Hi,
Im trying to get the mask of a object that is inside the refracted object.
Is it possible to do in karma? In Redshift only I need to do is set "secondary ray visibility" to "Refraction/transparancy" under AOV setting tab.

Here are some example of renders that i did in Redshit and karma.

Thanks

Hey there,

something seems odd about the images above. Shouldn't the AOVs of the Blue Piggy be… Blue and not a White on Black?
I ask this, because the bottom image shows the volume as colored in the Beauty.

In any case, you may want to read up on LPE — I know, I wish there would be OutOfTheBox 'good ones' on the Karma LOP ROP.

https://www.sidefx.com/docs/houdini/render/lpe.html [www.sidefx.com]
https://lpe-builder.chaosgroup.com/ [lpe-builder.chaosgroup.com]

Here's an example for diffuse light paths.

Re-reading your post, I think Redshift is able to output mattes of certain objects and their light paths. Which is cool — I do not know how I'd do that in Karma. Maybe the devs can say if this is even possible.

Andy_23
Re-reading your post, I think Redshift is able to output mattes of certain objects and their light paths. Which is cool — I do not know how I'd do that in Karma. Maybe the devs can say if this is even possible.

I'm pretty sure it's not possible.

Thanks,
Now i can spend time to find other way instead of spending time on "not possible" things.

I'm also curious why the "beauty" renders in the first image is white on black instead of blue.
For holdout matte, it's not possible with secondary rays since they're part of lighting contributions and not related to pixel coverage. That said you could make a makeshift matte via LPE - for example, writing out all light paths containing objects with certain LPE tag and dividing it by beauty pass in comp.
H20.0 adds 'background' event to LPE so it's possible to write a custom alpha AOV that's based on transmission throughput instead of opacity, which might also serve your needs.

Sure you can do this, this is what LPE's are for . . . Even if they are a bit confusing



Nice docs I used to get anywhere
https://www.sidefx.com/docs/houdini/render/lpe.html [www.sidefx.com]

edit:
I also need to learn to read . . .