First pass at simplifying glTFv2 PBR

Removed 'core' set of GLTF-specific properties

code/AssetLib/glTF2/glTF2Exporter.cpp

@@ -645,7 +645,7 @@ void glTF2Exporter::ExportMaterials()
 
         m->name = name;
 
-        GetMatTex(mat, m->pbrMetallicRoughness.baseColorTexture, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_BASE_COLOR_TEXTURE);
+        GetMatTex(mat, m->pbrMetallicRoughness.baseColorTexture, aiTextureType_BASE_COLOR);
 
         if (!m->pbrMetallicRoughness.baseColorTexture.texture) {
             //if there wasn't a baseColorTexture defined in the source, fallback to any diffuse texture
@@ -654,19 +654,19 @@ void glTF2Exporter::ExportMaterials()
 
         GetMatTex(mat, m->pbrMetallicRoughness.metallicRoughnessTexture, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_METALLICROUGHNESS_TEXTURE);
 
-        if (GetMatColor(mat, m->pbrMetallicRoughness.baseColorFactor, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_BASE_COLOR_FACTOR) != AI_SUCCESS) {
+        if (GetMatColor(mat, m->pbrMetallicRoughness.baseColorFactor, AI_MATKEY_BASE_COLOR) != 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 (mat->Get(AI_MATKEY_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
             m->pbrMetallicRoughness.metallicFactor = 0;
         }
 
         // get roughness if source is gltf2 file
-        if (mat->Get(AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_ROUGHNESS_FACTOR, m->pbrMetallicRoughness.roughnessFactor) != AI_SUCCESS) {
+        if (mat->Get(AI_MATKEY_ROUGHNESS_FACTOR, m->pbrMetallicRoughness.roughnessFactor) != AI_SUCCESS) {
             // otherwise, try to derive and convert from specular + shininess values
             aiColor4D specularColor;
             ai_real shininess;
@@ -712,36 +712,38 @@ void glTF2Exporter::ExportMaterials()
             }
         }
 
-        bool hasPbrSpecularGlossiness = false;
+        {
-        mat->Get(AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS, hasPbrSpecularGlossiness);
+            // If has a Specular color, use the KHR_materials_pbrSpecularGlossiness extension
-
+            PbrSpecularGlossiness pbrSG;
-        if (hasPbrSpecularGlossiness) {
+            if (GetMatColor(mat, pbrSG.specularFactor, AI_MATKEY_COLOR_SPECULAR) == AI_SUCCESS) {
-
                 if (!mAsset->extensionsUsed.KHR_materials_pbrSpecularGlossiness) {
                     mAsset->extensionsUsed.KHR_materials_pbrSpecularGlossiness = true;
                 }
 
-            PbrSpecularGlossiness pbrSG;
-
                 GetMatColor(mat, pbrSG.diffuseFactor, AI_MATKEY_COLOR_DIFFUSE);
-            GetMatColor(mat, pbrSG.specularFactor, AI_MATKEY_COLOR_SPECULAR);
 
-            if (mat->Get(AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_GLOSSINESS_FACTOR, pbrSG.glossinessFactor) != AI_SUCCESS) {
+                // If don't have explicit glossiness then convert from roughness or shininess
+                if (mat->Get(AI_MATKEY_GLOSSINESS_FACTOR, pbrSG.glossinessFactor) != AI_SUCCESS) {
                     float shininess;
-
+                    if (mat->Get(AI_MATKEY_ROUGHNESS_FACTOR, shininess) == AI_SUCCESS) {
-				if (mat->Get(AI_MATKEY_SHININESS, shininess) == AI_SUCCESS) {
+                        pbrSG.glossinessFactor = 1.0f - shininess;  // Extension defines this way
+                    } else if (mat->Get(AI_MATKEY_SHININESS, shininess) == AI_SUCCESS) {
                         pbrSG.glossinessFactor = shininess / 1000;
                     }
                 }
 
