Rob Sullivan

robsdesign

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Houdini grooming length interpolation Oct. 9, 2022, 3:21 a.m.

There are a few methods that might work:

1) Paint some attributes onto the skin and use them to alter the front hair.
2) Paint some attributes onto the skin and use clumping.
3) Use more guide hairs and alter the influence radius.
4) Combine any of the above (ie. Paint an influence radius attribute on the skin)

Notes:
Attributes can be used like masks to separate guide processes on specific parts of the hair.
Adding guide hairs before a groom will probably break it so you may want to try Reguide after your groom instead.

Hide object but leave reflections Sept. 22, 2022, 7:14 a.m.

It's been a while since I've used Mantra so I haven't looked at the updated workflows for this. ie. Last time I checked, it was done using Extra Image Planes on the Mantra ROP but after a quick search, I can see the following;

https://www.sidefx.com/docs/houdini/nodes/lop/backgroundplate.html [www.sidefx.com]
https://www.sidefx.com/docs/houdini/gallery/shop/vopmaterial/shadowMatte.html [www.sidefx.com]

Not sure if there is a non-Karma version of the first link but that looks like the more recent workflow.

Hide object but leave reflections Sept. 21, 2022, 5:12 a.m.

If you are using Mantra: Go to the render tab on the fire geometry. On Render Visibility, either type -primary or use the drop down "Invisible to Primary Rays (Phantom)"
If you are using Redshift: Go to Redshift OBJ>Visibility tab on the fire geometry and uncheck "Primary Ray Visible".
If you are using something else: I don't know.