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Subject: Re: Basic perspective/normal q



[jongware] wrote:

> What I've done sofar is: transform points with a matrix. Transform normal
> vector with same. Test if it is visible;

You can't test visibility of a plane from nothing but its normal
vector. You *need* the 4th parameter, 'd', or a reference point.
E.g. there could be two parallel planes, orthogonal to the camera's
"z" axis, with the camera in between. One would thus be fully
visible, the other not at all.

Your impression that the perspective transformation has anything to do
with this is wrong. Perspective doesn't affect visibility of a plane.

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

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