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]

Hi guys !

I've read the topic and I'm looking too to find a way to add specular layer on a Karma Pyro Smoke Material

Does someone know how to do it at this time please ?


I'm running on Karma CPU, the legacy whitewater shader works well but I prefer the Karma's Pyro shader look


Thanks you in advance to all ! (:

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

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

As a workaround we rendered two passes.. volume and spec on a meshed volume then combined it in nuke. Worked ok.
Looking forward to a proper Sidefx implementation.

Can I ask a begginer question？
What is the best way to render whithewater in Karma CPU in H20?

What it worked for me, but I didn't have the exact foam result, is to turn points into volumes and control their size (widths) with a wrangle inside de solaris.

I also used the legacy preset from vex shader builder, but I can't control exactly the opacity like the principle shader does. For me, this almost gave me the artistic result, but I feel something is still missing.

Any updates on functioning whitewater shader with easy spec inside Solaris on H20.5?

mzigaib
Any updates on functioning whitewater shader with easy spec inside Solaris on H20.5?

There is no solution, if you are looking to use Karma.
You can either use the old Mantra VOP way > Karma CPU and it sort-of works, but not really.
If you are in XPU, you are locked to MtlX and it has no support for sampling an SDF gradient to feed
a spec lobe that would go into a MtlX layer or MtlX add.

I can't see the MtlX committee agreeing on SDF gradients/volume sampling just yet, I mean we don't even
have bezier ramps in the official distro.

I think, as sidefx is already deviating from strict MtlX nodes to offer some Karma-centric ones, they
could look into SDF/volume lookup support, whether that requires work on Karma itself too who knows.

Personally, I would use 3Delight, I am biased but it's the only off the shelf engine that supports spec
on volumes, it doesn't even require an SDF gradient, it makes one on the fly for you.

L

Thanks for the feedback

Yeah I am aware of the lack of support of this issue which BTW was what made Houdini Mantra a go to for whitewater solution, I am sure that Sidefx is aware of this problem but for now it is kind of disappointing not have it, and go for Mantra now that everything is moving to Solaris and USD is not a option.

My solution for now is to render a second pass with spec in Karma but it is really not ideal and it is really hard to get it right imho and it is kind of hard to convince your studio head of IT to use another render engine just because one specific issue, maybe it is a matter of Sidefx to know that this needs attention and I hope they see this.

mzigaib
...a matter of Sidefx to know that this needs attention and I hope they see this.

No need to 'hope'. Please take 5 mins to fill in the form - with links to this thread and as above. Then they will see it - and we might see some action.

www.sidefx.com/bugs/submit [www.sidefx.com]

Done.