Transforming a plane with a matrix doesn't produce correct normal

[baothientran]

When transforming a plane with a matrix, the plane's normal is currently multiplied with the transform matrix itself. However, the transform matrix should be converted to normal matrix before multiplying with normal. This is the sandcastle's example(Notice the angle printed out on the console)

This also happens in the czm_transformPlane() glsl function

Another explanation from stack overflow:
https://stackoverflow.com/questions/7685495/transforming-a-3d-plane-using-a-4x4-matrix

[OmarShehata]

Is this related to #8268 at all?

[baothientran]

I think it is related as well since in the createPrimitiveModel() function, the normal is directly multiplied with the transform matrix instead of the normal matrix.