color to interior group lighting

Read the ambient color from the MOHD chunk (BGRA uint32) and store it
on WMOModel as a normalized RGB vec3.  Pass it through ModelData into
the per-batch WMOMaterialUBO (replacing the unused pad[3] bytes, keeping
the struct at 64 bytes).  The GLSL interior branch now floors vertex
colors against the WMO ambient instead of a hardcoded 0.5, so dungeon
interiors respect the artist-specified ambient tint from the WMO root
rather than always clamping to grey.

assets/shaders/wmo.frag.glsl

@@ -29,6 +29,9 @@ layout(set = 1, binding = 1) uniform WMOMaterial {
     float heightMapVariance;
     float normalMapStrength;
     int isLava;
+    float wmoAmbientR;
+    float wmoAmbientG;
+    float wmoAmbientB;
 };
 
 layout(set = 1, binding = 2) uniform sampler2D uNormalHeightMap;
@@ -185,7 +188,13 @@ void main() {
     } else if (unlit != 0) {
         result = texColor.rgb * shadow;
     } else if (isInterior != 0) {
-        vec3 mocv = max(VertColor.rgb, vec3(0.5));
+        // WMO interior: vertex colors (MOCV) are pre-baked lighting from the artist.
+        // The MOHD ambient color tints/floors the vertex colors so dark spots don't
+        // go completely black, matching the WoW client's interior shading.
+        vec3 wmoAmbient = vec3(wmoAmbientR, wmoAmbientG, wmoAmbientB);
+        // Clamp ambient to at least 0.3 to avoid total darkness when MOHD color is zero
+        wmoAmbient = max(wmoAmbient, vec3(0.3));
+        vec3 mocv = max(VertColor.rgb, wmoAmbient);
         result = texColor.rgb * mocv * shadow;
     } else {
         vec3 ldir = normalize(-lightDir.xyz);

include/pipeline/wmo_loader.hpp

@@ -185,6 +185,7 @@ struct WMOModel {
     uint32_t nDoodadDefs;
     uint32_t nDoodadSets;
 
+    glm::vec3 ambientColor;     // MOHD ambient color (used for interior group lighting)
     glm::vec3 boundingBoxMin;
     glm::vec3 boundingBoxMax;
 

include/rendering/wmo_renderer.hpp

@@ -353,7 +353,9 @@ private:
         float heightMapVariance;   // 40 (low variance = skip POM)
         float normalMapStrength;   // 44 (0=flat, 1=full, 2=exaggerated)
         int32_t isLava;            // 48 (1=lava/magma UV scroll)
-        float pad[3];              // 52-60 padding to 64 bytes
+        float wmoAmbientR;         // 52 (interior ambient color R)
+        float wmoAmbientG;         // 56 (interior ambient color G)
+        float wmoAmbientB;         // 60 (interior ambient color B)
     };  // 64 bytes total
 
     /**
@@ -472,6 +474,7 @@ private:
         std::vector<GroupResources> groups;
         glm::vec3 boundingBoxMin;
         glm::vec3 boundingBoxMax;
+        glm::vec3 wmoAmbientColor{0.5f, 0.5f, 0.5f};  // From MOHD, used for interior lighting
         bool isLowPlatform = false;
 
         // Doodad templates (M2 models placed in WMO, stored for instancing)

src/pipeline/wmo_loader.cpp

@@ -109,7 +109,11 @@ WMOModel WMOLoader::load(const std::vector<uint8_t>& wmoData) {
                 model.nDoodadDefs = read<uint32_t>(wmoData, offset);
                 model.nDoodadSets = read<uint32_t>(wmoData, offset);
 
-                [[maybe_unused]] uint32_t ambColor = read<uint32_t>(wmoData, offset);  // Ambient color (BGRA)
+                uint32_t ambColor = read<uint32_t>(wmoData, offset);  // Ambient color (BGRA)
+                // Unpack BGRA bytes to normalized [0,1] RGB
+                model.ambientColor.r = ((ambColor >> 16) & 0xFF) / 255.0f;
+                model.ambientColor.g = ((ambColor >>  8) & 0xFF) / 255.0f;
+                model.ambientColor.b = ((ambColor >>  0) & 0xFF) / 255.0f;
                 [[maybe_unused]] uint32_t wmoID = read<uint32_t>(wmoData, offset);
 
                 model.boundingBoxMin.x = read<float>(wmoData, offset);

src/rendering/wmo_renderer.cpp

@@ -414,6 +414,7 @@ bool WMORenderer::loadModel(const pipeline::WMOModel& model, uint32_t id) {
     modelData.id = id;
     modelData.boundingBoxMin = model.boundingBoxMin;
     modelData.boundingBoxMax = model.boundingBoxMax;
+    modelData.wmoAmbientColor = model.ambientColor;
     {
         glm::vec3 ext = model.boundingBoxMax - model.boundingBoxMin;
         float horiz = std::max(ext.x, ext.y);
@@ -681,6 +682,9 @@ bool WMORenderer::loadModel(const pipeline::WMOModel& model, uint32_t id) {
             matData.heightMapVariance = mb.heightMapVariance;
             matData.normalMapStrength = normalMapStrength_;
             matData.isLava = mb.isLava ? 1 : 0;
+            matData.wmoAmbientR = modelData.wmoAmbientColor.r;
+            matData.wmoAmbientG = modelData.wmoAmbientColor.g;
+            matData.wmoAmbientB = modelData.wmoAmbientColor.b;
             if (matBuf.info.pMappedData) {
                 memcpy(matBuf.info.pMappedData, &matData, sizeof(matData));
             }