[Radiance-general] rtcontrib and ambient cache

[Gregory J. Ward]

Hi Rob,

Glad to have some eager beavers going at this...

> However, when I run
> the command:
>
> vwrays -ff -x 1024 -y 1024 -vf best.vf | rtcontrib -ffc \
>          `vwrays -d -x 1024 -y 1024 -vf best.vf` @render.opt \
>           -o c_%s.pic -m light1 -m light2 scene.oct
>
> I get the following message:
> rtrace warning: zero ambient accuracy so "test.amb" not opened
>
> ...but I did have -aa set to .1 (and this is in my render.opt  
> file), and
> there is a valid ambient cache.
>
> Two questions:
> a) Why is this happening?

The -oTW option of rtrace (used by rtcontrib) doesn't work with the  
ambient cache, because information would be lost in figuring ray  
contributions.  Therefore, rtcontrib sets -aa 0 to switch caching off  
in its call to rtrace.  You should adjust your -ad value  
accordingly.  (It also sets -as 0 for similar reasons.)

> b) Is this the only reason for the direct-only component showing up  
> in the
> renderings, or is this the intended result of the command?  IOW, I was
> hoping to be able to create renderings that showed the net result of a
> single light source, but both its direct *and* indirect  
> contributions to
> the scene. Can this be done?

Yes, you should see both direct and indirect contributions from  
rtcontrib.  At least, that's the idea.  Maybe I should check to make  
sure of the results, because my test scene didn't contain much  
indirect lighting.  Let me get back to you on this....

-Greg