[Radiance-general] import from other software

[Thomas Bleicher]

On Sat, May 1, 2010 at 6:37 PM, Jia Hu <hujia06 at gmail.com> wrote:
> For polygon, does the surface normal affect the materials? i.e. the
> sequence of vertex in command Polygon will determine which face
> has the material.

Radiance only uses one material per polygon. Front or back does only
matter if you use a emitting material like 'glow' or 'light' which
only emits to the front side.

> In .obj file, the face with vertex index 1, 2 and 3 and face with vertex
> index 3, 2 and 1 should have opposite normals,  So are the materials added to
> the two surfaces are different.

The front face of a polygon is defined by the right-hand-rule. But
since front and back material are identical it does not really matter.

> ...
> vn 0.000000 0.000000 0.000000
> vn 0.000000 0.000000 0.000000  (this all zeros casue errors when using
> obj2rad)
> ...

That's what I meant about the quality of the *.obj files. You only
need the vertex normals if you want a smoothed surface (for example
for a round column) instead of the faceted polygons. If you can't get
it to work with -f you can just delete all the lines starting with
"vt".


Regards,
Thomas