lewis_T
There is no workaround. Whitewater is best done as rasterized volume with spec layer on top
that uses the gradient of volume. There are only three engines that support this workflow, two of them
are public. Mantra and 3Delight. Hyperion at Disney supports this, and I'm pretty sure prman internally
at ILM does.

This really needs to be addressed, as feeding volumes is much faster to render. The Mantra method still required the
presence of the gradient SDF, 3Delight will create the gradient SDF on the fly if it's not present, it also supports
frustum volumes.

I think Karma XPU needs to support using the gradient SDF as a Normal for the spec layer which is layered on top of
the volume. It's the default method we use in Studios to render White Water for several years now, and if Karma is the replacement to Mantra it needs to have feature parity with a core VFX element render.


L

Agreed+ thank you for the detailed info. Hopefully people at SideFX see this

I wrote a blog post - https://www.arctiem.com/post/creating-multiple-material-slots-in-unreal-using-houdini-engine-hda [www.arctiem.com] specifically about this problem. Let me know if it helps!

Apologies for not checking this thread, where I asked the original question.

Currently (Houdini 20 latest build), I don't see the whitewater shader with the PBR node working in Karma XPU. It does, however, work in Karma CPU.

In my opinion, it's a missed opportunity not to have added this feature in the new release of Houdini from 19.5, but it may be something SideFX can consider introducing soon. It would be nice to have the speed and flexibility of using XPU when rendering whitewater because it is one of the most time-consuming renders there is.

Another feature request would be to have the ability to render line primitives with width in XPU. It currently works on the CPU but doesn't work on XPU.

If someone finds a workaround for using the whitewater shader in XPU, please post how you did it!

https://www.arctiem.com [www.arctiem.com]

Hey guys, I'm trying to set up a whitewater shader to render my ww inside of Karma XPU since Karma CPU is taking too long, as I have over 20 million ww particles. The pyro shader works pretty well as a uniform volume shader, but I can't get the reflections you get from the default ww shader that has the PBR reflect node. Has anyone had any experience setting up the reflectivity node inside materialX? Or maybe a workaround?

Rendered completely in Maxon Redshift and Side FX Houdini, comped in NukeX.