[rmodels] UpdateModelAnimation(), compute bone normal matrices once per bone instead of per vertex (#6191)

* [rmodels] `UpdateModelAnimation()`, compute bone normal matrices once per bone instead of per vertex

* [rmodels] use a static buffer for bone normal matrices

examples/shaders/shaders_mesh_instancing.c

@@ -139,6 +139,9 @@ int main(void)
     // De-Initialization
     //--------------------------------------------------------------------------------------
     RL_FREE(transforms);    // Free transforms
+    UnloadMaterial(matInstances);    // Also unloads the instancing shader
+    UnloadMaterial(matDefault);      // Unload default material
+    UnloadMesh(cube);                // Unload cube mesh
 
     CloseWindow();          // Close window and OpenGL context
     //--------------------------------------------------------------------------------------

src/external/vox_loader.h

@@ -733,6 +733,7 @@ void Vox_FreeArrays(VoxArray3D* voxarray)
 
 	// Free arrays
 	freeArrayVector3(&voxarray->vertices);
+	freeArrayVector3(&voxarray->normals);
 	freeArrayUShort(&voxarray->indices);
 	freeArrayColor(&voxarray->colors);
 }

src/platforms/rcore_desktop_win32.c

@@ -2000,7 +2000,7 @@ static LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lpara
                 EndPaint(hwnd, &ps);
             }
             else DefWindowProc(hwnd, msg, wparam, lparam);
-        }
+        } break;
         case WM_INPUT:
         {
             //HandleRawInput(lparam);

src/rmodels.c

@@ -2486,6 +2486,9 @@ void UpdateModelAnimationEx(Model model, ModelAnimation animA, float frameA, Mod
 // NOTE: Required for CPU skinning, uploads animated vertex buffers to GPU
 static void UpdateModelAnimationVertexBuffers(Model model)
 {
+    static Matrix boneNormalMatrices[256] = { 0 }; // Normal matrix per bone, bone indices are unsigned char
+    bool boneNormalsReady = false;
+
     for (int m = 0; m < model.meshCount; m++)
     {
         Mesh mesh = model.meshes[m];
@@ -2502,6 +2505,14 @@ static void UpdateModelAnimationVertexBuffers(Model model)
         if ((mesh.boneWeights == NULL) || (mesh.boneIndices == NULL) ||
             (mesh.animVertices == NULL) || (mesh.animNormals == NULL)) continue;
 
+        // Normal matrix only depends on the bone, compute it once per bone instead of per vertex
+        if ((mesh.normals != NULL) && !boneNormalsReady)
+        {
+            memset(boneNormalMatrices, 0, 256*sizeof(Matrix));
+            for (unsigned int b = 0; (b < model.skeleton.boneCount) && (b < 256); b++) boneNormalMatrices[b] = MatrixTranspose(MatrixInvert(model.boneMatrices[b]));
+            boneNormalsReady = true;
+        }
+
         for (int vCounter = 0; vCounter < vertexValuesCount; vCounter += 3)
         {
             mesh.animVertices[vCounter] = 0;
@@ -2534,7 +2545,7 @@ static void UpdateModelAnimationVertexBuffers(Model model)
                 if ((mesh.normals != NULL) && (mesh.animNormals != NULL ))
                 {
                     animNormal = (Vector3){ mesh.normals[vCounter], mesh.normals[vCounter + 1], mesh.normals[vCounter + 2] };
-                    animNormal = Vector3Transform(animNormal, MatrixTranspose(MatrixInvert(model.boneMatrices[boneIndex])));
+                    animNormal = Vector3Transform(animNormal, boneNormalMatrices[boneIndex]);
                     mesh.animNormals[vCounter] += animNormal.x*boneWeight;
                     mesh.animNormals[vCounter + 1] += animNormal.y*boneWeight;
                     mesh.animNormals[vCounter + 2] += animNormal.z*boneWeight;