Hide Underwater Liquid Mesh

[Joelaff]

I have a scene where an object drops into a "tank" of water. My camera is underwater looking up. The simulation is done and good.

I am seeing some of the liquid around the object that drops in the water (which was a collision). This doesn't look so good, and I would like to remove that.

However, if I sue a clipper then due to the IOR of the water I see the clipper's refraction.

I can get rid of most of the objectionable part by using a volume to exclude displacement from the liquid surface around my dropped object. However, I'd really like to find a way to just hide all the liquid that is surrounding the dropped object.

Any way to do that? Thanks.

I am not using Underwater Goggles because this caused problems early on, and everything it setup without it. I instead use IOR < 1.0 for my air bubbles.

[Joelaff]

I found a partial solution that is sooo close!

So if I use Mesh mode for my fluid simulator instead of OceanMesh then I can apply modifiers to it (specifically Volume Select with a Mesh Object as the volume and Delete Mesh to delete the selected polys). This works in Mesh mode, but sadly I need Ocean Mesh mode.

So I am probably going to have to render a cleanup pass of the area in question in Mesh mode and combine them in post. Extra sad since this render is horribly slow.

Open to any other thoughts. Thanks.

[Svetlin.Nikolov]

Hmmm, how about a simulation-time solution - place a non-solid, non-renderable box underneath the ocean level and plug it into a source in volume brush mode with 100% brush effect?

[Joelaff]

Thanks for the idea, but at t this point I have had about enough simulation of this scene

Was hoping for a render time solution. The two pass (with a region-- don't think GPU does render masks yet) will probably have to work.

[Joelaff]

It would be really cool if the Ocean Mesh mode could also support modifiers. Even with changing topology modifiers like volume select are quite useful.

Thanks.

[Svetlin.Nikolov]

Hmmm, doesn't it support modifiers right now? Can you describe your setup?

[Joelaff]

I can't test it right now because I have all hand on deck rendering something, but what I was seeing was that with Ocean Mesh mode the liquid would not render (hotfix 1 GPU) when I had modifiers applied. The liquid mesh simply did not show up at all in the render.

The modifiers I had were Volume Select (WSM) (using a mesh object as the selector in Face mode), and Delete Mesh (WSM) to delete the polygons inside the volume. When I switched the Liquid to Mesh mode it worked fine.

[Svetlin.Nikolov]

Huh, that's right! Reproduced it here as well - On V-Ray CPU all 3 modes render after vol select + delete mesh, but on V-Ray GPU only mesh and cap mesh render.

Will look into that, thanks for reporting! Otherwise, all modifiers are supposed to work on all the mesh modes - in theory the Phoenix mesh should be just like any other mesh you have in the viewport. When there are cases like this one though, they are likely to be bugs...

[Svetlin.Nikolov]

Alright, so neither does a simple Noise modifier show up on V-Ray GPU when rendering in Ocean Mesh mode...

[Joelaff]

Cool. I am glad it is a bug, because that means it is probably easy to fix (in this case-- not that bug means easy to fix, as a developer since 4 years old I get this!) But I bet this one is something simple given the criteria.

Really I am glad it is something that is supposed to work.

Thanks.

[Svetlin.Nikolov]

Oh yes, should be an easy one. Especially since Cap Mesh with mods DOES render, should be something stupid somewhere...

[Svetlin.Nikolov]

Yay, found it - the fix will be in tomorrow's Phoenix nightlies (no need for a newer V-Ray for this change).

Thanks again!

[Joelaff]

Thank you!

[Svetlin.Nikolov]

Hey, just a heads up: one more fix went in today and will be in tomorrow's nigtlies: the ocean mesh was not cleared if it was already shown in the viewport preview when starting a V-Ray GPU rendering, so it had low mesh detail. When rendering a sequence this affected just the first frame. Or if the ocean was not shown in the mesh preview, there was no issue at all.

[Joelaff]

Interesting. That may be something I was seeing here. Would this apply to frames rendered one at a time with 3dsmaxcmd.exe ? Or does that GUI could never get called in that case?