+                // Add any appropriate textures
                 GetMatTex(mat, pbrSG.diffuseTexture, aiTextureType_DIFFUSE);
                 GetMatTex(mat, pbrSG.specularGlossinessTexture, aiTextureType_SPECULAR);
 
                 m->pbrSpecularGlossiness = Nullable<PbrSpecularGlossiness>(pbrSG);
             }
+        }
 
-        bool unlit;
+        // glTFv2 is either PBR or Unlit
-        if (mat->Get(AI_MATKEY_GLTF_UNLIT, unlit) == AI_SUCCESS && unlit) {
+        aiShadingMode shadingMode = aiShadingMode_PBR_BRDF;
+        mat->Get(AI_MATKEY_SHADING_MODEL, shadingMode);
+        if (shadingMode == aiShadingMode_Unlit) {
             mAsset->extensionsUsed.KHR_materials_unlit = true;
             m->unlit = true;
         }

code/AssetLib/glTF2/glTF2Importer.cpp

@@ -238,16 +238,18 @@ static aiMaterial *ImportMaterial(std::vector<int> &embeddedTexIdxs, Asset &r, M
             aimat->AddProperty(&str, AI_MATKEY_NAME);
         }
 
+        // Set Assimp DIFFUSE and BASE COLOR to the pbrMetallicRoughness base color and texture for backwards compatibility
+        // Technically should not load any pbrMetallicRoughness if extensionsRequired contains KHR_materials_pbrSpecularGlossiness
         SetMaterialColorProperty(r, mat.pbrMetallicRoughness.baseColorFactor, aimat, AI_MATKEY_COLOR_DIFFUSE);
-        SetMaterialColorProperty(r, mat.pbrMetallicRoughness.baseColorFactor, aimat, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_BASE_COLOR_FACTOR);
+        SetMaterialColorProperty(r, mat.pbrMetallicRoughness.baseColorFactor, aimat, AI_MATKEY_BASE_COLOR);
 
         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.baseColorTexture, aimat, aiTextureType_BASE_COLOR);
 
         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.metallicFactor, 1, AI_MATKEY_METALLIC_FACTOR);
-        aimat->AddProperty(&mat.pbrMetallicRoughness.roughnessFactor, 1, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_ROUGHNESS_FACTOR);
+        aimat->AddProperty(&mat.pbrMetallicRoughness.roughnessFactor, 1, AI_MATKEY_ROUGHNESS_FACTOR);
 
         float roughnessAsShininess = 1 - mat.pbrMetallicRoughness.roughnessFactor;
         roughnessAsShininess *= roughnessAsShininess * 1000;
@@ -268,22 +270,27 @@ static aiMaterial *ImportMaterial(std::vector<int> &embeddedTexIdxs, Asset &r, M
         if (mat.pbrSpecularGlossiness.isPresent) {
             PbrSpecularGlossiness &pbrSG = mat.pbrSpecularGlossiness.value;
 
-            aimat->AddProperty(&mat.pbrSpecularGlossiness.isPresent, 1, AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS);
             SetMaterialColorProperty(r, pbrSG.diffuseFactor, aimat, AI_MATKEY_COLOR_DIFFUSE);
             SetMaterialColorProperty(r, pbrSG.specularFactor, aimat, AI_MATKEY_COLOR_SPECULAR);
 
             float glossinessAsShininess = pbrSG.glossinessFactor * 1000.0f;
             aimat->AddProperty(&glossinessAsShininess, 1, AI_MATKEY_SHININESS);
-            aimat->AddProperty(&pbrSG.glossinessFactor, 1, AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_GLOSSINESS_FACTOR);
+            aimat->AddProperty(&pbrSG.glossinessFactor, 1, AI_MATKEY_GLOSSINESS_FACTOR);
 
             SetMaterialTextureProperty(embeddedTexIdxs, r, pbrSG.diffuseTexture, aimat, aiTextureType_DIFFUSE);
 
