I can't be sure that the error is due to Megapov but that's what is running
when the error happens.

The error is:
Illegal grid value in dda_traversal().

I am using radiosity and photon mapping.

What am I doing that might be causing the error?  The image still renders,
but I feel I should try to resolve the error, however it gives no line
number and the error seems cryptic to me. I don't get any other warnings or
errors.

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That's an old height-field problem that has been part of POV-Ray for years
(long before MegaPov entered the scene).  It is caused (AFAIK) by
floating-point precision problems, where a ray "leaks" through the
height-field, causing the height-field intersection algorithm to get very
confused.  A workaround is to move your camera a very small amount (just a
fraction of a unit in one direction should be sufficient).

-Nathan

"Patrick Dugan" <pat### [at] netinsnet> wrote...
> I can't be sure that the error is due to Megapov but that's what is
running
> when the error happens.
>
> The error is:
> Illegal grid value in dda_traversal().
>
> I am using radiosity and photon mapping.
>
> What am I doing that might be causing the error?  The image still renders,
> but I feel I should try to resolve the error, however it gives no line
> number and the error seems cryptic to me. I don't get any other warnings
or
> errors.

Post a reply to this message

Patrick Dugan wrote:
> 
> I can't be sure that the error is due to Megapov but that's what is running
> when the error happens.
> 
> The error is:
> Illegal grid value in dda_traversal().

Time to refer to the VFAQ -
http://www.students.tut.fi/~warp/povVFAQ/miscVFAQ.html#ddatraversal

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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