Propertly transform UV coordinates.

We were mapping v to -v rather than 1-v, with fairly catastrophic
results. While fixing, take the trouble to introduce a more general
transformation mechanism than just an affine matrix.

src/RawModel.cpp

@@ -336,14 +336,18 @@ void RawModel::Condense()
     }
 }
 
-void RawModel::TransformTextures(const Mat2f &transform)
+void RawModel::TransformTextures(const std::vector<std::function<Vec2f(Vec2f)>> &transforms)
 {
-    for (size_t i = 0; i < vertices.size(); i++) {
+    for (auto &vertice : vertices) {
         if ((vertexAttributes & RAW_VERTEX_ATTRIBUTE_UV0) != 0) {
-            vertices[i].uv0 = transform * vertices[i].uv0;
+            for (const auto &fun : transforms) {
+                vertice.uv0 = fun(vertice.uv0);
+            }
         }
         if ((vertexAttributes & RAW_VERTEX_ATTRIBUTE_UV1) != 0) {
-            vertices[i].uv1 = transform * vertices[i].uv1;
+            for (const auto &fun : transforms) {
+                vertice.uv1 = fun(vertice.uv1);
+            }
         }
     }
 }

src/RawModel.h

@@ -255,7 +255,7 @@ public:
     // Remove unused vertices, textures or materials after removing vertex attributes, textures, materials or surfaces.
     void Condense();
 
-    void TransformTextures(const Mat2f &transform);
+    void TransformTextures(const std::vector<std::function<Vec2f(Vec2f)>> &transforms);
 
     // Get the attributes stored per vertex.
     int GetVertexAttributes() const { return vertexAttributes; }

src/main.cpp

@@ -40,8 +40,7 @@ int main(int argc, char *argv[])
     std::string inputPath;
     std::string outputPath;
 
-    Mat2f texturesTransform(0.0f);
-    bool  doTransformTextures = false;
+    std::vector<std::function<Vec2f(Vec2f)>> texturesTransforms;
 
     GltfOptions gltfOptions{
         -1,            // keepAttribs
@@ -123,20 +122,16 @@ Copyright (c) 2016-2017 Oculus VR, LLC.
 
     if (!gltfOptions.useKHRMatCom && !gltfOptions.usePBRSpecGloss && !gltfOptions.usePBRMetRough) {
         if (verboseOutput) {
-            fmt::printf("Defaulting to KHR_materials_common material support.\n");
+            fmt::printf("Defaulting to --pbr-metallic-roughness material support.\n");
         }
-        gltfOptions.useKHRMatCom = true;
+        gltfOptions.usePBRMetRough = true;
     }
 
     if (options.count("flip-u") > 0) {
-        texturesTransform(0, 0) = -1.0f;
-        texturesTransform(1, 1) =  1.0f;
-        doTransformTextures = true;
+        texturesTransforms.emplace_back([](Vec2f uv) { return Vec2f(1.0f - uv[0], uv[1]); });
     }
     if (options.count("flip-v") > 0) {
-        texturesTransform(0, 0) =  1.0f;
-        texturesTransform(1, 1) = -1.0f;
-        doTransformTextures = true;
+        texturesTransforms.emplace_back([](Vec2f uv) { return Vec2f(uv[0], 1.0f - uv[1]); });
     }
 
     if (options.count("keepAttribute")) {
@@ -192,8 +187,8 @@ Copyright (c) 2016-2017 Oculus VR, LLC.
         return 1;
     }
 
-    if (doTransformTextures) {
-        raw.TransformTextures(texturesTransform);
+    if (!texturesTransforms.empty()) {
+        raw.TransformTextures(texturesTransforms);
     }
     raw.Condense();