Volume rendering particles?

[Guest ravin]

Hi,

I want to volume render particles as clouds and dust with self shadowing and scattering. Any ideas?

thanks,

[Macha]

Well, if you insist on scattering then I'd say try the pyroshader with volumes.

If it is just particles you're after you could try and calculate the amount of particles in each particle's proximity and base a pbr light emission parameter on it.

particle.hipnc

Edited July 16, 2010 by Macha

[bunker]

you can do a pointcloud lookup in a smoke shader to transfer density from points to an empty volume

and use the "volume bake" sop for scattering : it gives you 3 colour fields : Cd.x,Cd.y,Cd.z

Hi,

I want to volume render particles as clouds and dust with self shadowing and scattering. Any ideas?

thanks,

[Macha]

Hey Julien, that's very interesting. I didn't know about that before. Do you mean something like this?

scatter.hipnc

[Macha]

screenshot.

If you look at the Cd values, the scattering seems to be almost exactly isotropic and I don't seem to be able to control that effect much. Is that expected or did I make a mistake in the setup?

Edited July 19, 2010 by Macha

[bunker]

Hey Macha,

what I really meant was that :

- create an empty lowres volume

- add the density from point cloud ( in a volume vop, pcopen/pcfilter )

- use the volume bake to create shadows and scattering

- now create a hires empty volume

- merge it with the Cd.x,Cd.y,Cd.z from the volume bake

- in the volume shader, lookup a bgeo file with the points to re-create hires density

( that allows to mix lowres shadows+scattering with hires density )

- the trick is the transform in the shader ( in blue )

have a look

points_to_clouds.hipnc

[bunker]

That's a bit better ...

points_to_clouds2.hipnc

you should also have a look at the "meta-loop Import", it works with metaballs :

http://www.sidefx.com/docs/houdini9.5/nodes/vop/metaimport

http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&p=9110

Edited July 19, 2010 by bunker

[ikarus]

i happen to puts around with particles to volumes the other day and i have this method, its rather straight forward though i think bunker's solution is cleaner, probably want to integrate his ideas into mine eventually

basically i had a low res fluid sim advect a POPnet with the same emitter, then the point density is calculated through a PC iterator; i also multiply it based on the life of the particle. then i have a volume based on the bbox of the particles, and density is picked up through a pc loop, though ive seen nice results from meta-loops which i might add later.

particle_to_volume.hipnc