Volume Shader --Godrays through volume (REVISED and UPDATED)

[Justin K]

Hey all, posted this a bit ago but I am updating the post with a lot more context.  

 

I am trying to find a way to render volumetrics in houdini.    More specifcially, I have a night scene, with street lights.  Because it will be raining there will be volumetric influences on the light sources.  I want the light sources to be cut with god ray like light patterns, or at the very least have convincing fog throughout the scene.  I am struggling to achieve this affect with mantra.  

The first two images are what I am using as reference.  The first is the scene I am trying to emulate in 3d --complete with a rain sim and an umbrella rig (ya the same one from a previous post  ---all help was apprecaited)

(source: https://angelganev.deviantart.com/art/City-Nights-III-Day-82-700866138  )  pic 1

 

The second is an inspiring render I cam across with very well designed volumetrics in the sky--and convincing wet maps on the ground level

(source: https://www.behance.net/gallery/35226551/52Hz )   pic 2

 

The focus now is on the volumetrics.  

 

 

I have now attached the master scene file with the assets included as a zip in hopes of getting some detailed help--its a pretty simple file.    

 

Now, Ive been trying to use this as a reference 

  https://www.sidefx.com/tutorials/god-rays-light-beams-through-volumes-updated-20170508/

but am struggling with the implementation.  Something in materials seems to have changed in houdini 16 (or I am more likely just missing something).    

Overall, the suggested technique seems to be to simply apply a volumetric shader to a bounding object and use that to apply volumetrics to the scene.  This approach seems to work as intended but only if the camera is not within the bounding volume which in this case defeats the purpose.   See pics 3 and 4--one pic shows the volumetric box from an external view-- and shows its affect on the light sources--the second is inside the volume, where nothing seems to be happening--even if I try to trick it an dreverse the normals the result is just wrong.  

 

 

Is there a way to do this on the shader level?   

I know I can use an isooffset and build volumetrics on the object level, but when I was working with isooffsets my render times were ridiculous.  I dont want to have a scene with crushingly long renders if I don't have to.   It was pointed out that if you keep your volumetric sample 'cranking' on the material rather than scene level your results will be much faster--hence the reason Id like to implement the shader level approach if possible.      

 

Again, any help would be appreciated, Thank you!

 

 

 

 

 

 

 

 

 

 

Painting_JK_01.zip

 

Edited May 4, 2018 by JKeil

[adrianr]

Uniform volume is still in 16.5. Check in the Material Palette. 

[Justin K]

14 minutes ago, adrianr said:

Uniform volume is still in 16.5. Check in the Material Palette. 

thanks adrianr-- I am currently using 16.0--16.5 is not working on MAC OS for me :(--at home I have 16.5 but not at work.  

[adrianr]

There in 16 too  Same place.

[Justin K]

16 minutes ago, adrianr said:

There in 16 too  Same place.

Joey struggles here.. Is it supposed to be located here?  

[adrianr]

The panel will be in a different place depending on which desktop you're in. But you can always add it to any pane. 

[Justin K]

3 minutes ago, adrianr said:

The panel will be in a different place depending on which desktop you're in. But you can always add it to any pane. 

 

Thanks Adrian-- implementing and working with it now.  

[AlSk]

I'm wondering what's the current workflow for fast volumetric atmosphere lighting in H18?

So far I've tried different techniques, but none was really convincing:

• Atmosphere OBJ is officially depricated since 17.5
• VDBs are chunky in close proximity.
• Uniform Volume had grainy noise near the light despite high samples (16x16) and doesn't work with Micropolygon Rendering. Also it triggers some error concerning displacement with default settings on a default Box OBJ. So it seems also sort of outdated to me.

Edit:

I also sent this question to SideFX Support. That's the answer I got:

Quote

Uniform volume or voxel volume are still current workflow. Instead of increasing camera samples to reduce the noise, I'd suggest increasing the "volume samples" (in uniform volume shader) and "stochastic samples" (in mantra ROP).

 

Edited March 16, 2020 by AlSk