ExtrudeShape when use convertToFlatShade,ArcSide light is not good

like: Babylon.js Playground
In left, when i use leftShape and extrudeShape then convertToFlatShade,the arc side light is not good,
but in right, i modify leftShape to rightShape,then use extrudeShape and convertToUnIndexedMesh,the rightShapeMesh side light is good,
so when i went to us leftshape,the effect looks like rightShapeMesh,how to do?

I am not sure to fully understand the question :frowning: Maybe @Evgeni_Popov would know ?

I didn’t understand neither. The left rendering is what is expected when using convertToFlatShadedMesh as each face/vertex will get its own normal that won’t be shared with other faces.

convertToUnIndexedMesh simply converts the mesh to an unindexed mesh, which does not impact how it is rendered.

In picture, I want face 1 look like face 4, face 2 looks like face3,how to do?
In Left,each face has its own normal,but i want face 2 has its own normal,but face 1 shared with other faces to look like smooth effect(like face 4 effect)

Except by splitting the mesh into two meshes and applying convertToFlatShadedMesh to one of the mesh and not to the other, I don’t see how you can do it… Or you would need to create the normals yourself to achieve the rendering you want.