( open ) [ PHI-6112 ] foam shader

[ronald_a]

the new foamshader sounds very promising. I can't - however - get anything useful out of it. It either looks a bit off(using approximations) or it freezes houdini when using ray-traced scattering. Would be great to see some simple examples on how to set this up. I would be especially interested in beerfoam.

Thanks in advance.

[pixeltrain]

Hi,
tested it today with a point cloud from a fluid sim. Made some bubbles out of it as foam. Nice reflections, looked great, but a little bit slow
Worked like expected, placed the shader on my point cloud. That's it.
I have used the current nightly build.

Helge

[ronald_a]

pixeltrain thanks for the info. Did you change any particular settings or did you use the default ones? I might also give the latest nightly a chance.

[pixeltrain]

No, not really. I've changed the foam color to grayish and the Mode to "Bubbles". Tested before that the pscale.

[ronald_a]

pixeltrain thanks for the screenshot. I got something that is getting closer to what I want to see (allthough with some changes to the shader). And talking about speed: For me (on a 2 x 20 core machine) the speed is not great. I did try it on a mac (8 core) as well and the same image rendered about two times(!) as fast. So there might be something up with high CPU count or NUMA.

Might be interesting for tsvetomira.girginova to look into.

[tsvetomira.girginova]

Thank you, ronald_a!
I will look at it.

[tsvetomira.girginova]

In conclusion, your observation about CPU count is absolutely correct, ronald_a.
The issue is already opened in the Phoenix FD project.

Thank you both for making our products even better.

Wishing you a wonderful week.

[Svetlin.Nikolov]

Hey guys,

Let me just confirm it's the same thing:
- Are you using Volume Light Cache ON?

If so, can you try this workaround:
- Turn Volume Light Cache OFF and turn Probabilistic Shading ON.

If you have access to the latest V-Houdini nightlies, you better get one too, there are important changes to the Particle Shader there.

Cheers!

[ronald_a]

Hi Svetlin.Nikolov , great you are joining in!

So, yes, I was using Light Cache On.

I did the following tests now:

On a 2 x 20 core machine (windows):

LC ON: 3min6sec (approx&shadow)
PROB ON: 2min8sec (approx&shadow)
PROB ON: FREEZE!!! (raytraced)

On an 8 core machine (Mac, because its the machine with the least cores we have):
LC ON: 1min27sec (approx&shadow)
PROB ON: 1min07sec (approx&shadow)
PROB ON: CRASH!!! (raytraced)


For Probablistic I turned of lightcache in the shader, turned probablistic to always in the shader and turned on probablistic volumetrics on the render rop.

So yes, Probablistic renders a lot faster. But... You should know my rendering (for testpurposes) is only 256x256 with min/max shading set to 1/3 (!). So rendering the same thing in HD with 1/24 will take hours (hence the small resolution, low sampling).

Granted, my testobject might be a bit dense, but it still only has 4.5 million particles.

Attached, please find my testscene (set to the initial settings using lightcache) so you can test for yourself.

Looking forward to your reply.

PS: All this used the latest Houdini production build and the latest nightly.

[Svetlin.Nikolov]

Oh yes, the crash/freeze is a known issue, the fix went in a couple weeks ago, but will ping Andrei so it gets into the VHoudini builds as well.

The speed will be better, but the result will likely be noisier. There should be a couple options in the render rop for adjusting the subdivs - if they are too low, it's gonna be slow, and if they are too high, it's gonna be slow again, so you gotta find a good value in the middle.

Not sure about the option you have on the shader though - I think it's a legacy option that should either do nothing, or be left at the default value.

However, this still does not shine a light on why the speed is different between the different number of cores.

[ronald_a]

Btw. the speed difference starts at the preperation phase for phoenix (the first 2-3 things that happen prior to rendering), so it's not just the actual rendering that takes longer on higher core machines.

It would be great if someone (from chaos) could pick up my testscene or create a new one showing a recommended setup. I feel there are quite a couple of things that can be setup the wrong way (not sure what you mean by "adjusting the subdivs not too low/high" for example)

Maybe this should wait until some things are fix/updated to the latest and greatest.

[Svetlin.Nikolov]

Ah, sorry, I see it's called "samples" in the GUI, not subdivs - I mean the "Num. Samples" and "Num. GI Samples" under the Volumetrics section: https://docs.chaosgroup.com/display/...NI/Options+Tab

Too few samples will render slow, too many will render slow, so the ideal value is somewhere in the middle and it depends on the scene and lightning setup, so there is no easy way for the software to set it automatically.

When it comes to rendering with the particle shader, all of these tips here do apply, so make sure to go through them carefully: https://docs.chaosgroup.com/display/...ering+In-Depth
It's a matter of time until some of this stuff gets simplified and unified with the way V-Ray renders hard surfaces, but for now grid volumes and particle volumes have their peculiarities...

Cheers!