Avoid setting metallic/roughness/sheen/clearcoat properties when they are not found on mtl file.

code/AssetLib/Obj/ObjFileData.h

@@ -43,6 +43,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #ifndef OBJ_FILEDATA_H_INC
 #define OBJ_FILEDATA_H_INC
 
+#include <Common/maybe.h>
 #include <assimp/mesh.h>
 #include <assimp/types.h>
 #include <map>
@@ -183,15 +184,15 @@ struct Material {
     aiColor3D transparent;
 
     //! PBR Roughness
-    ai_real roughness;
+    Maybe<ai_real> roughness;
     //! PBR Metallic
-    ai_real metallic;
+    Maybe<ai_real> metallic;
     //! PBR Metallic
-    aiColor3D sheen;
+    Maybe<aiColor3D> sheen;
     //! PBR Clearcoat Thickness
-    ai_real clearcoat_thickness;
+    Maybe<ai_real> clearcoat_thickness;
     //! PBR Clearcoat Rougness
-    ai_real clearcoat_roughness;
+    Maybe<ai_real> clearcoat_roughness;
     //! PBR Anisotropy
     ai_real anisotropy;
 
@@ -206,11 +207,11 @@ struct Material {
             illumination_model(1),
             ior(ai_real(1.0)),
             transparent(ai_real(1.0), ai_real(1.0), ai_real(1.0)),
-            roughness(ai_real(1.0)),
+            roughness(),
-            metallic(ai_real(0.0)),
+            metallic(),
-            sheen(ai_real(1.0), ai_real(1.0), ai_real(1.0)),
+            sheen(),
-            clearcoat_thickness(ai_real(0.0)),
+            clearcoat_thickness(),
-            clearcoat_roughness(ai_real(0.0)),
+            clearcoat_roughness(),
             anisotropy(ai_real(0.0)),
             bump_multiplier(ai_real(1.0)) {
         std::fill_n(clamp, static_cast<unsigned int>(TextureTypeCount), false);

code/AssetLib/Obj/ObjFileImporter.cpp

@@ -616,11 +616,16 @@ void ObjFileImporter::createMaterials(const ObjFile::Model *pModel, aiScene *pSc
         mat->AddProperty(&pCurrentMaterial->shineness, 1, AI_MATKEY_SHININESS);
         mat->AddProperty(&pCurrentMaterial->alpha, 1, AI_MATKEY_OPACITY);
         mat->AddProperty(&pCurrentMaterial->transparent, 1, AI_MATKEY_COLOR_TRANSPARENT);
-        mat->AddProperty(&pCurrentMaterial->roughness, 1, AI_MATKEY_ROUGHNESS_FACTOR);
+        if (pCurrentMaterial->roughness)
-        mat->AddProperty(&pCurrentMaterial->metallic, 1, AI_MATKEY_METALLIC_FACTOR);
+            mat->AddProperty(&pCurrentMaterial->roughness.Get(), 1, AI_MATKEY_ROUGHNESS_FACTOR);
-        mat->AddProperty(&pCurrentMaterial->sheen, 1, AI_MATKEY_SHEEN_COLOR_FACTOR);
+        if (pCurrentMaterial->metallic)
-        mat->AddProperty(&pCurrentMaterial->clearcoat_thickness, 1, AI_MATKEY_CLEARCOAT_FACTOR);
+            mat->AddProperty(&pCurrentMaterial->metallic.Get(), 1, AI_MATKEY_METALLIC_FACTOR);
-        mat->AddProperty(&pCurrentMaterial->clearcoat_roughness, 1, AI_MATKEY_CLEARCOAT_ROUGHNESS_FACTOR);
+        if (pCurrentMaterial->sheen)
+            mat->AddProperty(&pCurrentMaterial->sheen.Get(), 1, AI_MATKEY_SHEEN_COLOR_FACTOR);
+        if (pCurrentMaterial->clearcoat_thickness)
+            mat->AddProperty(&pCurrentMaterial->clearcoat_thickness.Get(), 1, AI_MATKEY_CLEARCOAT_FACTOR);
+        if (pCurrentMaterial->clearcoat_roughness)
+            mat->AddProperty(&pCurrentMaterial->clearcoat_roughness.Get(), 1, AI_MATKEY_CLEARCOAT_ROUGHNESS_FACTOR);
         mat->AddProperty(&pCurrentMaterial->anisotropy, 1, AI_MATKEY_ANISOTROPY_FACTOR);
 
