Cannot export correct ply file after remesh function.

[zhangzhousuper]

Hi,
What I have done to encounter this problem is:

1. Load a ply mesh.
   2.Decimate the mesh and export a ply mesh file, which is perfect.
2. Then remesh the mesh and try to export a ply mesh file like
   MR::remesh(mesh, remesh_set); MR::MeshSave::toAnySupportedFormat(mesh, "first_remesh.ply", save_set); .And the export progress will crash. I try to export the stl file, which can export correctly but cannot have vert color. Besides, if I want to export that stl file to ply, it's also undoable :<

Do u guys have any advice for me to export the ply file?

[Grantim]

Hello!
Could you please provide mesh and small code example so we could reproduce the crash?

[zhangzhousuper]

Sure!

test.zip

[Grantim]

Looks like the issue is that you have invalid colors vector, you need to update it on decimation and remesh. It works with decimation because decimation does not produce new vertices, and color vector has valid size (while colors are still not updated correctly), but remesh produce new vertices and color vector after it is smaller than it should be (and not updated).

I suggest you to add update code like this, so your color vector will stay valid and updated.

    MR::VertColors temp;
    MR::MeshLoadSettings mls;
    mls.colors = &temp;
    MR::Mesh mesh = *MR::MeshLoad::fromAnySupportedFormat("test.ply", mls);
    MR::SaveSettings points_save_set;
    points_save_set.colors = &temp;

    std::function<bool( EdgeId edgeToCollapse, const Vector3f& newEdgeOrgPos )> preCollapse = [&] ( EdgeId edgeToCollapse, const Vector3f& newEdgeOrgPos )
    {
        auto org = mesh.topology.org( edgeToCollapse );
        auto dest = mesh.topology.dest( edgeToCollapse );
        auto edgeVec = mesh.edgeVector( edgeToCollapse );
        auto lSq = edgeVec.lengthSq();
        float ratioOrg = dot( newEdgeOrgPos - mesh.points[org], edgeVec ) / lSq;
        float ratioDest = dot( newEdgeOrgPos - mesh.points[dest], -edgeVec ) / lSq;
        float ratio = ratioOrg / ( ratioOrg + ratioDest );
        temp[org] = Color( Vector4f( temp[org] ) * ( 1.0f - ratio ) + Vector4f( temp[dest] ) * ( ratio ) );
    };
    std::function<void( EdgeId e1, EdgeId e )> onEdgeSplit = [&] ( EdgeId e1, EdgeId e )
    {
        auto org = mesh.topology.org( e1 );
        auto mid = mesh.topology.dest( e1 );
        assert( mid == mesh.topology.org( e ) );
        auto dest = mesh.topology.dest( e );

        temp.autoResizeSet( mid, Color( Vector4f( temp[org] ) * 0.5f + Vector4f( temp[dest] ) * 0.5f ) );
    };


    MR::RemeshSettings remesh_set;
    MR::DecimateSettings decimate_set;

    remesh_set.preCollapse = preCollapse;
    remesh_set.onEdgeSplit = onEdgeSplit;
    decimate_set.preCollapse = preCollapse;

Please let me now if it helps!

[zhangzhousuper]

Thanks a lot! BTW, Could you provide possibility to have export ply models in ASCII.

[Grantim]

Now we only export binary ply, it has advantage in file size and precision.