How to render sharp, crystal clear volumes?

[magneto]

Hi,

 

Volume renders always seem to have a gaussian blur look to them which might be useful for most cases but I want to get a very sharp volume render. For example this image is out of SESI help:

 

https://www.sidefx.com/docs/houdini13.0/examples/out

 

 

Is it possible to render this image so it looks really sharp, crystal clear? As if the balls are not made up of fog? I want a fog like behaviour but very sharp look.

 

I assume this is to do with shaders than rendering parameters but I tried this advice in the thread below but didn't get a crisp render:

 

http://forums.odforce.net/topic/11334-create-edgy-smoke/#entry72510

 

I would appreciate a simple example if it's not too much trouble.

 

 

Thanks

[Skybar]

Higher density on the shader, and a higher Volume Quality on your Mantra ROP might help. 

 

Quick test increasing those two:

[magneto]

Thanks David. When you increase density in the shader, do you just multiply it with an arbitrary number? I thought it clamps at 1?

 

Also what kind of volume quality values are you using? I assume 1 is very low, right?

[Skybar]

I just increase it to whatever looks fine on the shader (basic smoke), you have a shadow density there as well. It doesn't clamp at 1, I've used values over 500k at times.

 

The default Volume Quality is 0.25, which is a ray march of 4 voxels. A value of 1 uses the native volume resolution, ie a ray march of 1 voxel. 2 is 0.5 voxels and so on. Depending on the scene this can be a very expensive setting though, however in this example scene I could set it to 10 without an issue - I don't know if that is because it uses metaballs as a volume. 

[pbarua]

For sharper and brighter look you can also use volume light.

Use existing volumes for volumelight itself.

 

cloudlight rig is also an option. 

[koen]

I think that image is pretty old as well. The default for the volume filter used to be gausssian. Recently the default changed to box width a width of 1. That made all the volumes appear a lot sharper. (these setting live on the geo object under render->shading by default).

 

Cheers,

Koen

 

[dulo]

I guess something like sdf surface rendering in 3dcoat would be the way to go .. 

else you would have to have insanely highres volumes .. 

[koen]

Not exactly sure what you mean dulo, but if you mean rendering the iso surface from an sdf, you can do that in mantra as well (but you'll be rendering a surface, not a volume, so I am not sure it answers the question posted here.)

 

fromm http://www.sidefx.com/docs/houdini13.0/props/mantra

 

Volume isosurface Houdini name vm_volumeiso

Rather than generating samples inside a volume, this setting will configure the renderer so that it automatically finds an isosurface of the volume density field and renders this as a surface. The vm_volumedensity parameter is used as a threshold to control the isosurface density threshold. You should use an ordinary surface shader when rendering volumes with this setting enabled - not a volume rendering surface shader.

By default, the isosurface is found by ray marching through the volume to find points where the threshold density is crossed. This means that to improve render accuracy, you can increase the vm_volumequality parameter. Some volume types use a native accelerated isosurface search technique in which case the volume quality is ignored and the isosurface is determined analytically for that particular type of volume. VDB volumes, for example, use this analytic isosurface rendering approach. The vm_volumeisodefault parameter can be used to disable this native intersection algorithm.

[dulo]

Interesting. I really didn't know about this option.Does it generate intermediate polygons or does it really render the isosurface? Thanks for the tip !

[edward]

It does not generate polygons