[+] Flag for scene for supporting formats where more than one face can reference to one vertex.

code/ValidateDataStructure.cpp

@@ -1,4 +1,4 @@
-/*
+/*
 ---------------------------------------------------------------------------
 Open Asset Import Library (assimp)
 ---------------------------------------------------------------------------
@@ -408,7 +408,8 @@ void ValidateDSProcess::Validate( const aiMesh* pMesh)
             // the MSB flag is temporarily used by the extra verbose
             // mode to tell us that the JoinVerticesProcess might have
             // been executed already.
-            if ( !(this->mScene->mFlags & AI_SCENE_FLAGS_NON_VERBOSE_FORMAT ) && abRefList[face.mIndices[a]])
+			if ( !(this->mScene->mFlags & AI_SCENE_FLAGS_NON_VERBOSE_FORMAT ) && !(this->mScene->mFlags & AI_SCENE_FLAGS_ALLOW_SHARED) &&
+				abRefList[face.mIndices[a]])
             {
                 ReportError("aiMesh::mVertices[%i] is referenced twice - second "
                     "time by aiMesh::mFaces[%i]::mIndices[%i]",face.mIndices[a],i,a);

include/assimp/scene.h

@@ -1,4 +1,4 @@
-/*
+/*
 ---------------------------------------------------------------------------
 Open Asset Import Library (assimp)
 ---------------------------------------------------------------------------
@@ -266,6 +266,13 @@ struct aiNode
  */
 #define AI_SCENE_FLAGS_TERRAIN 0x10
 
+ /**
+ * Specifies that the scene data can be shared between structures. For example:
+ * one vertex in few faces. \ref AI_SCENE_FLAGS_NON_VERBOSE_FORMAT can not be
+ * used for this because \ref AI_SCENE_FLAGS_NON_VERBOSE_FORMAT has internal
+ * meaning about postprocessing steps.
+ */
+#define AI_SCENE_FLAGS_ALLOW_SHARED			0x20
 
 // -------------------------------------------------------------------------------
 /** The root structure of the imported data.