bugfix: Fixed the issue that draco compressed gltf files cannot be loaded normally (#5882) (#5883)

Co-authored-by: Kim Kulling <[email protected]>

code/AssetLib/glTF2/glTF2Asset.inl

@@ -294,6 +294,8 @@ inline void SetDecodedIndexBuffer_Draco(const draco::Mesh &dracoMesh, Mesh::Prim
     // Usually uint32_t but shouldn't assume
     if (sizeof(dracoMesh.face(draco::FaceIndex(0))[0]) == componentBytes) {
         memcpy(decodedIndexBuffer->GetPointer(), &dracoMesh.face(draco::FaceIndex(0))[0], decodedIndexBuffer->byteLength);
+        // Assign this alternate data buffer to the accessor
+        prim.indices->decodedBuffer.swap(decodedIndexBuffer);
         return;
     }
 

test/unit/utglTF2ImportExport.cpp

@@ -896,6 +896,27 @@ TEST_F(utglTF2ImportExport, import_dracoEncoded) {
         ASSERT_TRUE(scene->mMetaData->Get(AI_METADATA_SOURCE_GENERATOR, generator));
         ASSERT_EQ(strcmp(generator.C_Str(), "COLLADA2GLTF"), 0);
     }
+#endif
+    const aiScene *robotScene = importer.ReadFile(ASSIMP_TEST_MODELS_DIR "/glTF2/draco/robot.glb",
+        aiProcess_ValidateDataStructure);
+#ifndef ASSIMP_ENABLE_DRACO
+    // No draco support, scene should not load
+    ASSERT_EQ(robotScene, nullptr);
+#else
+    ASSERT_NE(robotScene, nullptr);
+    ASSERT_NE(robotScene->mMetaData, nullptr);
+    {
+        ASSERT_TRUE(robotScene->mMetaData->HasKey(AI_METADATA_SOURCE_FORMAT));
+        aiString format;
+        ASSERT_TRUE(robotScene->mMetaData->Get(AI_METADATA_SOURCE_FORMAT, format));
+        ASSERT_EQ(strcmp(format.C_Str(), "glTF2 Importer"), 0);
+    }
+    {
+        ASSERT_TRUE(robotScene->mMetaData->HasKey(AI_METADATA_SOURCE_FORMAT_VERSION));
+        aiString version;
+        ASSERT_TRUE(robotScene->mMetaData->Get(AI_METADATA_SOURCE_FORMAT_VERSION, version));
+        ASSERT_EQ(strcmp(version.C_Str(), "2.0"), 0);
+    }
 #endif
 }