         // Adding refraction index

code/AssetLib/Obj/ObjFileMtlImporter.cpp

@@ -205,7 +205,7 @@ void ObjFileMtlImporter::load() {
                         break;
                     case 's':
                         ++m_DataIt;
-                        getColorRGBA(&m_pModel->m_pCurrentMaterial->sheen);
+                        getColorRGBA(m_pModel->m_pCurrentMaterial->sheen);
                         break;
                     case 'c':
                         ++m_DataIt;
@@ -267,6 +267,12 @@ void ObjFileMtlImporter::getColorRGBA(aiColor3D *pColor) {
     pColor->b = b;
 }
 
+void ObjFileMtlImporter::getColorRGBA(Maybe<aiColor3D> &value) {
+    aiColor3D v;
+    getColorRGBA(&v);
+    value = Maybe<aiColor3D>(v);
+}
+
 // -------------------------------------------------------------------
 //  Loads the kind of illumination model.
 void ObjFileMtlImporter::getIlluminationModel(int &illum_model) {
@@ -274,6 +280,7 @@ void ObjFileMtlImporter::getIlluminationModel(int &illum_model) {
     illum_model = atoi(&m_buffer[0]);
 }
 
+
 // -------------------------------------------------------------------
 //  Loads a single float value.
 void ObjFileMtlImporter::getFloatValue(ai_real &value) {
@@ -283,10 +290,19 @@ void ObjFileMtlImporter::getFloatValue(ai_real &value) {
         value = 0.0f;
         return;
     }
-    
+
     value = (ai_real)fast_atof(&m_buffer[0]);
 }
 
+void ObjFileMtlImporter::getFloatValue(Maybe<ai_real> &value) {
+    m_DataIt = CopyNextWord<DataArrayIt>(m_DataIt, m_DataItEnd, &m_buffer[0], BUFFERSIZE);
+    size_t len = std::strlen(&m_buffer[0]);
+    if (len)
+        value = Maybe<ai_real>(fast_atof(&m_buffer[0]));
+    else
+        value = Maybe<ai_real>();
+}
+
 // -------------------------------------------------------------------
 //  Creates a material from loaded data.
 void ObjFileMtlImporter::createMaterial() {

code/AssetLib/Obj/ObjFileMtlImporter.h

@@ -40,6 +40,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #ifndef OBJFILEMTLIMPORTER_H_INC
 #define OBJFILEMTLIMPORTER_H_INC
 
+#include <Common/maybe.h>
 #include <assimp/defs.h>
 #include <string>
 #include <vector>
@@ -81,10 +82,12 @@ private:
     void load();
     /// Get color data.
     void getColorRGBA(aiColor3D *pColor);
+    void getColorRGBA(Maybe<aiColor3D> &value);
     /// Get illumination model from loaded data
     void getIlluminationModel(int &illum_model);
     /// Gets a float value from data.
     void getFloatValue(ai_real &value);
+    void getFloatValue(Maybe<ai_real> &value);
     /// Creates a new material from loaded data.
     void createMaterial();
     /// Get texture name from loaded data.

code/CMakeLists.txt

@@ -181,6 +181,7 @@ SET( Common_SRCS
   Common/DefaultIOSystem.cpp
   Common/ZipArchiveIOSystem.cpp
   Common/PolyTools.h
+  Common/Maybe.h
   Common/Importer.cpp
   Common/IFF.h
   Common/SGSpatialSort.cpp

code/Common/Maybe.h

@@ -0,0 +1,29 @@
+#pragma once
+#include <assimp/ai_assert.h>
+
+template <typename T>
+struct Maybe {
+private:
+    T _val;
+    bool _valid;
+
+public:
+    Maybe() :
+            _valid(false) {}
+
+    explicit Maybe(const T &val) :
+            _valid(true), _val(val) {
+    }
+
+    operator bool() const {
+        return _valid;
+    }
+
+    const T &Get() const {
+        ai_assert(_valid);
+        return _val;
+    }
+
+private:
+    Maybe &operator&() = delete;
+};