[ObjExporter] add a "no mtl" version of the obj exporter

code/Exporter.cpp

@@ -83,6 +83,7 @@ void ExportSceneCollada(const char*,IOSystem*, const aiScene*, const ExportPrope
 void ExportSceneXFile(const char*,IOSystem*, const aiScene*, const ExportProperties*);
 void ExportSceneStep(const char*,IOSystem*, const aiScene*, const ExportProperties*);
 void ExportSceneObj(const char*,IOSystem*, const aiScene*, const ExportProperties*);
+void ExportSceneObjNoMtl(const char*,IOSystem*, const aiScene*, const ExportProperties*);
 void ExportSceneSTL(const char*,IOSystem*, const aiScene*, const ExportProperties*);
 void ExportSceneSTLBinary(const char*,IOSystem*, const aiScene*, const ExportProperties*);
 void ExportScenePly(const char*,IOSystem*, const aiScene*, const ExportProperties*);
@@ -115,6 +116,8 @@ Exporter::ExportFormatEntry gExporters[] =
 #ifndef ASSIMP_BUILD_NO_OBJ_EXPORTER
     Exporter::ExportFormatEntry( "obj", "Wavefront OBJ format", "obj", &ExportSceneObj,
         aiProcess_GenSmoothNormals /*| aiProcess_PreTransformVertices */),
+    Exporter::ExportFormatEntry( "objnomtl", "Wavefront OBJ format without material file", "obj", &ExportSceneObjNoMtl,
+        aiProcess_GenSmoothNormals /*| aiProcess_PreTransformVertices */),
 #endif
 
 #ifndef ASSIMP_BUILD_NO_STL_EXPORTER

code/ObjExporter.cpp

@@ -83,12 +83,34 @@ void ExportSceneObj(const char* pFile,IOSystem* pIOSystem, const aiScene* pScene
     }
 }
 
+// ------------------------------------------------------------------------------------------------
+// Worker function for exporting a scene to Wavefront OBJ without the material file. Prototyped and registered in Exporter.cpp
+void ExportSceneObjNoMtl(const char* pFile,IOSystem* pIOSystem, const aiScene* pScene, const ExportProperties* pProperties) {
+    // invoke the exporter
+    ObjExporter exporter(pFile, pScene, true);
+
+    if (exporter.mOutput.fail() || exporter.mOutputMat.fail()) {
+        throw DeadlyExportError("output data creation failed. Most likely the file became too large: " + std::string(pFile));
+    }
+
+    // we're still here - export successfully completed. Write both the main OBJ file and the material script
+    {
+        std::unique_ptr<IOStream> outfile (pIOSystem->Open(pFile,"wt"));
+        if(outfile == NULL) {
+            throw DeadlyExportError("could not open output .obj file: " + std::string(pFile));
+        }
+        outfile->Write( exporter.mOutput.str().c_str(), static_cast<size_t>(exporter.mOutput.tellp()),1);
+    }
+
+
+}
+
 } // end of namespace Assimp
 
 static const std::string MaterialExt = ".mtl";
 
 // ------------------------------------------------------------------------------------------------
-ObjExporter::ObjExporter(const char* _filename, const aiScene* pScene)
+ObjExporter::ObjExporter(const char* _filename, const aiScene* pScene, bool noMtl)
 : filename(_filename)
 , pScene(pScene)
 , vp()
@@ -108,7 +130,8 @@ ObjExporter::ObjExporter(const char* _filename, const aiScene* pScene)
     mOutputMat.imbue(l);
     mOutputMat.precision(16);
 
-    WriteGeometryFile();
+    WriteGeometryFile(noMtl);
+    if (!noMtl)
         WriteMaterialFile();
 }
 
@@ -236,8 +259,9 @@ void ObjExporter::WriteMaterialFile()
 }
 
 // ------------------------------------------------------------------------------------------------
-void ObjExporter::WriteGeometryFile() {
+void ObjExporter::WriteGeometryFile(bool noMtl) {
     WriteHeader(mOutput);
+    if (!noMtl)
         mOutput << "mtllib "  << GetMaterialLibName() << endl << endl;
 
     // collect mesh geometry
@@ -284,6 +308,7 @@ void ObjExporter::WriteGeometryFile() {
         if (!m.name.empty()) {
             mOutput << "g " << m.name << endl;
         }
+        if (!noMtl)
             mOutput << "usemtl " << m.matname << endl;
 
         for(const Face& f : m.faces) {

code/ObjExporter.h

@@ -62,7 +62,7 @@ namespace Assimp {
 class ObjExporter {
 public:
     /// Constructor for a specific scene to export
-    ObjExporter(const char* filename, const aiScene* pScene);
+    ObjExporter(const char* filename, const aiScene* pScene, bool noMtl=false);
     ~ObjExporter();
     std::string GetMaterialLibName();
     std::string GetMaterialLibFileName();
@@ -97,7 +97,7 @@ private:
 
     void WriteHeader(std::ostringstream& out);
     void WriteMaterialFile();
-    void WriteGeometryFile();
+    void WriteGeometryFile(bool noMtl=false);
     std::string GetMaterialName(unsigned int index);
     void AddMesh(const aiString& name, const aiMesh* m, const aiMatrix4x4& mat);
     void AddNode(const aiNode* nd, const aiMatrix4x4& mParent);