Drew wrote:
Thanks for the info.
FWIW, it probably doesn't have to be that way. The shading 'math', as
you put it, should already be a function of the observer's position,
in which case some conditional logic might take care of that.
I might try to find the code for this. In the meantime, I'll just
draw two opposite single-sided surfaces.
In opengl, lighting/shading is entirely dependent on the normal you
define for each vertex. The orientation of the surface does not factor
in. The orientation is used for backface culling, but that's something
entirely different.
Think about a terrain surface for instance, where the "normal" at any
given point needs to be some average of the normals of the surrounding
faces ... perhaps weighted by face size. If opengl decided to be smart
and overrule what you've provided for a normal, you wouldn't have the
level of control you need to do a lot of things.
Curt.
--
Curtis Olson http://www.flightgear.org/~curt
HumanFIRST Program http://www.humanfirst.umn.edu/
FlightGear Project http://www.flightgear.org
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