Depth of field causing patterns on skin?

warrenao

Please note this is not the same quesiton as the one regarding subsurface shaders and moiré patterns in skin. This question is about an apparent interaction between depth of field and patterns in skin.

DS 4.9.3.166, MacOS (10.12.4), 3Delight engine.

Models (human, G3). The skin is not the Iray material. No additional shaders are being used on the skin surfaces, just the generic out-of-the-box materials.

Lighting is generally distant light, with raytraced shadows, different intensities of lighting, different levels of softness on shadows.

What is happening:

When I set up a camera to use depth of field, sometimes the render produces odd ring-like or slice-like patterns in the models' skin. When I turn off depth of field, this effect vanishes.

The first image shows a model whose skin is behaving correctly. This image was rendered in 3DL using a camera with DoF on, and distant lights for the lighting sources: A rim light from above and behind, at 150% intensity, raytraced shadows at 10% softness; a key light (distant eye-level, right of camera) at 80% intensity, raytraced shadows at 30% softness; and a distant fill light (eye-level, left of camera), 40% intensity, raytraced shadows at 70% softness. Shadow intensity on all three lights is 100%. The camera's f/stop is around 15. The lights are generic 'white' sources (rgb 255, 255, 255).

The second image shows another render with the model moved and the pose changed. The camera's f/stop is around 30 here. Apart from that, nothing has changed at all.

Subsurface shading is on in both renders. Changing the SS group does not have any visible effect.

What in the world is causing that weird pattern? It looks almost as though the model's geometry is somehow leaking through the render engine, exposing a layer or slice in a strange way. This happens regardless of whose mats I've dropped on a model; it doesn't seem to be a material-dependent artifact so much as something which simply happens, sometimes, when DoF is active.

I've observed this patterning in torsos, arms, and legs. Nonhuman figures and any clothing surfaces don't manifest this effect, that I've noticed. Only skin.

Note that when DoF is turned off, these patterns vanish. There is a 100% correlation between DoF being on, and these patterns appearing — when they appear at all.

Turning off DoF to get clean renders isn't really a desirable option here; there's a reason I use DoF, and it should be obious to any artist why I like having it available.

I don't have a whizbang NVIDIA setup, so Iray isn't a particularly practical choice for me; it always ends up doing a CPU render. I haven't noticed this effect in the Iray renders I've done. Just 3DL.

Has anyone else seen this and found a fix for it?