             SetMaterialTextureProperty(embeddedTexIdxs, r, pbrSG.specularGlossinessTexture, aimat, aiTextureType_SPECULAR);
         }
+
+        // glTFv2 is either PBR or Unlit
+        aiShadingMode shadingMode = aiShadingMode_PBR_BRDF;
         if (mat.unlit) {
-            aimat->AddProperty(&mat.unlit, 1, AI_MATKEY_GLTF_UNLIT);
+            shadingMode = aiShadingMode_Unlit;
         }
 
+        aimat->AddProperty(&shadingMode, 1, AI_MATKEY_SHADING_MODEL);
+
+
         //KHR_materials_sheen
         if (mat.materialSheen.isPresent) {
             MaterialSheen &sheen = mat.materialSheen.value;

include/assimp/material.h

@@ -202,11 +202,15 @@ enum aiTextureType {
 
     /** The texture is combined with the result of the diffuse
      *  lighting equation.
+     *  OR
+     *  PBR Specular/Glossiness
      */
     aiTextureType_DIFFUSE = 1,
 
     /** The texture is combined with the result of the specular
      *  lighting equation.
+     *  OR
+     *  PBR Specular/Glossiness
      */
     aiTextureType_SPECULAR = 2,
 
@@ -309,6 +313,8 @@ ASSIMP_API const char *TextureTypeToString(enum aiTextureType in);
 
 // ---------------------------------------------------------------------------
 /** @brief Defines all shading models supported by the library
+ * 
+ *  #AI_MATKEY_SHADING_MODEL
  * 
  *  The list of shading modes has been taken from Blender.
  *  See Blender documentation for more information. The API does
@@ -364,13 +370,27 @@ enum aiShadingMode {
     aiShadingMode_CookTorrance = 0x8,
 
     /** No shading at all. Constant light influence of 1.0.
+    * Also known as "Unlit"
     */
     aiShadingMode_NoShading = 0x9,
+    aiShadingMode_Unlit = aiShadingMode_NoShading, // Alias
 
     /** Fresnel shading
      */
     aiShadingMode_Fresnel = 0xa,
 
+    /** Physically-Based Rendering (PBR) shading using
+    * Bidirectional scattering/reflectance distribution function (BSDF/BRDF)
+    * There are multiple methods under this banner, and model files may provide
+    * data for more than one PBR-BRDF method.
+    * Applications should use the set of provided properties to determine which
+    * of their preferred PBDR methods are available
+    * eg:
+    * - If AI_MATKEY_METALLIC_FACTOR is set, then a Metallic/Roughness is available
+    * - If AI_MATKEY_COLOR_SPECULAR is set, then a Specular/Glossiness is available
+    */
+    aiShadingMode_PBR_BRDF = 0xb,
+
 #ifndef SWIG
     _aiShadingMode_Force32Bit = INT_MAX
 #endif
@@ -923,11 +943,29 @@ extern "C" {
 // ---------------------------------------------------------------------------
 // PBR material support
 #define AI_MATKEY_USE_COLOR_MAP "$mat.useColorMap", 0, 0
+
+// Metallic/Roughness Workflow
+// ---------------------------
+// Base color factor. Will be multiplied by final base color texture values if extant
 #define AI_MATKEY_BASE_COLOR "$clr.base", 0, 0
 #define AI_MATKEY_USE_METALLIC_MAP "$mat.useMetallicMap", 0, 0
+// Metallic factor. 0.0 = Full Dielectric, 1.0 = Full Metal
 #define AI_MATKEY_METALLIC_FACTOR "$mat.metallicFactor", 0, 0
 #define AI_MATKEY_USE_ROUGHNESS_MAP "$mat.useRoughnessMap", 0, 0
+// Roughness factor. 0.0 = Perfectly Smooth, 1.0 = Completely Rough
 #define AI_MATKEY_ROUGHNESS_FACTOR "$mat.roughnessFactor", 0, 0
+
+// Specular/Glossiness Workflow
+// ---------------------------
+// Diffuse/Albedo Color. Note: Pure Metals have a diffuse of {0,0,0}
+// AI_MATKEY_COLOR_DIFFUSE
+// Specular Color
+// AI_MATKEY_COLOR_SPECULAR
+// Glossiness factor. 0.0 = Completely Rough, 1.0 = Perfectly Smooth
+#define AI_MATKEY_GLOSSINESS_FACTOR "$mat.glossinessFactor", 0, 0
+
+// Emissive
+// --------
 #define AI_MATKEY_USE_EMISSIVE_MAP "$mat.useEmissiveMap", 0, 0
 #define AI_MATKEY_EMISSIVE_INTENSITY "$mat.emissiveIntensity", 0, 0
 #define AI_MATKEY_USE_AO_MAP "$mat.useAOMap", 0, 0

