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Subject: Re: Basic perspective/normal q



[jongware] wrote:
> I'm still struggling with this basic 3d stuff!
> I have a 3d rotation matrix, a set of planes, and a couple of normals
> associated with these planes. To draw a plane I rotate the associated normal
> and test if its z is positive (right-handed AFAIK). If so, the plane is
> visible and should be drawn.

That test is wrong. You have to test not only the normal vector, but
also the position of the plane along that normal, to know if it's
visible. A plane can very well be completely behind the camera, and
still have it'z normal.z be positive.


--
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

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