Pyro stamping

[Hazoc]

I did some little research how copy stamping works for volumes. I used a single 100^3 voxel fire simulation (50 frames) and scattered it onto a spehere with varying scale, rotation etc. This seems very promising. The next task would be making them to react when the sphere starts to move through air insted of just being ridig fire assets living their own life.

First thing that came to my mind is simulating the sphere moving in a volume and using it's velocity field as a lattice control for the small fires to get them related in sops. The question is, can it be done ? Is there a way to deform voxel data in sops ? So that I get flames bending to some direction pointed by a velocity volume.

[Macha]

Very interesting technique Hazoc!

Yes, I think it may be possible in a volume vop. I'll have to think about a little but basically it would be like displacing. You just need the right displacement field but that should be doable. For starters try a noise with very low frequency.

And then merge them all into one volume and do it again!

Edited March 25, 2011 by Macha

[pclaes]

I think someone did a volume along curve deformation as well. You might want to do a search for that.

[dpz]

http://www.sidefx.com/docs/houdini11.0/examples/nodes/sop/attribfromvolume/DeformVolume

[Hazoc]

http://www.sidefx.com/docs/houdini11.0/examples/nodes/sop/attribfromvolume/DeformVolume

But of course! Awesome, thanks.

EDIT:

For this particluar case the sop deform is way too heavy. 100^3 voxels means pretty many points to be deformed times the amount of stamped volume objects. Maybe shader displacement offers a cheap way. This was doable right ? I remember some posts here about volume displacements in shader but can't seem to find right search words. A quick test of creating a displacement shader to simple smoke does nothing.

Edited March 26, 2011 by Hazoc

[sabotage]

Cool good work

[Macha]

Hazoc, displacing volumes is pretty much the same as displacing geometry. I don't have H right now but if I remember well it's just a matter of plugging P into a few nodes (I like anti aliased flow noise usually), and it works well on the sop level. You can also use that nifty use-a-shader-network-in-the-viewport trick to get accurate viewport preview and hires rendering.

Edited March 26, 2011 by Macha

[Hazoc]

Hazoc, displacing volumes is pretty much the same as displacing geometry. I don't have H right now but if I remember well it's just a matter of plugging P into a few nodes (I like anti aliased flow noise usually), and it works well on the sop level. You can also use that nifty use-a-shader-network-in-the-viewport trick to get accurate viewport preview and hires rendering.

I tried various things with no luck. But now I think I found something. And there's a promising looking file from you too, thanks:) Dunno why "volume displacement" as a search word worked now so well:D

[ikarus]

You can also use that nifty use-a-shader-network-in-the-viewport trick to get accurate viewport preview and hires rendering.

you've mentioned that before do you have an example scene explaining this method?

[Macha]

you've mentioned that before do you have an example scene explaining this method?

Off the top of my head, something like this. I think I miss a few steps but I can check next week how exactly it works.

shader.hipnc

[Hazoc]

Off the top of my head, something like this. I think I miss a few steps but I can check next week how exactly it works.

Hmm interesting. What is actually hapening here ? You could modify the volume directly inside the volume VOP with same operators but instead you assign a shop version of them ? You say "to get accurate viewport preview and hires rendering." So it's possible like this to get rendertime volume displacements to show in the viewport ?

[Macha]

Hmm interesting. What is actually hapening here ?

You use a shopnet to calculate both your viewport and your render. So you can stay low-res in the viewport but be hires (mantra volume step size) during rendertime, without loosing precision and detail (you would if you did everything on the sops level and simply use a hires version of it during render). I haven't had enough experience with this to tell you the disadvantages of it (apart from the fact that it doesn't seem to work well on a farm). But I think it is quite interesting and that same option is available in th gas vop in dops I think.

As you can see in this example, the boundary of the object remains "soft" (sop level resolution) and I think that it may be possible circumvent that particular problem somehow.

Edited March 27, 2011 by Macha

[Hazoc]

You use a shopnet to calculate both your viewport and your render. So you can stay low-res in the viewport but be hires (mantra volume step size) during rendertime, without loosing precision and detail (you would if you did everything on the sops level and simply use a hires version of it during render).

Ah, that's handy.

I made a small proto of velocity field displacement in SOPs. Looks pretty good. Next I need to transform this into a pyro shader displacement module.

velocity_lattice.hipnc

[poco]

But of course! Awesome, thanks.

EDIT:

For this particluar case the sop deform is way too heavy. 100^3 voxels means pretty many points to be deformed times the amount of stamped volume objects. Maybe shader displacement offers a cheap way. This was doable right ? I remember some posts here about volume displacements in shader but can't seem to find right search words. A quick test of creating a displacement shader to simple smoke does nothing.

How to make the N vector in sops if i have cached the pyro bego? the volume analysis make the gradient don't help yet~~