> This has been done
> before, and is actually slower on modern systems (there was a thread
> about it recently on comp.graphics.rendering.raytracing). You go through
> a lot of contortions to get it to work, and get a more limited, lower
> quality, slower renderer as a result. Now do you see why?

Hmmm...

To be sure, I downloaded Tachyon and built
double- and single-precision DOS versions and put
them to the test. The results (in seconds,
on a 633 Mhz Celeron):

island (an hf with reflecting water):
  44.131 DP vs. 32.903 SP

teapot (specular material with reflecting plane):
  12.898 DP vs. 9.993 SP

820spheres (a flat but shadowed sphereflake):
  18.135 DP vs. 13.971 SP


I also checked the images to test quality, but found
no discernable difference. No gaps, nothing.

Perhaps the raw computation time for double precision
is as good as or better than single precision, but
the memory latency is lower since half as much
numeric data is being referenced. Well, whatever it
is, there's a difference in favor of SP. I'm going
to try it later today on a modern box which has
a much faster memory bus as well, just to be sure.

As for the primitives, yeah, Tachyon doesn't
have the complex ones, but if it has enough,
and one can get SIMD or GPU assist in the bargain,
then that's not a bad little raytracer for some projects.
I wouldn't mind having a "turbo option" for simple
scenes in POV-Ray.

Ray

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