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Lighting with Atmosphere node


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Hello all,

I'm currently working on a concert simulation and am trying to setup volumetric lighting using the atmosphere node and the advanced renderman smoke shader. I've successfully gotten the atmosphere node to work, my question is whether or not it is possible to choose which lights are affected by the atmosphere node. My scene's center stage has key lights that light up the characters and are animated. I'd like to only have those lights be volumetric, while other misc lights not be affected, but no matter what I do, I can't seem to choose individual lights to be affected. Is this possible and if not, can anyone suggest a work around. Thank you in advance for your help.

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ok so I'm guessing either no one on the forum has done this before, or I'm not being specific enough. My question is really, how do I define a parameter value on a light in houdini. I believe by creating this parameter I should be able to get the shader to read this value and determine if the light i s fog or not. Any help or suggestions are much appreciated.

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from the Help Card:

Light Mask

Space-separated list of names of lights that illuminate this object. You can use wildcards (for example, key_*) and bundle references to specify objects.

You can also use the link editor pane to edit the relationships between lights and objects using a graphical interface.

or am I missing something?

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ok so I'm guessing either no one on the forum has done this before, or I'm not being specific enough. My question is really, how do I define a parameter value on a light in houdini. I believe by creating this parameter I should be able to get the shader to read this value and determine if the light i s fog or not. Any help or suggestions are much appreciated.

Hi CraigS. The illuminance loop that's doing the lighting in your shader takes an optional string parameter called category (in RenderMan, scope in Mantra). You can use this parameter to specify which light or lights contribute to the illumination of your fog.

Check out the section on illuminance loops in whatever RenderMan docs you have.

Good luck dude.

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Thanks Brian. I think I was possibly over thinking. I saw the category space for the light but thought I needed to add an additional parameter from the Renderman 14 set. I'll give it a try using the category.

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Ok, I must still be missing something. I've tried the categories section and adding in user defined options from the R14 set and neither works. I've attached screenshots in case it looks like I'm missing something or entering something incorrectly...

post-4890-1247169487_thumb.png

post-4890-1247169496_thumb.png

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Hi Craig,

I'll put a little example file together when I get in front of a PRman key later tonite.

Long time no see. How're the labz?

I really miss my workstation in the corner of the open lab. <sigh>

Hey Brian,

Thanks. I've started to include Chris R on this too and he seems to think that the category flag isn't working the way it should in Houdini. I'm trying to work around it now or as a last resort, dump the volumetrics. Thanks again for your help though. Hope things are good on the west side.

Craig.

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