BabylonExporter Right->Left Coordinate System

[ProfessorF]

I noticed that my Maya model:

 

Was coming out backwards in Babylon:

 

I eventually figured out that it was because Maya is a right-handed coordinate system & Babylon.js is left-handed.  I think it's most efficient to code the transformation in the BabylonExporter, so I did the following:

 

1. Change the winding of the triangles (otherwise faces become invisible)

2. Invert Z position

3. Invert Z normal

 

The relevant code in BabylonExport.Core > Exporters > ThroughXNA > XNAExporter.cs

 

        void ParseMesh(ModelMesh modelMesh, BabylonScene scene, BabylonSkeleton skeleton)

        {

            var proxyID = ProxyMesh.CreateBabylonMesh(modelMesh.Name, scene);

            int indexName = 0;

 

            foreach (var part in modelMesh.MeshParts)

            {

                var material = exportedMaterials.First(m => m.Name == part.Effect.GetHashCode().ToString());

 

                var indices = new ushort[part.PrimitiveCount * 3];

                                

                part.IndexBuffer.GetData(part.StartIndex * 2, indices, 0, indices.Length);

                for (int ib = 0; ib < indices.Length; ib += 3) // reverse winding of triangles

                {

                    ushort ti;

                    ti = indices[ib];

                    indices[ib] = indices[ib + 2];

                    indices[ib + 2] = ti;

                }

                

                

                if (part.VertexBuffer.VertexDeclaration.VertexStride >= PositionNormalTexturedWeights.Stride)

                {

                    var mesh = new Mesh<PositionNormalTexturedWeights>(material);

                    var vertices = new PositionNormalTexturedWeights[part.NumVertices];

 

                    part.VertexBuffer.GetData(part.VertexOffset * part.VertexBuffer.VertexDeclaration.VertexStride, vertices, 0, vertices.Length, part.VertexBuffer.VertexDeclaration.VertexStride);

 

                    for (int index = 0; index < vertices.Length; index++)

                    {

                        vertices[index].TextureCoordinates.Y = 1.0f - vertices[index].TextureCoordinates.Y;

                        vertices[index].Position.Z = -vertices[index].Position.Z;

                        vertices[index].Normal.Z = -vertices[index].Normal.Z;

                    }

 

                    mesh.AddPart(indexName.ToString(), vertices.ToList(), indices.Select(i => (int)i).ToList());

                    mesh.CreateBabylonMesh(scene, proxyID, skeleton);

                }

                else

                {

                    if (part.VertexBuffer.VertexDeclaration.VertexStride < 32) return;

                    var mesh = new Mesh<PositionNormalTextured>(material);

                    var vertices = new PositionNormalTextured[part.NumVertices];

                    part.VertexBuffer.GetData(part.VertexOffset * part.VertexBuffer.VertexDeclaration.VertexStride, vertices, 0, vertices.Length, part.VertexBuffer.VertexDeclaration.VertexStride);

 

                    for (int index = 0; index < vertices.Length; index++)

                    {

                        vertices[index].TextureCoordinates.Y = 1.0f - vertices[index].TextureCoordinates.Y;

                        vertices[index].Position.Z = -vertices[index].Position.Z;

                        vertices[index].Normal.Z = -vertices[index].Normal.Z;

                    }

 

                    mesh.AddPart(indexName.ToString(), vertices.ToList(), indices.Select(i => (int)i).ToList());

                    mesh.CreateBabylonMesh(scene, proxyID, skeleton);

                }

 

                indexName++;

            }

        }

 

 

This fixed the problem:

 

 

DeltaKosh, should this be a permanent fix, or maybe can you add a flag to the command-line (/rightleft ?) , to invoke the green code? 

 

 

[GameMonetize]

Hello Prof, it can't be a permanent fix because the FBX can be left handed (my dude.fbx is left handed for instance) but I can easily add the switch

[GameMonetize]

I added a "/rl" to the new version

 

You can try it here:

 

http://www.babylonjs.com/prof.zip

[ProfessorF]

Thanks!