Black specks on water surface

[sboerner]

I'm getting artifacts when I render a water shader applied to a lake object. Nothing fancy here, the object and shader are all left at default settings, except for a small increase in the roughness value of the water shader. Light source is at a fairly low angle, elevation 9, and the surface is backlit.

Renderer micropoly detail is 1.0; AA is 6; filter is Narrow Cubic.

Running another test render with filter set to Cubic B-Spline. Not sure what else to try.

[Oshyan]

Strange indeed. Can you share the TGD file?

- Oshyan

[sboerner]

Thanks, Oshyan. File attached. Changing the filter made no difference. Increasing the smallest scale in the water shader reduces the problem but doesn't eliminate it. (Of course that also reduces the amount of surface detail.)

Appreciate your help.

[Oshyan]

OK, so this is another case (interestingly) where increasing the Ray Detail Multiplier fixes - or at least improves - the issue. In this case I would guess it's because of the increase in roughness causing more inter-reflection. It should not cause such a dramatic change with such a small Roughness adjustment, in my opinion, but that seems to be what's going on. So, you can find the Ray Detail Multiplier with the instructions in this thread:
http://www.planetside.co.uk/forums/index.php/topic,22280.0.html
You're looking for the Ray Detail Multiplier in the Subdiv Settings internal node.

This setting will be shown on the Render node settings in the future. Note that it also increases render time.

- Oshyan

[Dune]

For this kind of water you may not need a water shader at all (no transparency of it), and could do with a reflective shader and some vague greenblue 'water colors'.  Speeeeeds up render time, and can even be used to soften reflections (if needed, as it will increase render time again).

[sboerner]

Thanks, Oshyan. Bumped that value up to 0.5 and am running a test now. For the record, the subdiv settings node was hidden beneath one of the other nodes when I opened up that level.

I may end up taking Dune's advice to speed up the render – this needs to be finished today to meet a deadline.

Thanks to all.