Matting / holdout options with feather radius for volume grid?

[joconnell]

Heya folks!

At the minute I'm doing a load of breath sims in fume just emitting from particles. As usual with fume, the source emission area looks a bit crappy and since we're trying to do breath, you shouldn't see the place it comes from. We sim to fxd so we can try the volume grid for rendering and what could be really handy for us is if you could use a matte / holdout object to cut down the opacity of certain cells of the grid and if there was some kind of feather / fadeoff distance option for each of the holdout objects. I tried to use things like a gradient ramp as a mask and even a distance tex but no joy. Any thoughts on if this'd be possible?

[super gnu]

if you are using textures with the volumegrid, you should get one of the latest builds, as i believe the objectspace mapping for the volumegrid is still borked in the official versions.

having said that i dont believe this should affect distancetex.. have you tried using it as a modulating texture for the smoke opacity?

[super gnu]

bear in mind that using any procedural textures to modify a volumegrid tends to bump up rendertimes a fair bit.

[kagemaru]

I reckon you already tried the cutter geometry right?
It does what you're asking, though it doesn't have a feather option that i agree would be excellent.

[joconnell]

Yeah even a regular matte object works on it - just having the option of a soft fadeoff on top of it!