I’m working on a large scale underwater scene - or actually it’s partially underwater. When rendering, everything is way too dark probably due to distance. I couldn’t fine the parameters that helps extension of underwater visibility. On rendering only visible thing is partial VRayPlane. The teapot is located at the point of interest.
The other thing; is it possible to cancel the IOR 1.33 effect? I don’t want to distort the camera in order to match the underwater rendering to surface rendering.
Hey,
When rendering underwater the things that will influence your renders are:
- the lighting - how strong your lights are
- the liquid shader - if you have the Underwater Goggles option turned on a surface gets automatically added in front of the camera, using the same material that is assigned to the Simulator, and this way mimics the effect of real life underwater goggles. This way the ocean volume receives the Fog color from the material assigned to the Simulator, and the field of view shrinks when the index of refraction of the material is above 1. So if your fog color of the V-Ray Material is too dark or has a high multiplier the render can become too dark
You can find how the Underwater goggles option affects the rendering here - https://docs.chaosgroup.com/display/…erwaterGoggles
So try disabling the Underwater goggles and it should look brighter and without the refraction of the liquid material.
Yes, this happens because the ocean surface is generated only in the camera view, which can lead to problems when using camera motion blur, using reflections, using refractions with Underwater Goggles enabled, or when the ocean casts shadows on objects underwater.
For such cases you need to use the Off-screen margin option in the Rendering rollout of the simulator. It allows you to extend the ocean further from the borders of the camera view in order to solve such issues. The value is a percentage of the image size. So start increasing it gradually as if you enter a large value it will consume a lot of memory.
Then keep the Underwater goggles on and lower the IOR of the liquid material.
Cheers!
The black rendering of the far underwater objects is related to the fog color of the material. There is a multiplier of this value, otherwise would be impossible to adjust the color in cases of almost purely transparent materials (like the water)
As Ivaylo said, adjusting the Fog multiplier for the water material should do the job.
Ah I got what you mean. The places where there is no geometry behind, will render black indeed. This is due to the way the fog color of the V-Ray material works.
The easiest solution would be to place a large box far back to act as a background.
The real water is not totaly black because it has small diffuse component, i.e. it acts like thin smoke. To achieve the same effect you have to add some dummy volumetric object with constant opacity, but keep in mind that this may increase the render times. On the other hand you can get the “god rays” effect as a bonus, if you need it
Thanks again,
I created a trumpet look alike cylinder surrounding my underwater scene. It was much better, but I’m not even close to what I’m looking for. I think the effect can’t be achieved with underwater goggles. I will try next V-Ray fog. Do I need an atmospheric helper if I want to add some variation depending on the depth?
I think without variation will be fine.
Hey, @JuhaHo , indeed when there is no geometry behind the ocean fog, V-Ray understands that the fog color should continue building up infinitely, so it becomes this dark.
If you want to have varying density, the environment fog would indeed be a better choice - the vraymtl’s fog can’t be mapped with different densities in depth.
Still, how does it look with your own cylinder geometry?
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.
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?
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.
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.
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.
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.
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.
