How to Render Phoenix FD VDB liquid caches with Arnold in Maya?

[sean_brown]

In this Chaos tutorial they show its possible to render Phoenix VDB cache with Arnold in Maya with an explosion. I tired it with the default Tab Water Sim but it didn't work. Just got a volumetric full of fog. What would be different in setup when doing this with water?

[georgi.zhekov]

Hey,

If you're simming the cache with Phoenix in Maya - for liquids such as the tap water you can render them without going through the vdb format. You just need to go to the Rendering rollout of the Phoenix simulator > Mesh > Mesh type and set this to Maya mesh.
This will make the liquid render as a regular Maya mesh and you can render it directly with Arnold. You can find more about the mesh types here - https://docs.chaos.com/display/PHX4MAYA/Mesh

If you have an already simulated VDB file coming from Phoenix you will need to select the Temperature_phx channel in the Arnold Volume node, set the type to Implicit (by default it's Volume) and use the Temperature_phx as a Field Channel.
Then you can set the threshold to 0.5 and you should be able to render the mesh.

Cheers!

[sean_brown]

Hey,

If you're simming the cache with Phoenix in Maya - for liquids such as the tap water you can render them without going through the vdb format. You just need to go to the Rendering rollout of the Phoenix simulator > Mesh > Mesh type and set this to Maya mesh.
This will make the liquid render as a regular Maya mesh and you can render it directly with Arnold. You can find more about the mesh types here - https://docs.chaos.com/display/PHX4MAYA/Mesh

If you have an already simulated VDB file coming from Phoenix you will need to select the Temperature_phx channel in the Arnold Volume node, set the type to Implicit (by default it's Volume) and use the Temperature_phx as a Field Channel.
Then you can set the threshold to 0.5 and you should be able to render the mesh.

Cheers!

Hi georgi.zhekov , Thanks for this info. I tried your suggestion but when i change it from Volume to Implicit the sim doesnt render in Arnold. it just disappears. When i render as Volume all i see is smoke but no fire/heat. See my screenshots to see if I am missing something. I appreciate your help.

EDIT: I figured out why the heat was missing, i forgot to enter Temperature_phx into the aiVolumeSampleFloat. But I am still wondering why your suggestion of changing it from Volume to Explicit is not working for me and how it may improve my render.

Also, what would I do differently to make a fire sim, like a candle, work in Arnold? So far I cant get the default candle sim to work with the current setting/workflow. It just disappears .

Maya Viewport


Arnold render as volume



Arnold render as Implicit, Field Channel set to Temperature_phx and threshold set to .5



aiVolume node material editor settings

[Svetlin.Nikolov]

Note that the fundamental difference between the explosion and the tapwater is that the explosion renders as a volume, while the tapwater and any liquid simulation just renders as a regular mesh.

In general, if you want to render liquids with other renderers, you could go to the Rendering rollout -> Mesh sub-rollout, and switch the Mesh Type to Maya Mesh (https://docs.chaos.com/display/PHX4MAYA/Mesh) - this way the Phoenix Simulator would render directly in Arnold - you just need to apply a surface material to it.

Cheers!

[sean_brown]

Svetlin.Nikolov georgi.zhekov , how can i render basic a fire sim with Arnold. I followed the same steps for smoke and just replaced smoke_phx with Tempurature_phx and got close but it still isnt quite right. Are there any other steps that are different in the Chaos video tutorial on rending the explosion sim but just fire instead? Arnold is still lacking the detail in the fire.

see my comparison below

rendered in vray


rendered in Arnold

[georgi.zhekov]

It's all about playing with the settings in the Arnold shader. You can adjust the Blackbody intensity and the Blackbody contrast values in order to produce a similar result.

[sean_brown]

It's all about playing with the settings in the Arnold shader. You can adjust the Blackbody intensity and the Blackbody contrast values in order to produce a similar result.

I did adjust those settings they look nothing alike.

[georgi.zhekov]

Since Arnold and V-Ray have a bit different controls and ways of doing things, not sure you can get the exact same result, but here is my take on it without being an Arnold expert.

Attaching the results I got and the settings I used. It's not in the screenshot, but the density in the aiStandardVolume shader is set to 0 so that only the temperature is shaded.

[sean_brown]

Since Arnold and V-Ray have a bit different controls and ways of doing things, not sure you can get the exact same result, but here is my take on it without being an Arnold expert.

Attaching the results I got and the settings I used. It's not in the screenshot, but the density in the aiStandardVolume shader is set to 0 so that only the temperature is shaded.

Hi, can you share you scene file? When I tried your settings its didnt look the same at all.



Also whats your Phoenix output settings? maybe i dont have the right grids checked off? Here were mine.

[georgi.zhekov]

Here it is. The output settings look good, maybe it's something else.

The Phoenix nodes are hidden, you can unhide them, run the sim, then load the caches in the aiVolume node and it should work.