Rendering large space with small detail (small picture now attached!)

Great follow-ups Jack. A couple of points within...

If this is the case and all the geometry is black, then you can

xform -I original_geometry.rad > original_geometry.flipped.rad

This will flip the orientation of all the normals in

Cool, all these years I never noticed that option to xform. The cool thing
about Radiance is you never will know everything about it.

What we really need is some kind of program to re-orient normals based on
some point. I thought I had an old AutoLISP routine that did that, but
man, that is long since gone from my backups (both the DVD kind and the
grey matter kind)!

In Autocad (for example) 3dfaces that
are built in a clockwise manner will have the normal pointing out of
the clockwise face (I hope I am remembering this correctly).

It's hard to tell from your description if you are or not. Think of it
this way: let's say you are drawing a polygon that represents the face
(screen) of the computer monitor you are now staring at. If you draw the
points in a clockwise fashion, the surface normal will be pointing away
from you (out the back of the monitor). If you define it with points in a
COUNTER-clockwise fashion, the polygon's surface normal will be pointing
at you. IOW, in the first example, with a glow applied, the monitor face
would render black. In the latter example, the monitor face would glow.

This can be reinforced by a permutation of the so-called "right hand
rule". Take your right hand and point at your face with your thumb, and
then curve your fingers around the axis defined by your thumb; if you
imagine your fingers pointing in the direction of rotation (and direction
of point creation), your thumb describes the surface normal (vector).


On Thu, May 28, 2009 7:50 am, Jack de Valpine wrote:

Rob Guglielmetti