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

But also - these issues were fixed for Blender 2.49 with Anthony's work.

He implemented an importer that would load the vertex normals in (forum thread here), and also at one point made a custom Blender build that would not throw away the normals for rendering (forum thread here).

However, the old import script does not work anymore with the new Blender version, and the patched version is an older version.

So those previous workarounds do not really help for the latest Blender release.

It's just too bad that it's not fixed up directly in the main Blender version instead of needing workarounds in the first place...

- Michael

>> 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.

Do Modo and C4D have problems when a mesh is edited (or at other times)? In other words, are there times when Modo or C4D recalculate vertex normals and you end up with a bad model once again?

Hi YHWH_777,

> Do Modo and C4D have problems when a mesh is
> edited (or at other times)?

Yeah there are a few quirks here that could still use some tuning in Modo, like if you're in vertex mode and transform all vertices the vertex normals do not get transformed in that case. So you kind of need to watch out how you're transforming your object and transform it in "item mode" where the entire object is handled as one piece.

But just loading a file and then rendering it is fine.

There's a pretty huge difference though between having things get messed up in some particular circumstance that is avoidable, versus having no way to have things get shaded properly at all which is the case in Blender right now.


It is expected that if you yank some individual points around, that the vertex normals should then be recalculated - the vertex normals control how shading is applied to your object so it is tied to the shape of the object. If you pull some points around and change its shape, then that's when it does make sense for the normals to be discarded and recalculated because you don't want the new shape to have the old shading.

But pretty much anything other than that should keep the vertex normals intact.


- Michael

Maybe something here
http://blenderartists.org/forum/showthread.php?182195-OBJ-import-normals

Hi Pilou, yup that discussion thread is talking about this exact problem.

Anthony says in that thread there that he sent the patch to some Blender devs but that they did not decide to include it into the regular Blender build I guess? That's too bad...

- Michael