> but when I export out to Lightwave the tris tend to pinch the mesh.
Hi Kevin, generally this is caused because LightWave does not support reading in a type of smoothing information called "vertex normals" that are stored in the mesh in OBJ files. These vertex normals actually come directly from the NURBS surface.
In this example: http://moi3d.com/forum/index.php?webtag=MOI&msg=656.16 you can see the difference between doing a rendering with accurate vertex normals and one without. In LightWave you are stuck always without.
You should contact Newtek and ask them to support importing vertex normal information so their renders can get the higher quality look as well. Currently I think that Cinema4D, Maya, and XSI can import vertex normals, so rendering NURBS objects will generally look better in those apps, they won't have that kind of pinching effect.
> <...> why in 2007 we don't have a render that can render nurbs?
It's generally due to speed - rendering the NURBS surface directly requires a tremendous amount more computations than rendering a set of polygons. Even though computers keep getting faster, it is still significant if something takes 100 times as long to calculate.
There are also different problems created by trying to directly render NURBS - it is normal for a NURBS model that has had intersections calculated on it (due to booleans, fillets, etc..) to have different surface pieces that don't touch exactly, instead they touch within a tolerance of like 0.01 or 0.001 units. When creating a mesh, these little tiny gaps are eliminated by creating shared mesh vertices along the common edges. But if you try to render the NURBS surface directly those little tiny cracks can show up, especially if you zoom in a bit.
So that's another reason why meshing is generally preferred.
But the key thing that makes NURBS mesh rendering work really well is having the accurate vertex normal smoothing information. That's the piece that is missing in Lightwave that causes shading problems.
- Michael |
