Always pre-transform vertices while reading with Assimp.

cpp/open3d/io/TriangleMeshIO.h

@@ -31,6 +31,7 @@ struct ReadTriangleMeshOptions {
     /// `aiProcessPreset_TargetRealtime_Fast,
     /// aiProcess_RemoveRedundantMaterials, aiProcess_OptimizeMeshes,
     /// aiProcess_PreTransformVertices`.
+    /// https://github.com/assimp/assimp/blob/master/include/assimp/postprocess.h
     ///
     /// Note that identical vertices will always be joined regardless of whether
     /// post-processing is enabled or not, which changes the number of vertices

cpp/open3d/io/file_format/FileASSIMP.cpp

@@ -36,13 +36,16 @@ FileGeometry ReadFileGeometryTypeFBX(const std::string& path) {
     return FileGeometry(CONTAINS_TRIANGLES | CONTAINS_POINTS);
 }
 
+// Ref:
+// https://github.com/assimp/assimp/blob/master/include/assimp/postprocess.h
 const unsigned int kPostProcessFlags_compulsory =
-        aiProcess_JoinIdenticalVertices;
+        aiProcess_JoinIdenticalVertices | aiProcess_SortByPType |
+        aiProcess_PreTransformVertices;
 
 const unsigned int kPostProcessFlags_fast =
-        aiProcessPreset_TargetRealtime_Fast |
-        aiProcess_RemoveRedundantMaterials | aiProcess_OptimizeMeshes |
-        aiProcess_PreTransformVertices;
+        kPostProcessFlags_compulsory | aiProcess_GenNormals |
+        aiProcess_Triangulate | aiProcess_GenUVCoords |
+        aiProcess_RemoveRedundantMaterials | aiProcess_OptimizeMeshes;
 
 struct TextureImages {
     std::shared_ptr<geometry::Image> albedo;
@@ -65,7 +68,7 @@ void LoadTextures(const std::string& filename,
     std::string base_path =
             utility::filesystem::GetFileParentDirectory(filename);
 
-    auto texture_loader = [&base_path, &scene, &mat](
+    auto texture_loader = [&base_path, &scene, &mat, &filename](
                                   aiTextureType type,
                                   std::shared_ptr<geometry::Image>& img) {
         if (mat->GetTextureCount(type) > 0) {
@@ -94,7 +97,10 @@ void LoadTextures(const std::string& filename,
                     }
                 } else {
                     utility::LogWarning(
-                            "This format of image is not supported.");
+                            "Unsupported texture format for texture {} for "
+                            "file {}: Only jpg and "
+                            "png textures are supported.",
+                            path.C_Str(), filename);
                 }
             }
             // Else, build the path to it.
@@ -170,7 +176,8 @@ bool ReadTriangleMeshUsingASSIMP(
 
     const auto* scene = importer.ReadFile(filename.c_str(), post_process_flags);
     if (!scene) {
-        utility::LogWarning("Unable to load file {} with ASSIMP", filename);
+        utility::LogWarning("Unable to load file {} with ASSIMP: {}", filename,
+                            importer.GetErrorString());
         return false;
     }
 
@@ -326,7 +333,8 @@ bool ReadModelUsingAssimp(const std::string& filename,
     const auto* scene =
             importer.ReadFile(filename.c_str(), kPostProcessFlags_fast);
     if (!scene) {
-        utility::LogWarning("Unable to load file {} with ASSIMP", filename);
+        utility::LogWarning("Unable to load file {} with ASSIMP: {}", filename,
+                            importer.GetErrorString());
         return false;
     }
 

cpp/open3d/t/io/file_format/FileASSIMP.cpp

@@ -35,14 +35,16 @@ namespace t {
 namespace io {
 
 // Split all polygons with more than 3 edges into triangles.
+// Ref:
+// https://github.com/assimp/assimp/blob/master/include/assimp/postprocess.h
 const unsigned int kPostProcessFlags_compulsory =
         aiProcess_JoinIdenticalVertices | aiProcess_Triangulate |
-        aiProcess_SortByPType;
+        aiProcess_SortByPType | aiProcess_PreTransformVertices;
 
 const unsigned int kPostProcessFlags_fast =
-        aiProcessPreset_TargetRealtime_Fast |
-        aiProcess_RemoveRedundantMaterials | aiProcess_OptimizeMeshes |
-        aiProcess_PreTransformVertices;
+        kPostProcessFlags_compulsory | aiProcess_GenNormals |
+        aiProcess_GenUVCoords | aiProcess_RemoveRedundantMaterials |
+        aiProcess_OptimizeMeshes;
 
 bool ReadTriangleMeshUsingASSIMP(
         const std::string& filename,
@@ -58,7 +60,8 @@ bool ReadTriangleMeshUsingASSIMP(
 
     const auto* scene = importer.ReadFile(filename.c_str(), post_process_flags);
     if (!scene) {
-        utility::LogWarning("Unable to load file {} with ASSIMP", filename);
+        utility::LogWarning("Unable to load file {} with ASSIMP: {}", filename,
+                            importer.GetErrorString());
         return false;
     }
 
@@ -219,7 +222,7 @@ bool WriteTriangleMeshUsingASSIMP(const std::string& filename,
     // Sanity checks...
     if (write_ascii) {
         utility::LogWarning(
-                "TriangleMesh can't be saved in ASCII fromat as .glb");
+                "TriangleMesh can't be saved in ASCII format as .glb");
         return false;
     }
     if (compressed) {
@@ -470,7 +473,9 @@ bool WriteTriangleMeshUsingASSIMP(const std::string& filename,
     // Export
     if (exporter.Export(ai_scene.get(), "glb2", filename.c_str()) ==
         AI_FAILURE) {
-        utility::LogWarning("Got error: {}", exporter.GetErrorString());
+        utility::LogWarning(
+                "Got error: ({}) while writing TriangleMesh to file {}.",
+                exporter.GetErrorString(), filename);
         return false;
     }