[Radiance-general] Slow rendering with transparant textures

[Greg Ward]

Hi Iebele,

One of the slowest things in Radiance is the .cal file evaluations,  
so minimizing expression evaluations is the key to faster renderings  
in this case.  Having many surfaces for each ray, all having function  
evaluations, is bound to be slow.  Combining or eliminating such  
calls would help a lot.  I don't know enough about your situation to  
recommend "how."

-Greg

> From: "iebele" <info at iebele.nl>
> Date: July 27, 2008 11:27:29 PM BDT
>
> Hi all,
>
> I have a model with about 40.000 polygons, each textured with a  
> mostly transparant image (only about 1% of the texture is visable).  
> Seen from the rendering viewpoint the polygons in the model overlap  
> quite a lot, so one ray might have to "look" through about 50  
> "transparant" polygons or even more before actually "see"  
> something. I think this is why this particular model renders  
> amazingly slow, even with -ab set to 0, -st 0 and -lr 1. Is there  
> another parameter in control that might speed up the rendering in  
> such case?
>
> -Iebele