TextureTransform: set material transform only when the extension is provided.

code/glTF2/glTF2Asset.h

@@ -685,10 +685,13 @@ namespace glTF2
         Ref<Texture> texture;
         unsigned int index;
         unsigned int texCoord = 0;
-        
-        float offset[2];
-		float rotation;
-		float scale[2];
+
+        bool textureTransformSupported = false;
+        struct TextureTransformExt {
+			float offset[2];
+			float rotation;
+			float scale[2];
+		} TextureTransformExt_t;
     };
 
     struct NormalTextureInfo : TextureInfo

code/glTF2/glTF2Asset.inl

@@ -803,25 +803,26 @@ namespace {
     inline void SetTextureProperties(Asset& r, Value* prop, TextureInfo& out) {
 	    if (r.extensionsUsed.KHR_texture_transform) {
             if (Value *extensions = FindObject(*prop, "extensions")) {
-				if (Value *pKHR_texture_transform = FindObject(*extensions, "KHR_texture_transform")) {
+				out.textureTransformSupported = true;
+                if (Value *pKHR_texture_transform = FindObject(*extensions, "KHR_texture_transform")) {
 					if (Value *array = FindArray(*pKHR_texture_transform, "offset")) {
-						out.offset[0] = (*array)[0].GetFloat();
-						out.offset[1] = (*array)[1].GetFloat();
+						out.TextureTransformExt_t.offset[0] = (*array)[0].GetFloat();
+						out.TextureTransformExt_t.offset[1] = (*array)[1].GetFloat();
 					} else {
-						out.offset[0] = 0;
-						out.offset[1] = 0;
+						out.TextureTransformExt_t.offset[0] = 0;
+						out.TextureTransformExt_t.offset[1] = 0;
 					}      
 					
-                    if (!ReadMember(*pKHR_texture_transform, "rotation", out.rotation)) {
-						out.rotation = 0;					
+                    if (!ReadMember(*pKHR_texture_transform, "rotation", out.TextureTransformExt_t.rotation)) {
+						out.TextureTransformExt_t.rotation = 0;					
                     }
 					
                     if (Value *array = FindArray(*pKHR_texture_transform, "scale")) {
-						out.scale[0] = (*array)[0].GetFloat();
-						out.scale[1] = (*array)[1].GetFloat();
+						out.TextureTransformExt_t.scale[0] = (*array)[0].GetFloat();
+						out.TextureTransformExt_t.scale[1] = (*array)[1].GetFloat();
 					} else {
-						out.scale[0] = 1;
-						out.scale[1] = 1;
+						out.TextureTransformExt_t.scale[0] = 1;
+						out.TextureTransformExt_t.scale[1] = 1;
                     }
 				}
 			}