Three.js: How to flip normals after negative scale

Question

I have cloned and than flipped an object using negative scale, which causes my single sided faces to inverse. My question is, how can i flip the normals too?

I don\'

Answer 1

This question is two years old, but in case anyone passes by. Here is a non-destructive way of doing this:

You can enter the "dirty vertices/normals" mode, and flip the normals manually:

mesh.geometry.dynamic = true
mesh.geometry.__dirtyVertices = true;
mesh.geometry.__dirtyNormals = true;

mesh.flipSided = true;

//flip every vertex normal in mesh by multiplying normal by -1
for(var i = 0; i

+1 @WestLangley, I suggest you never use negative scale.