Pyroclastic flow sim, some odd artifacts.

[anupamd]

Guys, just playing around with some fluids stuff and trying to achieve a pyroclastic flow effect. but have some questions for the "pros" out there.

Link to Pyro test

, BUT my question is what is causing this noisey artifact ( you can especially see it near the base and the "leading edge" of the plume).

Here is some info to help debug:

1. Low rez is 100x100x100 uprez is 500x500x500

2. I am using the pyro shader, I am using a noise modifier in the color channel but even with that off I get the strange artifact.

3. I tried various settings for the turbulence in the uprez but still getting the artifact.

4. I tried a version with using the billoweysmoke shader, but if you look carefully you can see the same artifact, its just less apparent because the details are softer.

Link to billowey smoke test

5. To save on disk space, I only exported density field to the highrez cache. Could that be causing issues?

also: the Pyro shader is SOOOO slow... why is that.. any optimization tricks? (buy a faster computer is not an acceptable answer) .... makes me pretty sad.

[anupamd]

I also checked to see if its the depth map shadows, the rat files look clean but who knows. Im using 2 spots, both shadow.

Also tried different volume filters..nothing seems to kill it.

Edited July 7, 2011 by anupamd

[old school]

Could still be shadows or swimming noise in your smoke/ash plume. Is this a low res or an up-res sim?

For the shadows, try rendering a few frames without shadows first.

To see if the noise is causing artefacts, just disable noise in the shader and render a few frames to see.

It's moving way too fast to see what's going on there.

[lukeiamyourfather]

It looks like the sampling and/or resolution of the shadow maps are insufficient. Can you post the shadow settings from the lights?

[bunker]

You're rendering smoke so why do you use the Pyro shader ?

[anupamd]

I started with the billowy smoke preset and then modified from there. But I know what you mean.. its far better to use the right solver for the right task.

I've started to dig deeper into the solver and noticed a lot of wasted data when you are not really using stuff like heat..etc.

I'll probably re-build this setup using a much more lighter weight smokesolver (and even then, there is probably stuff like source/pump that I can rip out).

FYI, I've been using FumeFX in production a lot, and trying houdini to compare for fluids stuff. Everyone complains about houdini's speed, but I think its all in how you set it up.. Im definitely open to more tips on optimizing fluids sums.

Also as an update, the flickering problem was as a result of one of the shadowmapped spotlights having an improper near/far plane.

Also in terms of the shader, for some reason the shader handles rendering of the volumetrics a little better (scattering..etc).

Its definitely slower than billoweysmoke, but has some nice additional features to enhance the look.

I would like to dive into the pyro shader and only steal the stuff i need and add it to the billoweyshader, but I cant seem to dive in to it.. its pre-compiled.

Is there a way to look the internals?

You're rendering smoke so why do you use the Pyro shader ?

Edited July 12, 2011 by anupamd

[static]

I would like to dive into the pyro shader and only steal the stuff i need and add it to the billoweyshader, but I cant seem to dive in to it.. its pre-compiled.

Is there a way to look the internals?

It's written in vex. Hover over the shader, right-click, click Type Properties. Take a look at the Code tab. At least it's a starting point for what you need to add in vops to get what you need.