[Sidefx-houdini-list] rectangular pbr area light

steven ong steve_nong at pointy.tv
Fri Dec 7 12:21:33 EST 2007

Maybe a different way to set it up will be to put two square area lights 
together to create the rectangle?


Luc Froehlicher wrote:
> 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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