[Radiance-general] splitting a render by light sources - rtcontrib

[Gregory J. Ward]

Hi Will,

The reason you are seeing jagged edges to your spot is because the  
default "direct jitter" or "-dj" setting for rtcontrib is 0.5.  (You  
may discover all the default values by typing "rtcontrib - 
defaults".)  For spotlight's, the edges can be particularly strong,  
and I don't generally recommend this type unless you couple it with a  
light output distribution and set the cut-off past the natural cut- 
off of the fixture -- unless of course you are simply going for an  
artistic effect.

The -u+ option is recommended for rtcontrib, particularly when you  
are using it to render images, because the correlations between  
values will show up in odd ways on a 2-D image that would not be  
noticeable in a 1-D sample sequence.  This is why your original  
rendering looks so odd.

As for the -e option of pfilt, it is used as an additional multiplier  
if auto-exposure is employed with the default -2 (pass) operation, so  
it is not completely overridden.

-Greg

> From: william reynolds <william.reynolds at oriel.ox.ac.uk>
> Date: January 29, 2006 8:45:42 AM PST
>
> hi Greg
>
> theatre.pic is the image with the jagged edges. the optfile is  
> below from my post.
>
> I have also put on another image which I have just generated  
> (t2.pic, the command i generated it with is rtcontib_command, and  
> the opt fiale was theatre.opt), using the -u+ option to rtcontrib.  
> i gather this forces the use of purely mote carlo sampling, with no  
> interpolation (is that right?). this seems to give a better image,  
> but the edges (and indeed the areas in the scene lit entirely by  
> interreflections) are very noisy. I have tried to reduce this by  
> scaling down a large image and applying gaussian filtering to it  
> with pfilt, and although this helps it doesnt really fix the issue.
>
> let me know if there is anything else that i could send you to  
> help, and thanks very much for your help.
>
> regarding the exposure in pfilt - does the auto scaling factor  
> overide a "-e 1" setting? i'm not sure i quite understand the bit  
> in the man page. it doesnt really matter to me, but im curious!
>
> thanks again, will
>