ChukermanI'm not that familiar with RS, but I thought you have to turn on Refraction Affects Alpha Channel setting on for it to behave that way, which is the propagated alpha I mentioned, to fake the transparency for refractive surfaces
Try to render glass cube via redshift, and will see right alpha channel, I mean
jsmack
I'd rather Houdini's native renderer not normalize such a non-physical hack that's incorrect by design.
tamtejsmack
I'd rather Houdini's native renderer not normalize such a non-physical hack that's incorrect by design.
If implemented elegantly I'd welcome it, since it has its uses especially for thin wall objects where the non-physicality can be marginal enough to be acceptable
but more general AOV propagation through lightpaths at least refractions is very necessary
the Alpha propagation or at least mask could probably be done using LPE's if houdini LPEs supported background token B like some other renderers do
jsmack
However, I don't want to see a simple 'transparency alpha' option, as the messaging is misleading as it legitimizes using it as such.
briansjsmack
However, I don't want to see a simple 'transparency alpha' option, as the messaging is misleading as it legitimizes using it as such.
how about...
- a geometry property "refraction as alpha"?
- defaults to off
- when on, for paths that travel only through refractive bounces and then exit the scene, we track the final contribution, and then output that to alpha.
or does that still irk you John?
Jonathan de BlokHow would you approach this?
Haven't tried but chances are you can get it using a cryptomatte output. Should be good enough for comping when refraction is not that relevant.
brians
It's a feature that exists in Redshift that people have requested a few times now.
I'm no expert on its behavior or use, but my guess is they'll be using a dome light that somewhat matches the backing plate.
dleeCan you post a visual example of this?
Hi. As of Houdini 20.0 karma supports 'B' (background) event in LPE so you can describe any light path to uses as custom alpha (which then you would invert in comp).
For example, if you want to consider any background hits with 0 or more transmissions, use 'CT*B'.
dlee
Hi. As of Houdini 20.0 karma supports 'B' (background) event in LPE so you can describe any light path to uses as custom alpha (which then you would invert in comp).
For example, if you want to consider any background hits with 0 or more transmissions, use 'CT*B'.
coccosoids
Can you post a visual example of this?
dleecoccosoids
Can you post a visual example of this?
Of course, here's a screencap of the parameter window showing the LPE set up and its output. Note that karma does not support 'negate' operation in LPE, so you'd negate it in comp should you need it.Image Not Found
dleecoccosoids
Can you post a visual example of this?
Of course, here's a screencap of the parameter window showing the LPE set up and its output. Note that karma does not support 'negate' operation in LPE, so you'd negate it in comp should you need it.Image Not Found