Large scale underwater scene renders almost black

[JuhaHo]

Thanks Svetlin,

With the cylinder I got the background somewhat I want to have, but not with underwater effect. I'm now working on V-Ray environment fog to make the illusion, there's water between the camera and underwater objects and also which objects are far away. When that's the case, I need volumetric effect which the goggles didn't provide.

Is there any good V-Ray environment fog tutorials? I'm not getting very good results: No fog at all or all foggy - nothing between.I'm now eliminating reasons for that in a separate scene with a teapot, camera, light and atmospheric apparatus only. Rendering is annoyingly slow. It takes about an hour to render a teapot in the fog.

[Svetlin.Nikolov]

Ouch, maybe alternatively try adding a new Phoenix Simulator and without simulating, just change the Smoke Opacity to come from a Texture? It won't be infinite like the env fog though...

[JuhaHo]

Ouch, maybe alternatively try adding a new Phoenix Simulator and without simulating, just change the Smoke Opacity to come from a Texture? It won't be infinite like the env fog though...

And that should be a clouds sim template?

[Svetlin.Nikolov]

It could be yes Or do you mean the Clouds toolbar preset? That one is too complicated for this use case and it requires simulation too.

[JuhaHo]

Here's my test scene rendering. Obviously it requires some tuning. I have two Phoenix simulators: one for the ocean surface and one for underwater fog. The opacity map is cellular and I will return to that later.

[Svetlin.Nikolov]

Sweet! Looks like you may need to increase the off-screen margin option of the ocean though. In the upper right corner there is a difference in shading that often happens because the ocean mesh is built only in the camera view, so the shadows its border casts sometimes become visible in the render.

[JuhaHo]

Here's another,

I still need to figure out how to make the fog invisible above the surface as it can be seen behind the teapot. I don't see the caustics neither. The light should travel through the water surface.

[JuhaHo]

I googled for underwater photos and this seems to be good starting point:

[Svetlin.Nikolov]

As for visibility above the ocean mesh surface, wouldn't using Cutter Geometry solve it? https://docs.chaosgroup.com/display/...ing-Parameters

[JuhaHo]

As for visibility above the ocean mesh surface, wouldn't using Cutter Geometry solve it? https://docs.chaosgroup.com/display/...ing-Parameters

Thanks,

I'm using camera clipping plane to cut the water surface. I noticed, I need to define water material Fog multiplier above 0.1.

[JuhaHo]

Beginning to get some progress. Still a long way to go. This is one pass rendering from V-Ray VFB

[Ivaylo Katev]

Just to mention that the underwater lighting setup is very important here. In general, there are three options - to enable "affect shadows" of the water material (is this your approach?), this is the fastest possible solution with the worse result, it allows to see the underwater shadows and the fog, but is lacking the caustics of the waves. Just for information, the lighting mechanism is using straight rays to calculate the direct lighting called "shadow rays", the "affect shadows" option allows them to penetrate the refractive materials as if they are "transparent" (opposite to the common sense, both the words have different meaning).
The other two possibilities are to enable the caustics, or to use brute force GI+ HDR environment texture that has large bright spot where the sun must be. The caustic approach should be the best one, if there are no complications. It uses cached light that is precalculated and in the most cases is pretty good. The third solution is an alternative that can be used if the caustics are not suitable for some reason. It works in kind of opposite to the caustics way - the underwater objects are spawning indirect GI rays, that are refracted by the surface and hit the bright spot of the environment (thats why it must be large enough, to provide good chance to be hit). One possible reason to use this solution instead caustics is for example the presence of brushed metallic objects under the water. The caustics and other light cache techniques are relying on the diffuse component of the BRDF, but the metallic setup does not have one.

[JuhaHo]

Thanks Ivaylo,

I think I tried all the suggested settings, but no luck so far. Other ways I'm getting some progress. I'm not sure if the underwater color is the final one, but don't know any better either.

Attached is my caustics settings. Since this is only a teapot scene I think I can share it if there's need to.

[Joelaff]

This is getting to a pretty cool look. Would love to see the scene if you are able.

We did some similar stuff recently that was cameras underwater. I faked the caustics and the volumetric shadows in post. The render times were already quite high due to 100 million + bubbles and DOF.

[JuhaHo]

Thanks Joelaff

Heres's my test scene. This is for one pass rendering. After that I have changed the fog color to more greenish. I'm struggling with the caustics. I just don't see it.