"Bounding" shadows in IRay?

Ptrope

I'm seeing shadows on my floors in IRay that aren't of the objects themselves, but appear almost to be 'bounding box shadows' - but even then, moving the object seems to change the shape of the shadow. I'm seeing this on different materials and under different kinds of lights - environmental, spotlight, distant light, emissive lights.In these shots, the chair is on the floor in the first and second ones, -1 below it in the third, +1 above it in the fourth. allowing the render to continue doesn't eliminate it, and it's also present in the IRay prevue. This floor is a velvet material, but I've also seen it on plain surfaces and glossy, reflective surfaces. I'm finally starting to get the hang of Iray lighting - I hate to not be able to render anything because it has boxes on the ground below it.

Tobor

1. Do you have any hidden surfaces where you've set the Opacity Cutout to 0? This doesn't really hide the geometry. Under certain circumstances these surfaces can still influence the renders.\

You'd do well to experiment with a variety of other assets from alternate sources, just to make sure it's not an object/surfaces/material thing on your end.

2. Some unusual shadowing can occur depending on the resolution of the mash the light is falling on. The most common is referred to as shadow terminator artifact. The artifacting is a jagged or geometrical appearance caused by the underlying mesh that has a low resolution. The default Environment Dome virtual ground has no mesh, so artifacts won't show here. Try removing your ground pieces and look at the shadows on the virtual ground. Note that only certain types of light sources will cast a shadow on the virtual ground, so don't get frustrated by this. It's just for testing if the "boxing" appearance also occurs with the virtual ground.

3. If you find the weird effects go away when cast on the virtual ground, consider increasing the mesh resolution of your floor geometry. You don't have to go crazy with the resolution, but try upping the SubD if the geometry can support it.

Ptrope

Nope, no surfaces hidden using opacity settings - the chair is allpresent and accounted for, with only 3 materials: padding, upper body, pedestal. But it's not just the chair - it appears under the Genesis 3 figure, too. I've seen it under other figures, as well, male and female, clothed and not - the floor in these cases was either light enough to show the shadow 'boxes,' or as in this case, a solid color so it's obvious. It may appear in other renders, but the floors are an uneven texture or color, like a wood parquet, which may disguise the effect.

I'll try it on the 'virtual' ground - it's not much of a solution, though, if it appears on models, since they kind of have to be in the scenes ;).

Fishtales

It looks as if you might have the camera light on. Try switching it off and see if that helps.

Ptrope

Nope - headlamp is off; set to automatically go off when lights are in the scene. Even if it were on, it wouldn't cast those squared shadows directly below whatever is standing on the surface.

The shadows don't appear on the virtual floor. They don't seem to appear on the floor of the "Curious Hallway," but it has a lot of texture going on that may disguise it.

My latest experiments are using a simple checkboard floor I made several years ago - it's a Poser prop, imported without any material chages (it's interesting that the materials are all set to "0" for reflection, and yet ... ) After trying it with the same lights used in the previous shots, I subdivided the floor, raising the rez 8x. It seems that the rez of the floor may, indeed, have been the culprit! Good to know!