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Ryan Thompson asked ·

How To Soften Geo-Holdout Matte Edges

I'm producing scenes of maya fluid effects reacting to collisions and forces of live-action talent moving through them. The fluid sims are partially driven by roto-animated proxies of the live-talent with collision and motion field properties. Those proxies render as geo holdouts to omit them and what they obstruct from camera, i.e.: we see what's around and in front of them; but not what's behind them.

The approach works, but my loose roto-animation of the proxies reveals minor yet persistent discrepancies between they and their live-action counterparts' edges. I'm able to resolve this by warping the fluid sims' edges in comp, but it's time-consuming.

If I can soften the proxy holdout matte edges it'll mitigate how much work goes into this comp fix, but haven't found a way to do so via MtoA docs, video tuts, etc. Is there a way to either: a) soften geo holdouts' matte edges, b) otherwise soften the proxies matte edges while otherwise retaining holdout features, or c) pipe a facing ratio shader into the holdouts' alpha? If so, please let me know how.

I'm using the MtoA plug bundled in Maya 2018 on OS X.


Ryan Thompson


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