> CLipka's Radiosity Voodoo recommends that pretrace_start be a power of 2
> multiple of pretrace_end, and that pretrace_end translate to one pixel.
> Calculating the pixel size is easy enough, but deriving a good pretrace_start
> from that over various image sizes requires real math, so I incorporated a
> formula into one of my include files so I wouldn't have to figure it out each
> time.
>
> Last night, I decided to extract this into a stand-alone macro.  Breathe easy;
> it allows you to ease up on the pretrace_end recommendation.  I hope you find it
> useful.
>

The formulas are prety simple:

pretrace_end 1/image_width // stop at 1 pixel block
pretrace_start 64/image_width // start with 64 pixels blocks

Those will have the pretrace start at 64 pixels and end at 1 pixel 
blocks for any resolution for a total of 7 pretrace steps.

image_hight is unimportant and must be ignored. The size of the pretrace 
tiles is strictly a fraction of the horizontal image of your image.


Alain

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