Diffuse color and diffuse texture import and export improvements

These changes do a better of importing and exporting baseColor colors and textures, as well as diffuse colors and textures (in the case of pbrSpecularGlossiness)

- baseColorFactor will be stored on both `$clr.diffuse` and `$mat.gltf.pbrMetallicRoughness.baseColorFactor`, and will be extracted from `$mat.gltf.pbrMetallicRoughness.baseColorFactor` first, and falling back to `$clr.diffuse`. The behaviour for baseColorTexture is similar
- pbrSG’s diffuseFactor will now only be store on `$clr.diffuse` (overwriting any previous assignments to `$clr.diffuse`, e.g. from metallicRoughness’ baseColorFactor, as diffuseFactor is more analogous to diffuse color than baseColor), and will only extract from `$clr.diffuse`

code/glTF2Asset.h

@@ -164,16 +164,16 @@ namespace glTF2
     //! Magic number for GLB files
 	#define AI_GLB_MAGIC_NUMBER "glTF"
 
+    #define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_BASE_COLOR_FACTOR "$mat.gltf.pbrMetallicRoughness.baseColorFactor", 0, 0
 	#define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_METALLIC_FACTOR "$mat.gltf.pbrMetallicRoughness.metallicFactor", 0, 0
 	#define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_ROUGHNESS_FACTOR "$mat.gltf.pbrMetallicRoughness.roughnessFactor", 0, 0
+    #define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_BASE_COLOR_TEXTURE aiTextureType_DIFFUSE, 1
 	#define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_METALLICROUGHNESS_TEXTURE aiTextureType_UNKNOWN, 0
 	#define AI_MATKEY_GLTF_ALPHAMODE "$mat.gltf.alphaMode", 0, 0
 	#define AI_MATKEY_GLTF_ALPHACUTOFF "$mat.gltf.alphaCutoff", 0, 0
 	#define AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS "$mat.gltf.pbrSpecularGlossiness", 0, 0
-	#define AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_DIFFUSE_FACTOR "$clr.diffuse", 0, 1
 	#define AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_SPECULAR_FACTOR "$clr.specular", 0, 1
 	#define AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_GLOSSINESS_FACTOR "$mat.gltf.pbrMetallicRoughness.glossinessFactor", 0, 0
-	#define AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_DIFFUSE_TEXTURE aiTextureType_DIFFUSE, 1
 	#define AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_SPECULARGLOSSINESS_TEXTURE aiTextureType_UNKNOWN, 1
 
 	#define _AI_MATKEY_GLTF_TEXTURE_TEXCOORD_BASE "$tex.file.texCoord"

code/glTF2Exporter.cpp

@@ -372,20 +372,28 @@ void glTF2Exporter::GetMatTex(const aiMaterial* mat, OcclusionTextureInfo& prop,
     }
 }
 
-void glTF2Exporter::GetMatColor(const aiMaterial* mat, vec4& prop, const char* propName, int type, int idx)
+aiReturn glTF2Exporter::GetMatColor(const aiMaterial* mat, vec4& prop, const char* propName, int type, int idx)
 {
     aiColor4D col;
-    if (mat->Get(propName, type, idx, col) == AI_SUCCESS) {
+    aiReturn result = mat->Get(propName, type, idx, col);
+
+    if (result == AI_SUCCESS) {
         prop[0] = col.r; prop[1] = col.g; prop[2] = col.b; prop[3] = col.a;
     }
+
+    return result;
 }
 
-void glTF2Exporter::GetMatColor(const aiMaterial* mat, vec3& prop, const char* propName, int type, int idx)
+aiReturn glTF2Exporter::GetMatColor(const aiMaterial* mat, vec3& prop, const char* propName, int type, int idx)
 {
     aiColor3D col;
-    if (mat->Get(propName, type, idx, col) == AI_SUCCESS) {
+    aiReturn result = mat->Get(propName, type, idx, col);
+
+    if (result == AI_SUCCESS) {
         prop[0] = col.r; prop[1] = col.g; prop[2] = col.b;
     }
+
+    return result;
 }
 
 void glTF2Exporter::ExportMaterials()
@@ -406,9 +414,20 @@ void glTF2Exporter::ExportMaterials()
 
         m->name = name;
 
-        GetMatTex(mat, m->pbrMetallicRoughness.baseColorTexture, aiTextureType_DIFFUSE);
+        GetMatTex(mat, m->pbrMetallicRoughness.baseColorTexture, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_BASE_COLOR_TEXTURE);
+
+        if (!m->pbrMetallicRoughness.baseColorTexture.texture) {
+            //if there wasn't a baseColorTexture defined in the source, fallback to any diffuse texture
+            GetMatTex(mat, m->pbrMetallicRoughness.baseColorTexture, aiTextureType_DIFFUSE);
+        }
+
         GetMatTex(mat, m->pbrMetallicRoughness.metallicRoughnessTexture, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_METALLICROUGHNESS_TEXTURE);
-        GetMatColor(mat, m->pbrMetallicRoughness.baseColorFactor, AI_MATKEY_COLOR_DIFFUSE);
+
+        if (GetMatColor(mat, m->pbrMetallicRoughness.baseColorFactor, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_BASE_COLOR_FACTOR) != AI_SUCCESS) {
+            // if baseColorFactor wasn't defined, then the source is likely not a metallic roughness material.
+            //a fallback to any diffuse color should be used instead
+            GetMatColor(mat, m->pbrMetallicRoughness.baseColorFactor, AI_MATKEY_COLOR_DIFFUSE);
+        }
 
         if (mat->Get(AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_METALLIC_FACTOR, m->pbrMetallicRoughness.metallicFactor) != AI_SUCCESS) {
             //if metallicFactor wasn't defined, then the source is likely not a PBR file, and the metallicFactor should be 0
@@ -451,11 +470,11 @@ void glTF2Exporter::ExportMaterials()
 
