upres at render

[Hello world]

is it possible to simulate in a lowres and increase the voxels at the render time using delayed load shader? what could be the approach for this

[Annon]

They will be upscaled at rendertime by mantra. You'll want to add noise to it to get any more detail out.

Probably not the best idea though, just upres your sim.

[Skybar]

A voxel is just a 3d pixel, so if you think of it like a 2d image you wouldn't get any more detail out of it by just increasing the number of pixels. The initial data is all you have. So if you have a 128x128 image and scale it up to 1024x1024 it will be very pixelated for example. You can smooth it sure, but it won't get more detailed.

[Netvudu]

This is what the "up-res container" tool was born for, isn´t it?

Edited March 27, 2014 by Netvudu

[Guest tar]

yes and no, you can use a delayed load shader to load in higher-res simulated simulation but you have to do the simulation before, not at, the render time.

[Filipp Elizarov]

One approach is to create a cvex shader with gridless advection at render time.Rhythm and Hues has published a few papers about this tehcnique.You can implement it into the shader with inline code or in cvex shader as well.

Edited March 27, 2014 by Filipp Elizarov

[Netvudu]

One approach is to create a cvex shader with gridless advection at render time.Rhythm and Hues has published a few papers about this tehcnique.You can implement it into the shader with inline code or in cvex shader as well.

wow, that sounds as cool as complex

Edited March 27, 2014 by Netvudu

[Annon]

It's not complex if you can use the volumeVOP, same thing.

Getting the noise to stick however can cause issues. You have to output rest and rest2, blend between them etc, get stretching blah blah.

I've had some decent results with it in the past to get pyroclastic noise to stick to a lower res sim, but in the end I always end up just doing a high res sim (or at least upresing a low one).

 

If you want whispy smoke then gridless advection would work.

https://vimeo.com/54646735

 

CVEX noise for anything else. But honestly, best bet is to get a good sim.

C

[Jordan Walsh]

If you want whispy smoke then gridless advection would work.

https://vimeo.com/54646735

 

 

What was the technique to getting that working in houdini?

[Annon]

Gridless advection...

There's posts about it on here, do a search.

[Jordan Walsh]

Gridless advection...

There's posts about it on here, do a search.

 

Yeah, I was following that thread a while ago. Some interesting results but not much talk on how anything was done. I've been looking at getting detail in to volumes at render time using cvex but render times go out the window very quickly. Ive been looking into rebuilding something like the cloud noise in a shader but not sure exactly how to go about it. I have tried it in a volume procedural and it works great but you get pretty noisy renders and there are no filtering options like standard volume rendering.

[fxrod]

How does gridless advection work compared to using noise in the pyro shader? Seems like you'd be advecting noise on a lo-res grid either way...

[teratera]

I'd really like to give it a try too (Gridless Advection technique), but can't understand what to do at the very basics. For example, how do I even advect a scalar field with velocity using VOPs or VEX? Would really appreciate any clues, thanks.

[Jordan Walsh]

You would do it at render time with a vex volume procedural geometry shader. In the CVEX shader you can use a volumesamplevfile node to sample your density at the position minus your velocity (needs to be minus as you are specifying where to sameple for that position, not "pushing" the volume to a new position).

Thats a pretty simple example, but I dont know how gridless advection would be implemented in this way.