Render Wet Map To File

[tommygdawg]

Hey, all

I'm doing a water simulation over live action footage. I'd like to be able to render my black and white wet map to it's own image sequence or render element without the original simulation on top. This would allow me to use it as a luma matte in compositing to color correct my source footage to be darker where the simulated liquid has splashed, thus making the ground in the footage appear wet. However, when I hide the Phoenix Liquid simulator, the wet map no longer functions. Any tips on how to do this?

Thank you!

[Svetlin.Nikolov]

Ah, wetmap disappearing when the simulator gets hidden sounds wrong. Can you describe your setup in more detail? Do you mesh the wetmap particles, or use them as a mask for a blend material of dry and wet materials?

[tommygdawg]

Setup is pretty straight forward. Got a simulator spewing liquid onto a plane generating wetmap particles. Using a standard 3DS Max camera (not a physical camera). Here's a couple screengrabs:

Render with phoenix simulator:

Clearly, it's working above. The area under the liquid and where the liquid has been consumed is rendering as white (or rather blue due to the dome light, but that's fine), which is what I want. But as soon as I hide the phoenix simulator, it just all renders completely black.

I'm currently using 3DS Max 2020, Phoenix FD 4.41.00 and V-Ray 5 Update 2.1 CPU.

[slavina.nikolova]

Hey,

The Wetmap seems to work properly, even with a hidden Simulator in my test scenes. Can you send us a simplified scene to see what is causing the problem?


Thanks!

[tommygdawg]

Attached here! You should just have to run the simulator for a few frames to get enough liquid on the floor to generate a wet map. Appreciate you taking the time to look into it!

[slavina.nikolova]

Hey, thanks for the scene!

I can see you are using Distributed Rendering.
Can you try to render the scene locally on your machine and see if the Wetmap is rendered correctly, because it seems to be working on my machine?
Another important thing to check is whether the network machine has access to the caches you are using. Here is a page with more info about the Distributed Rendering - https://docs.chaos.com/display/PHX4M...uted+Rendering



Cheers!

[tommygdawg]

Tried disabling network rendering and I also have just updated to 52002. The wet map still disappears when I hide the phoenix simulator. I have also tried leaving it unhidden and going into the object properties and unticking "Renderable", which also makes the wet map disappear. This is very strange. Are you using 3DS Max 2020 with V-Ray 52002 and Phoenix FD 4.41?

[slavina.nikolova]

Hey,

We were able to reproduce it, but here it seems to happen at random. We are looking at it and will ping you as soon as we have more information.


Thanks!

[tommygdawg]

Fascinating. Thank you for looking into it!

[slavina.nikolova]

Hey,

The problem seems to be related to V-Ray Motion Blur. As a temporary workaround, you can try disabling the Motion Blur and see if the result works for you while we dig deeper into the problem.

In addition, we suspect that the Wetmap is not visible in the first render when loading a scene with a hidden Simulator. If you press render again, it should appear - we are also checking this problem.


Hope this helps!

[tommygdawg]

Thanks for getting back! Disabling motion blur did fix the issue. However, no amount of hiding, rendering, unhiding, rendering, etc. was able to get it to render properly.

I also just performed a test. The standard 3DS Max camera was created from the Syntheyes 3D track. So, I've just made a physical camera, aligned it to the standard camera, set the FOV to be the same, and then linked it to the standard camera. This essentially completely replicates the standard camera. I then activated motion blur on the physical camera itself (in the Modify tab) rather than in the V-Ray render settings tab. This allows the wet map to render with motion blur whilst hiding the simulator.

So, it seems that the issue is specifically with using the motion blur from the render settings area of V-Ray, rather than directly on the physical camera itself.

Thank you for helping me track this down!

[Svetlin.Nikolov]

Ohh, this is very good info, thank you!

[slavina.nikolova]

Hey,

The problems should be fixed in the latest Phoenix 4.41 Nightlies - https://nightlies.chaos.com/main#/ph...ghtly/20220208.
In this topic you can find useful information about how to get Nightly Builds: https://forums.chaosgroup.com/forum/...nightly-builds

Please ping us in case there are any issues.


Cheers!