             PbrSpecularGlossiness pbrSG;
 
-            GetMatColor(mat, pbrSG.diffuseFactor, AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_DIFFUSE_FACTOR);
             GetMatColor(mat, pbrSG.specularFactor, AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_SPECULAR_FACTOR);
             mat->Get(AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_GLOSSINESS_FACTOR, pbrSG.glossinessFactor);
-            GetMatTex(mat, pbrSG.diffuseTexture, AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_DIFFUSE_TEXTURE);
             GetMatTex(mat, pbrSG.specularGlossinessTexture, AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_SPECULARGLOSSINESS_TEXTURE);
+            GetMatColor(mat, pbrSG.diffuseFactor, AI_MATKEY_COLOR_DIFFUSE);
+            GetMatTex(mat, pbrSG.diffuseTexture, aiTextureType_DIFFUSE);
 
             m->pbrSpecularGlossiness = Nullable<PbrSpecularGlossiness>(pbrSG);
         }

code/glTF2Exporter.h

@@ -115,8 +115,8 @@ namespace Assimp
         void GetMatTex(const aiMaterial* mat, glTF2::TextureInfo& prop, aiTextureType tt, unsigned int slot);
         void GetMatTex(const aiMaterial* mat, glTF2::NormalTextureInfo& prop, aiTextureType tt, unsigned int slot);
         void GetMatTex(const aiMaterial* mat, glTF2::OcclusionTextureInfo& prop, aiTextureType tt, unsigned int slot);
-        void GetMatColor(const aiMaterial* mat, glTF2::vec4& prop, const char* propName, int type, int idx);
+        aiReturn GetMatColor(const aiMaterial* mat, glTF2::vec4& prop, const char* propName, int type, int idx);
-        void GetMatColor(const aiMaterial* mat, glTF2::vec3& prop, const char* propName, int type, int idx);
+        aiReturn GetMatColor(const aiMaterial* mat, glTF2::vec3& prop, const char* propName, int type, int idx);
         void ExportMetadata();
         void ExportMaterials();
         void ExportMeshes();

code/glTF2Importer.cpp

@@ -228,7 +228,11 @@ void glTF2Importer::ImportMaterials(glTF2::Asset& r)
         }
 
         SetMaterialColorProperty(r, mat.pbrMetallicRoughness.baseColorFactor, aimat, AI_MATKEY_COLOR_DIFFUSE);
+        SetMaterialColorProperty(r, mat.pbrMetallicRoughness.baseColorFactor, aimat, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_BASE_COLOR_FACTOR);
+
         SetMaterialTextureProperty(embeddedTexIdxs, r, mat.pbrMetallicRoughness.baseColorTexture, aimat, aiTextureType_DIFFUSE);
+        SetMaterialTextureProperty(embeddedTexIdxs, r, mat.pbrMetallicRoughness.baseColorTexture, aimat, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_BASE_COLOR_TEXTURE);
+
         SetMaterialTextureProperty(embeddedTexIdxs, r, mat.pbrMetallicRoughness.metallicRoughnessTexture, aimat, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_METALLICROUGHNESS_TEXTURE);
         aimat->AddProperty(&mat.pbrMetallicRoughness.metallicFactor, 1, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_METALLIC_FACTOR);
         aimat->AddProperty(&mat.pbrMetallicRoughness.roughnessFactor, 1, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_ROUGHNESS_FACTOR);
@@ -249,11 +253,11 @@ void glTF2Importer::ImportMaterials(glTF2::Asset& r)
             PbrSpecularGlossiness &pbrSG = mat.pbrSpecularGlossiness.value;
 
             aimat->AddProperty(&mat.pbrSpecularGlossiness.isPresent, 1, AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS);
-            SetMaterialColorProperty(r, pbrSG.diffuseFactor, aimat, AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_DIFFUSE_FACTOR);
             SetMaterialColorProperty(r, pbrSG.specularFactor, aimat, AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_SPECULAR_FACTOR);
+            SetMaterialColorProperty(r, pbrSG.diffuseFactor, aimat, AI_MATKEY_COLOR_DIFFUSE);
             aimat->AddProperty(&pbrSG.glossinessFactor, 1, AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_GLOSSINESS_FACTOR);
-            SetMaterialTextureProperty(embeddedTexIdxs, r, pbrSG.diffuseTexture, aimat, AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_DIFFUSE_TEXTURE);
             SetMaterialTextureProperty(embeddedTexIdxs, r, pbrSG.specularGlossinessTexture, aimat, AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_SPECULARGLOSSINESS_TEXTURE);
+            SetMaterialTextureProperty(embeddedTexIdxs, r, pbrSG.diffuseTexture, aimat, aiTextureType_DIFFUSE);
         }
     }
 }