Bizarre Cycles rendering issues with large planes

Hoping someone here might be able to help me with an issue I’ve been having.

I’ve been trying in vain for some time to make a large scale ocean. I’ve tried several different things, but I always end up having trouble with the horizon plane. For whatever reason, it will often ‘change’ colour, per frame.

I have it set up in the following way:

  • A tiled Oceansim setup for high res water (close to the camera).
  • a single oceansim (with large spatial size) for medium res water, faded out with a spherical gradient.
  • a large circular plane, stretching to the ‘horizon’ (approx 3000m) which uses a glossy shader mixed with a texture to provide simple ‘foam waves’.
  • The scene is lit by an HDR, as well as a sun.

I’ve done several variants of the plane, but I always get the alternating colour per frame.

I’m wondering if this is a bug with cycles for large planes, and if anyone knows a way around it.

I’m using Blender 2.77a, rendering on CPU.

Here’s an image that shows the issue on alternating frames and my scene setup. I’ve also included the material node for the large plane that’s causing the issue.

If you look at the image in the top right you can see the issue with the far plane - on some frames it’s very dark, others it is correct. It’s never consistently the same dark either - if I play it back it will vary back and forth.


It might be some kind of depth fighting or precision related problem, although Cycles should be way more immune to that than opengl view. If you move the far plane down a bit more, to increase separation between two objects, does it change anything?

Another thing to try is to render the far plane alone, without the mid and close waves. Does it still flicker?

Is is really “every other frame” 1 good, 2 bad, 3 good…?

What happens if you change that shader to a single glass node?

Worth a try, increase your bounces

I may be having the same issue: every now and then the character’s eyes or clothing will suddenly flash, to what I believe is one of the diffuse/glossy nodes as if it had no texture controlling the factor in the colors. But it’s not every other frame, it’s random. Maybe every 20 or so. The one thing I notice is the materials that are having the issues are quite complex, with multiple shader types used.



Fascinating, I did both of these.

The first test appears to have fixed the issue - although the plane was 5 metres under, it must have still been intersecting with part of the oceansim geometry (potentially the medium res one in the distance) causing the effect.

The second test, rendering the plane alone seemed to fix the issue, but I found the plane inexplicably changed colour on a few random random frames (but only half of it, as if the UV map was triangulated). I assumed that this perhaps This must be due to it intersecting with a ship object, which I left rendering. Putting this variant of the plane to -10 metres appears to have fixed the issue also.

I should be able to get away with having the plane so low. It certainly saves alot of headache. Now only if I could figure a way to get my high res and my medium res water colour to blend better…

Really appreciate the help everyone!

Interesting - I thought perhaps mine was an issue with the complicated geometry generated by the ocean sim modifier, or some weird math problem with the giant scale of my ocean plane - but this could be potentially be something else?

I’ve had something similar happen once when I was rendering an animation using linked materials or textures on a network server - I assumed that during a couple of frames the network hiccupped or went down, and it rendered it sans the node setup. But it looks like all your other node setups are rendering fine.