Max VRayVelocity Element

[djanim8]

I did a dust simulation with Phoenix, selected the Speed and Velocity output grid channels, and assumed it would be included in the VRayVeolcity render element so I could use it for blur in post. I didn't get the velocity included in the render element. Is there something else I need to do? Or is Phoenix just not able to be included in a velocity element?

[Svetlin.Nikolov]

Hey,

Did you render in Volumetric Geometry mode?

Cheers!

[djanim8]

It was on Volumetric, I'll render it again and see if it works.

[Svetlin.Nikolov]

Yup, please check Geometry mode - this is where render elements would show up.

[djanim8]

I've never worked with the Volumetric Geometry with the fire sim before, so I can't figure out what's going on. Where the "dust' is, it's rendering out as pure white now. What needs to change to go from Volumetric to Volumetric Geom?

[Svetlin.Nikolov]

Hummm, are you in Max or Maya and which Phoenix version are you using? The only thing that changes is that the Approximate scattering of Phoenix gets disabled, so you might get a darker image. However, there is one more thing to watch out for if you haven't already gotten a warning message - you need to raise the Max Transparency Levels of V-Ray in order not to get the back parts of the volumes cut out.

[djanim8]

I'm using Max 2018 with Pheonix 3, the phoenixFD_adv_30403_max2018_vray_30_x64_27826 nightly. I'm attempting to render out more so I can get a better view of it, but it takes a while on my current machine.

[Svetlin.Nikolov]

Oh, definitely grab a latest nightly first. Volumetric Geometry will render more slowly than Volumetric though - you could use it just to get the render elements, but render everything else in Volumetric. Also - make sure to have the Phoenix Velocity channel enabled...

Cheers!

[djanim8]

I'm not able to render it with the Vol Geom. It keeps crashing max trying to do it that way.

[Svetlin.Nikolov]

Hey, you mean with a latest nightly? In this case, definitely send the scene over to Support and we have to fix this ASAP.

[djanim8]

Oh no, it was crashing before. I just can't get it to fully render out with the vol geom.

Using the resume render option, I managed to get it to render. This is what it gave me with the vol geom option. Seems like the "density" of the white ares actually change every time I render it too.

[Svetlin.Nikolov]

Hummm, this looks exactly like it would if you have too low Max Transparency Levels in V-Ray. How many do you use right now?

[djanim8]

I've never messed with that setting, so it's at the default of 50. Attached is the render (without blur) with just volumetric (not geom).

I've also attached the VRayVeolcity output and the post-blurred image using ReelSmart Motion Blur. This is the first time using both VRayVelocity and RSMB Velocity.
The scene is setup with the car moving straight down the dirt road, with the tires rotating. The camera is linked to the car. With a VRay render, the blur would show the background, foreground, dust and tires blurring. I've tried to render the scene this way, but even on a 16 core, 192 Gb of RAM machine, it crashes when rendering blur, so I'm trying to use the VRayVeolcity to add the blur. The car shouldn't blur since the camera and the car are moving at the same velocity. I assumed this would be how the VRayVelocity would work as well. Does it not work like this?

[Svetlin.Nikolov]

You gotta increase the max transp levels to something like 1000-2000 and the white artifacts will be resolved (you should have gotten a message box about that). We gotta check if the velocity render element is correct with a moving camera and moving Phoenix grid...

However, if you are getting a crash, it would be best to send the scene to Support so it can be fixed, and not just worked around

Cheers!

[djanim8]

I think I did get a warning, clicked OK without reading real quick and tried to get it back. It was probably that. I'll send the files to support and see if they can help. Do you all have Forest Pack there? The environment was done with that in the scene.