include/assimp/pbrmaterial.h

@@ -50,16 +50,16 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #   pragma GCC system_header
 #endif
 
-#define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_BASE_COLOR_FACTOR "$mat.gltf.pbrMetallicRoughness.baseColorFactor", 0, 0
+//#define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_BASE_COLOR_FACTOR "$mat.gltf.pbrMetallicRoughness.baseColorFactor", 0, 0
-#define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_METALLIC_FACTOR "$mat.gltf.pbrMetallicRoughness.metallicFactor", 0, 0
+//#define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_METALLIC_FACTOR "$mat.gltf.pbrMetallicRoughness.metallicFactor", 0, 0
-#define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_ROUGHNESS_FACTOR "$mat.gltf.pbrMetallicRoughness.roughnessFactor", 0, 0
+//#define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_ROUGHNESS_FACTOR "$mat.gltf.pbrMetallicRoughness.roughnessFactor", 0, 0
-#define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_BASE_COLOR_TEXTURE aiTextureType_DIFFUSE, 1
+//#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 "$mat.gltf.pbrSpecularGlossiness", 0, 0
+//#define AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS "$mat.gltf.pbrSpecularGlossiness", 0, 0
-#define AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_GLOSSINESS_FACTOR "$mat.gltf.pbrMetallicRoughness.glossinessFactor", 0, 0
+//#define AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_GLOSSINESS_FACTOR "$mat.gltf.pbrMetallicRoughness.glossinessFactor", 0, 0
-#define AI_MATKEY_GLTF_UNLIT "$mat.gltf.unlit", 0, 0
+//#define AI_MATKEY_GLTF_UNLIT "$mat.gltf.unlit", 0, 0
 #define AI_MATKEY_GLTF_MATERIAL_SHEEN "$mat.gltf.materialSheen", 0, 0
 #define AI_MATKEY_GLTF_MATERIAL_SHEEN_COLOR_FACTOR "$mat.gltf.materialSheen.sheenColorFactor", 0, 0
 #define AI_MATKEY_GLTF_MATERIAL_SHEEN_ROUGHNESS_FACTOR "$mat.gltf.materialSheen.sheenRoughnessFactor", 0, 0

test/unit/utglTF2ImportExport.cpp

@@ -57,10 +57,9 @@ using namespace Assimp;
 
 class utglTF2ImportExport : public AbstractImportExportBase {
 public:
-    virtual bool importerTest() {
+    virtual bool importerMatTest(const char *file, bool spec_gloss, std::array<aiTextureMapMode, 2> exp_modes = { aiTextureMapMode_Wrap, aiTextureMapMode_Wrap }) {
         Assimp::Importer importer;
-        const aiScene *scene = importer.ReadFile(ASSIMP_TEST_MODELS_DIR "/glTF2/BoxTextured-glTF/BoxTextured.gltf",
+        const aiScene *scene = importer.ReadFile(file, aiProcess_ValidateDataStructure);
-                aiProcess_ValidateDataStructure);
         EXPECT_NE(scene, nullptr);
         if (!scene) {
             return false;
@@ -72,13 +71,49 @@ public:
         }
         const aiMaterial *material = scene->mMaterials[0];
 
