Water issue: difference between viewport and render

boubakeurjohn

Hello,

I'm running into an issue when working with the Cave Island product: in the viewport, water looks very nice (left), but when rendering (right) it lacks a lot of details.

I didn't change much in the render settings. I tried turning up renderding quality to 3, max samples allowed to 10000, max rendering time is set to 7200s (though it gets rendererd before that limit is reached), but it didn't change anything...

Any idea on what I need to change to get the same quality I have in the viewport?

I don't have the same kind of issue with other products.

Thanks for your help.

 

JonnyRay

It looks like the link to your image is broken (or my company firewall is blocking "non work related" links again).

One thing I will say in general is that the Iray preview does not support certain Iray features. Noticeably this includes certain volume effects. This could be why there is a difference. One thing that would be quick to try to see if this has any effect is to make sure the water surface settings are set to "Thin Walled: ON".

boubakeurjohn

Thin Walled was set to OFF, I changed it to ON and Viewport and Render are now consistent and have great details.

New issue is that I liked the refraction I had in the Viewport with Thin Walled to OFF... I'll try and play with the Refraction Index/Weight settings.

Thank you JonnyRay.

Padone

The water in the viewport is totally missing reflections so I don't get why you consider it better. it is not. Due to the fresnel effect you will get a more "transparent" water by either making the water less deep and/or taking the shot more from the top. Changing the ior may also work but it is not realistic.

JonnyRay

boubakeurjohn said:

Thin Walled was set to OFF, I changed it to ON and Viewport and Render are now consistent and have great details.

New issue is that I liked the refraction I had in the Viewport with Thin Walled to OFF... I'll try and play with the Refraction Index/Weight settings.

Thank you JonnyRay.

With Thin Walled turned OFF, Iray treats treats everything behind the plane (from the camers's point of view) as if it were in the volume of the material. So refraction, etc. works because it thinks the light has bounced off your objects and passed through the water/air boundary.

With it ON, it treats a single sided pane as if it were the entire "volume" of water, but with infinitesimal thinkness. So, technically it thinks you have a thin film of water, but anything you think is "in" the water, Iray thinks is actually in the air on the other side of the film. This will cause issues with refraction since there isn't enough "depth" to the water to make light bend very much.

Another option would be to replace the plane that represents the water with a cube of the same size, but deep enough to encompass the parts of the scene that should be under the water. You have to be careful with this though as the sides of the cube could look a little funky if they are within the image. Better to oversize the cube so that the edges are outside the frame or are masked by other objects in the foreground.