Kenneth <kdw### [at] earthlinknet> wrote:
> > 1) A sphere makes the rendering slower...
> >    A sky_sphere doesn't need to be traced, and if it suffices, it eliminates
> >    the useless overhead.

> Interesting. I didn't know that.

  Even if sky_sphere had to be traced, it would only have to be traced for
rays which don't hit anything in the scene, so it would still be more
efficient.

  However, as I said, it doesn't even need to be traced. What POV-Ray does
is that when a ray doesn't hit anything, and there's a sky_sphere pigment
defined, it calculates the gradients of the ray and picks up a color from
the pigment as a function of those gradients.

  The effect is the same is if the sky_sphere was a unit sphere (with the
specified texture) centered at the starting point of the ray which doesn't
hit anything in the scene. But without the need to actually create and
trace such a sphere.

-- 
                                                          - Warp

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