Monday, March 24, 2014

Ring of Fire

This is fan art for Ring of Fire, a talk show about corporate crime and legalized corruption. It's simply an animated logo with a generic camera path. The animation transitions to a blue placeholder, which is where the talking heads would go.

I used Maya fluid effects (FE) for the fire. I wanted motion blur because it adds another layer of realism. Without it, animation can look choppy and flat. FE are invulnerable to motion blur, so I had to go through a tricky process to achieve it. I'm reporting the process here because I can't find any tutorials that cover it, and maybe this post will benefit someone. (If this helped you, please say "hi" in the comments.)

There's probably a better solution, but this is the simplest one I could devise. It involves creating a mesh approximation of the FE particles from which you can extract motion data to apply within a compositing program (Nuke, Fusion, AE, etc).


step 1: Create your fluid object. Ideally, create a fluid nCache for it.

step 1
step 2: Create a polygonal cube, or any other polygonal object. It doesn't matter which. Set the cube's transform vectors to 0,0,0; 0,0,0; 1,1,1

step 3: Open the connection editor and connect the outMesh property of fluidShape to the inMesh property of cubeShape.

step 3
step 4: In fluidShape attributes, adjust Output Mesh as necessary.

step 4
step 5: In cubeShape attributes, set Mesh Controls > MV Color Set = velocityPV

step 5
step 6: Create separate render layers for the FE fluid and the poly-fluid. For the poly-fluid render layer, activate a velocity element or motion vector pass, depending on which renderer you use.
Be sure to render out as 16 or 32 bit color. 8 bit is insufficient velocity data and may result in crazy blurring.

step 7: After everything is rendered, add the motion blur with your compositing program. Such nodes will be named something like "motion blur" or "vector blur."

motion vector data added to an animation
FYI, for the velocity pass, ...
red = side-to-side motion
green = up/down motion
yellow = diagonal motion

note: The V-Ray renderer is buggy when rendering FE, so I switched to Mental Ray for this project. If you must use V-Ray and it isn't rendering the FE motion data, try rendering directly from the frame buffer or render view with "animation" checked in the VRay Common rendering settings, rather than through batch rendering. Start the rendering sequence on a frame where the FE particles are moving, rather than a frame where they haven't been emitted yet.
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