+        // This Material should be a PBR
+        aiShadingMode shadingMode;
+        EXPECT_EQ(aiReturn_SUCCESS, material->Get(AI_MATKEY_SHADING_MODEL, shadingMode));
+        EXPECT_EQ(aiShadingMode_PBR_BRDF, shadingMode);
+
+        // Should import the texture as diffuse and as base color
         aiString path;
-        aiTextureMapMode modes[2];
+        std::array<aiTextureMapMode,2> modes;
         EXPECT_EQ(aiReturn_SUCCESS, material->GetTexture(aiTextureType_DIFFUSE, 0, &path, nullptr, nullptr,
-                                            nullptr, nullptr, modes));
+                                            nullptr, nullptr, modes.data()));
         EXPECT_STREQ(path.C_Str(), "CesiumLogoFlat.png");
-        EXPECT_EQ(modes[0], aiTextureMapMode_Mirror);
+        EXPECT_EQ(exp_modes, modes);
-        EXPECT_EQ(modes[1], aiTextureMapMode_Clamp);
+
+        // Also as Base Color
+        EXPECT_EQ(aiReturn_SUCCESS, material->GetTexture(aiTextureType_BASE_COLOR, 0, &path, nullptr, nullptr,
+                                            nullptr, nullptr, modes.data()));
+        EXPECT_STREQ(path.C_Str(), "CesiumLogoFlat.png");
+        EXPECT_EQ(exp_modes, modes);
+
+        // Should have a MetallicFactor (default is 1.0)
+        ai_real metal_factor = ai_real(0.5);
+        EXPECT_EQ(aiReturn_SUCCESS, material->Get(AI_MATKEY_METALLIC_FACTOR, metal_factor));
+        EXPECT_EQ(ai_real(0.0), metal_factor);
+
+        // And a roughness factor (default is 1.0)
+        ai_real roughness_factor = ai_real(0.5);
+        EXPECT_EQ(aiReturn_SUCCESS, material->Get(AI_MATKEY_ROUGHNESS_FACTOR, roughness_factor));
+        EXPECT_EQ(ai_real(1.0), roughness_factor);
+
+        aiColor3D spec_color = { 0, 0, 0 };
+        ai_real glossiness = ai_real(0.5);
+        if (spec_gloss) {
+            EXPECT_EQ(aiReturn_SUCCESS, material->Get(AI_MATKEY_COLOR_SPECULAR, spec_color));
+            constexpr ai_real spec_val(0.20000000298023225); // From the file
+            EXPECT_EQ(spec_val, spec_color.r);
+            EXPECT_EQ(spec_val, spec_color.g);
+            EXPECT_EQ(spec_val, spec_color.b);
+            EXPECT_EQ(aiReturn_SUCCESS, material->Get(AI_MATKEY_GLOSSINESS_FACTOR, glossiness));
+            EXPECT_EQ(ai_real(1.0), glossiness);
+        } else {
+            EXPECT_EQ(aiReturn_FAILURE, material->Get(AI_MATKEY_COLOR_SPECULAR, spec_color));
+            EXPECT_EQ(aiReturn_FAILURE, material->Get(AI_MATKEY_GLOSSINESS_FACTOR, glossiness));
+        }
 
         return true;
     }
@@ -105,13 +140,17 @@ public:
 };
 
 TEST_F(utglTF2ImportExport, importglTF2FromFileTest) {
-    EXPECT_TRUE(importerTest());
+    EXPECT_TRUE(importerMatTest(ASSIMP_TEST_MODELS_DIR "/glTF2/BoxTextured-glTF/BoxTextured.gltf", false, {aiTextureMapMode_Mirror, aiTextureMapMode_Clamp}));
 }
 
 TEST_F(utglTF2ImportExport, importBinaryglTF2FromFileTest) {
     EXPECT_TRUE(binaryImporterTest());
 }
 
+TEST_F(utglTF2ImportExport, importglTF2_KHR_materials_pbrSpecularGlossiness) {
+    EXPECT_TRUE(importerMatTest(ASSIMP_TEST_MODELS_DIR "/glTF2/BoxTextured-glTF-pbrSpecularGlossiness/BoxTextured.gltf", true));
+}
+
 #ifndef ASSIMP_BUILD_NO_EXPORT
 TEST_F(utglTF2ImportExport, importglTF2AndExportToOBJ) {
     Assimp::Importer importer;