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View Full Version : final gather with area lights or surface shader


charliedz
05-14-2009, 04:08 PM
hello all,

so if im doing a relatively common lighting setup for product visualisation, i read that final gather is faster and usually sufficient in quality.

i learned FG with the use of a dome sphere engrossing the scene set to a white surface shader.

what about the use of area lights or any other lights with FG or is FG mainly for using with shaders as materials.

thanks in advance for any clarification.

thanks!

djx
05-15-2009, 02:52 PM
I would use both. Adding some direct illumination (area lights) to a scene with mainly indirect illumination (FG) can end up looking cleaner than FG alone, but it will probably take longer to render.

I use polyMesh planes with the mia_lightSurface shader, for FG source and reflections. I use these like those huge diffuse light boxes. Then relatively small area lights, with a physicalLight shader, are added as key lights, especially when more well defined shadows are required.

I've used domes with HDR image maps too (very quick renders), but I still prefer the flexibility of the lights and lightSurface shaders because I can move them around and scale them as I please.

-- David

Dangertaz
05-18-2009, 08:08 PM
DJX,


What settings within the mia_light_surface to you like to use for your reflectors? Do you set them to use lights? Refl Contrib to 1.00? Are you turning specular and diffuse off in your smaller area lights so they're only casting the shadows and nothing else?

Thanks

djx
05-19-2009, 01:48 AM
I'm trying different things all the time, but what I tend to do is use the polys with mia_lightsurface as reflectors, because they give a cleaner reflection that what you get with a visible area light. I like using mia_lightsurface because you can independantly balance the reflection and final gather contribution.

At the moment I'm using a rig where I hide my visible area light behind the poly surface (the poly is set to not cast shadows). Then in the mia_material_x I leave checked the "no highlights for visibile area lights" attribute.

So the polys/mia_lightSurface gets used for reflections and a bit of additional FG when needed, and the area lights create the direct illumination and shadows.

-- David

wizlon
05-19-2009, 12:45 PM
At the moment I'm using a rig where I hide my visible area light behind the poly surface (the poly is set to not cast shadows). Then in the mia_material_x I leave checked the "no highlights for visibile area lights" attribute.

-- David

Or you could just turn specular balance on your mia material to 0 if you don't want highlights.

djx
05-19-2009, 01:22 PM
Yes, that would be better I think. Thanks for the tip.

-- David

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