Great terrain tools, but without atmosphere the furthest terrain looks as clear as the closest, no feeling of distane, of air, of haze and fog, how do i get atmosphere in houdini?
In Vue and Terragen, it’s there by default. In Clarisse, it’s done with. Volume box, amd houdini?

In Houdini it's done by reading atmospheric rendering/simulation research papers, and trying to figure out how to implement it in a mantra shader.

What he's saying in a bit of a glib manner is that there isn't anything by default in Houdini, and it has to be built into the shader.

lookdev
i have noticed an arrogance in some older houdini users. Is this how you welcome new houdini users? Is this what the Houdini community stands for?

Don't take it personally. He was more taking a joking jab at us for not having an easier way, because ideally, there would be something built-in to make it easy. I think he agrees that there should be an easier way and was just being sarcastic, while possibly pointing out something he's actually had to go through to get it to work in production.

If you just want a uniform volume, you can create one fairly easily with a Volume SOP [www.sidefx.com] in its own Geometry object. The first component of the Initial Value parameter will be the density of the volume. You can use the bbox expression function [www.sidefx.com] to reference the size and centre of the heightfield, if it might be changing, or you can just type in the size and centre.

If you want something fancier with clouds, there are various tutorials online about how to make clouds in Houdini with the VDB tools.

Hopefully some of that was helpful.

It's not really a joke, just an unfortunate reality when a non-trivial feature is missing. Some have requested this feature, and a few have dared to try to implement it. Maybe a generous veteran would be willing to share their mantra implementation.

https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter16.html [developer.nvidia.com]

https://www.alanzucconi.com/2017/10/10/atmospheric-scattering-7/ [www.alanzucconi.com]

I really do hope that an upcoming Mantra GPU (or whatever code-name SESI gives it) will be able to implement render-time atmospheric effects. Once you get used to Redshift and Octane, it's hard to go back to any other way.

Or maybe one could ‘fake’ it, by taking a painters approach.

Maybe I'm a bit naive…but at some point I was going to give it a try…so I don't know if it would work.

Layer volumes in planar cross sections with varying thicknesses.

Add to that the capacity to vary density with distance/position through volume wrangle.

Also, defining color/diffuse values.

Wouldn't work with the need to have ‘fly’ through at any viewing angle/position.

But perhaps could work with some limited ability to change viewer position from a landscape perspective.

That seems like a lot of work for something that Octane can literally do with a click of a button. As I said, when you get used to what GPU renderers can do with atmospherics, it's really difficult to go back to doing it any other way.

lookdev
In Clarisse, it’s done with. Volume box

Same in Houdini

tamte

lookdev
In Clarisse, it’s done with. Volume box

Same in Houdini

That's just a fog though. An atmosphere has chromatic affects base on physical properties such as Mie and Raleigh scattering. I've never seen a renderer, other than some game engines actually implement a real atmosphere.

I looked at Octane, and it just has a simplistic volume atmosphere. Okay for fog, but not really for distant mountains or visualizing a planet from space.

Maybe that's all OP was looking for, and then it's a fairly basic feature of which Mantra is capable.

jsmack
Maybe that's all OP was looking for, and then it's a fairly basic feature of which Mantra is capable.

that's what it sounded like from original description
obviously Rayleigh scatter would be nice, but one step at a time

Curious, is there a simple way to get shots of the earth from outside the atmosphere in Mantra or any of the plugin renderers like octane or redshift? I want to quickly get a shot of the earth with realistic atmosphere using real units and sun positions.

I used to work in astro visualization (example project/image here https://www.tii.se/projects/ice) and this effect can be achieved in realtime in OpenGL/GLSL since many many years but I hope I don't have to write my own shaders this time.

I tested faking it all using a regular smoke volume around a sphere using Redshift demo. No view and light dependent scattering as far as I can tell but for most uses it might be ok:

filipw
Curious, is there a simple way to get shots of the earth from outside the atmosphere in Mantra or any of the plugin renderers like octane or redshift? I want to quickly get a shot of the earth with realistic atmosphere using real units and sun positions.

FWIW…there's this:

https://www.videocopilot.net/blog/2018/09/new-tutorial-orb-plug-in-now-available/ [www.videocopilot.net]

If you're looking for easy, it's hard to get easier than this, and it's free. Having said that, it only works in AE which can be a tough one to swallow for many people.

Hehe, quite surprising that AE should be the answer. Sadly, for my case I need to render to fisheye (it for a dome show)in 4kx4k in the end so maybe it cannot handle that.

I found Matt Ebbs 2012 article and example of Mie scattering http://mattebb.com/weblog/rendering-clouds-with-the-mie-phase-function/ [mattebb.com]
That might be a starting point. I am just surprised this is not a built in shader in todays offline renderers. I mean in the realtime world the GPU gems 2 article from 2004: https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter16.html [developer.nvidia.com] is used all the time.

I do believe Octane has a planetary atmosphere shader. I mentioned it to the Redshift developers but they didn't seem particularly keep on spending time on it.

Tried out the Octane 4 “Planetary environment” and it indeed is a nice planet with atmospheric effects. The only problem is that it cannto be animated as far as I can tell. You just set an altitude that represents an offset from the surface of the planet. Maybe there is a way around it but I did not find one in my brief testing.
Also tried some hacky thing using Matra that looked promising but was way to slow. Hmmm hmmm hmm

If someone who knows more about shader writing than me wants to try this, I stumbled across this recent (2020) paper from someone at Epic Games. It could be a good start.

https://sebh.github.io/publications/egsr2020.pdf [sebh.github.io]

Here is the very easy tutorial for creating volumetric fog using Mantra - https://youtu.be/ZlVPY6lpAs8 [youtu.be]

There are some volumetrics in Houdini; there's a Sky SOP, a Cloud SOP, and a Cloud Noise SOP. I also followed a tutorial using a Volume VOP.

In Karma though it's still pretty baffling. And the Sky and Cloud SOPs are very slow, probably partly because they keep blowing up Optix, so I'm not getting any GPU acceleration even though I have a 3080 with 16GB. But I think Karma XPU is still in beta?