Wednesday, August 12, 2009

Pump Up the Volume (Renders)

Squeezed in some R&D time for Sinister environments today. The goal was to convey a sense of vastness, best implied with atmospheric perspective. In painting, this is done by desaturating colors for distant objects. In the computer, you need to use volumes, which simulate particulate matter such as dust refracting light through the air, creating a "haze." Volumes are potentially a huge hit on render times. My goal was to find the fastest settings possible to deliver a sense of space and atmosphere.
The parti_volume shader in Mental Ray has always been difficult to understand, but with much trial and error I figured out a thing or two.

First I made some very simple geometry so I could have some "landscape" to light. Since this was a lighting/rendering exercise I didn't want to get caught up in modeling, so I devoted all of 20 minutes to extruding some arches with the "bridge" poly tool in Maya. After trying volume primitives (too hard to make subtle) and environment shaders (too expensive to render) I finally figured out a workable process with the parti_volume shader applied to a surrounding sphere (an atmos-sphere) that produced the above image.
Next I threw some shaders on the geometry. Everything is a variation of the Mental Ray material_x shader:

Next I added some local color and an IBL node for sky illumination (a simple ramp):

Then some bump maps and a warm directional light with cold shadows:

Some model refinements, more lights and turning on final gather:

I guess this exercise pays homage to Roger Dean, since it evokes his "arches" series. But more ... serpentine. This could be album art for a cheesy Yes cover band. Anyway, I figured out some of the esoteric mysteries of Mental Ray volumes. Hope you enjoyed the evolution.

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