Re: I don't want an elliptic sun.... (advanced patch placement in 3d)

[Christian W. <cwa...@gm...>]

Andrea Viarengo wrote:
> I was not able to put a patch so that it is always orthogonal to the 
> segment connecting the center view (nx,ny,nz=0,0,0) with its center.

I haven't had a chance to look at your code yet - I'll get to that 
shortly - but I wanted to mention the following right away:

> (You know that in the reality the sun is a sphere, 
> so it should always appear circular from anywhere I look at it, 
> and never should be appear elliptical ...)

No. That's not true. Projecting a sphere onto a plane will not get you a 
circle unless the projection direction is perpendicular to the plane 
(i.e., you're looking straight at the sun, so that, for a non-skewed 
camera, it is in the center of the image). Think about it!

(The same thing said a bit more verbosely: 
<http://tag.povray.org/povQandT/misconceptions.html#perspectivespheres>.)

  -Christian