Hi Tom,
> they do exist in Blender and can be recalculated / reset in Blender.
Certainly they exist, otherwise it would only do "flat" totally faceted looking shading. But instead of importing the accurate vertex normals from the OBJ file, Blender ignore those and will instead create its own ones by averaging polygon data - this process will usually leave some hint (sometimes strongly) of the polygon structure in the shaded results.
The vertex normals that are stored in the OBJ file come from the original NURBS surface data, and so when those are used for shading it greatly helps the shaded result to look exactly the same as the original surface without any extra work required at all. So because of that I very strongly recommend using a renderer that is able to import and use vertex normals properly, it will generate better quality results with no extra work involved.
Someone could look at Bryce or Thea render for some free rendering choices, and also Carrara and SimLab composer are low cost choices.
Pretty much any other renderer than Blender is able to use the vertex normals properly.
> In addition, there are some modifiers in Blender, "Edge split" that can be used to "break" shared
> normals between two adjacent polygons and give you sharp edges where you need it.
Doing this kind of low level polygon repair can be very labor intensive, particularly for someone who does not happen to have any previous experience in polygon modeling and is just looking for a simple to use rendering solution.
> I usually use the *.LWO to go from Moi to Blender. There is no doubt that it does take a few extra
> steps to "fix and clean" normals from imported geometry compared to other programs but I just wanted
> to let interested folks know that it can be done and blender can be used for high quality rendering.
I think you're grossly underestimating the amount of work and learning involved to do these additional steps - particularly if someone is not experienced in poly modeling in blender you're talking about a big learning curve involved.
Meanwhile with any other renderer that does import vertex normals properly you just import and render and there are no extra steps involved at all.
So I'd still strongly advise not to use Blender if someone's looking for a simple and easy to use rendering solution for rendering CAD data in particular. If you are familiar with poly modeling in Blender, yes it is possible to get some ok results with extra work involved but for a lot of people that's not a very good solution.
- Michael
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