Add capybara

destrum/assets_src/shaders/skinning.comp

@@ -10,12 +10,14 @@ struct SkinningDataType {
     vec4 weights;
 };
 
-layout (buffer_reference, std430) readonly buffer SkinningData {
-	SkinningDataType data[];
+// Keep buffer-reference pointer alignment explicit so the C++ push-constant
+// struct can safely use 64-bit VkDeviceAddress fields.
+layout (buffer_reference, std430, buffer_reference_align = 8) readonly buffer SkinningData {
+    SkinningDataType data[];
 };
 
-layout (buffer_reference, std430) readonly buffer JointMatrices {
-	mat4 matrices[];
+layout (buffer_reference, std430, buffer_reference_align = 8) readonly buffer JointMatrices {
+    mat4 matrices[];
 };
 
 layout (push_constant) uniform constants
@@ -23,16 +25,45 @@ layout (push_constant) uniform constants
     JointMatrices jointMatrices;
     uint jointMatricesStartIndex;
     uint numVertices;
-	VertexBuffer inputBuffer;
+    VertexBuffer inputBuffer;
     SkinningData skinningData;
-	VertexBuffer outputBuffer;
+    VertexBuffer outputBuffer;
 } pcs;
 
 layout (local_size_x = 256, local_size_y = 1, local_size_z = 1) in;
 
 mat4 getJointMatrix(int jointId) {
-    if (jointId < 0) return mat4(1.0);
-    return pcs.jointMatrices.matrices[pcs.jointMatricesStartIndex + jointId];
+    if (jointId < 0) {
+        return mat4(1.0);
+    }
+
+    return pcs.jointMatrices.matrices[pcs.jointMatricesStartIndex + uint(jointId)];
+}
+
+vec3 safeNormalize(vec3 v, vec3 fallback) {
+    float len2 = dot(v, v);
+    if (len2 <= 1e-20) {
+        return fallback;
+    }
+    return v * inversesqrt(len2);
+}
+
+mat4 buildSkinMatrix(SkinningDataType sd) {
+    // If imported weights are slightly imperfect, normalize them here as a
+    // second line of defense. If a vertex has no weights at all, pass it
+    // through unchanged instead of collapsing it to vec3(0).
+    float weightSum = sd.weights.x + sd.weights.y + sd.weights.z + sd.weights.w;
+    if (weightSum <= 1e-8) {
+        return mat4(1.0);
+    }
+
+    vec4 w = sd.weights / weightSum;
+
+    return
+        w.x * getJointMatrix(sd.jointIds.x) +
+        w.y * getJointMatrix(sd.jointIds.y) +
+        w.z * getJointMatrix(sd.jointIds.z) +
+        w.w * getJointMatrix(sd.jointIds.w);
 }
 
 void main()
@@ -42,19 +73,18 @@ void main()
         return;
     }
 
-    SkinningDataType sd = pcs.skinningData.data[index];
-    mat4 skinMatrix =
-        sd.weights.x * getJointMatrix(sd.jointIds.x) +
-        sd.weights.y * getJointMatrix(sd.jointIds.y) +
-        sd.weights.z * getJointMatrix(sd.jointIds.z) +
-        sd.weights.w * getJointMatrix(sd.jointIds.w);
-
     Vertex v = pcs.inputBuffer.vertices[index];
+    SkinningDataType sd = pcs.skinningData.data[index];
+    mat4 skinMatrix = buildSkinMatrix(sd);
+
     v.position = vec3(skinMatrix * vec4(v.position, 1.0));
 
+    // For rigid joint matrices this is correct. If you allow non-uniform scale
+    // in bones, replace this with a proper inverse-transpose normal matrix path.
     mat3 skinMat3 = mat3(skinMatrix);
-    v.normal = skinMat3 * v.normal;
-    v.tangent.xyz = skinMat3 * v.tangent.xyz; // don't transform tangent.w
+    v.normal = safeNormalize(skinMat3 * v.normal, v.normal);
+    v.tangent.xyz = safeNormalize(skinMat3 * v.tangent.xyz, v.tangent.xyz);
+    // v.tangent.w is handedness; do not transform it.
 
     pcs.outputBuffer.vertices[index] = v;
 }