Hi Pilou,

> There is not this problem with other progs like modo c4d ...?

No, it's not a problem with other rendering programs - both Modo and Cinema4D for example will load vertex normals from a file and then be able to use those vertex normals for shading when rendering.

Blender is pretty unique in just ignoring them, and it's especially unique when it comes to rendering - when it renders it ignores any existing vertex normals and recalculates some new ones just for the render. This is pretty weird because it makes the render look different than what is actually present in the model data and from what is being displayed in the realtime view (when you may have managed to get normals loaded in the first place).

Unfortunately this makes rendering many kinds of CAD data pretty difficult with Blender, because it is important with CAD data to make use of the normals that come from the original surfaces.

So anyway in this area of getting high quality shading from CAD data, Blender is far far behind pretty much every other rendering program out there because of this.

- Michael