[Sidefx-houdini-list] rectangular pbr area light

Luc Froehlicher lulu at alamaison.fr
Fri Dec 7 12:03:44 EST 2007


Mario Marengo a écrit :
> On December 7, 2007 09:13 am, Luc Froehlicher wrote:
>   
>> is it possible to have rectangular area light (H9 PBR) ?
>> luc
>>     
>
> If what you want is a *square* area light (not rectangular), then you can use 
> an area light set to "Grid". You can choose among several basic symmetrical 
> shapes with this approach, and it works in every rendering engine.
>   
well I need to mimic kino flo's type of light.
I noticed that if I edit the interface there's a parameter vm_areasize 
in Mantra/Light
(2 floats array) but it doesn't seem to have any influence.
> If you want an actual rectangle, or some other arbitrary shape, then create 
> the emitter geometry and assign it a constant shader (vex_constant will do), 
> then make sure your ROP's "Diffuse Limit" is set to 1 or higher, else you 
> won't get a diffuse contribution (Glossy Limit defaults to 1 I believe, so 
> you'll get one bounce of specular, but no diffuse, by default).
> Anyway, I guess the main point is: assigning a constant value (as opposed to 
> bsdf) to the global F in a shader is equivalent to defining an emitter with 
> the given value as its power.
> Also, you'll likely need to raise "Pixel Samples" in the ROP to something 
> higher than default to reduce sampling noise.
>   
I tried that and increased the diffuse value but , as you say , it's 
very noisy :(
thanks for helping.
luc
>
>   





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