Ray Tracing Overview - Unreal Engine 4.22 Preview

[Pixeldamage]

@Slayemin

I know exactly what this is. You’re running into floating point precision problems. The farther a float moves from 0, the less precise it gets because you need to use more bits to represent the exponent and you are limited to 32 bits with a float.
Single-precision floating-point format - Wikipedia

If you were writing the ray tracer code and wanted to “fix” this, one thing you could do is change all your floats to doubles, but that only kicks the problem further down the road. Another thing you could do is perform a behind the scenes origin shift on all objects in your world when the player reaches some threshold value on their X, Y or Z axis.

Thanks, yeah that was our hunch as well. I’m going to be rendering to 32bit EXR for world position pass AOVs so will also check that path tracer issue. Unfortunately the PT has other issues (at least in our custom build) where certain lights turn off when enabling it and strangely, the lights flip on/off states on each re-toggling. I’ve tried moving the lights to new sub-levels but have yet to pin down the issue.

The hybrid renderer doesn’t have this issue but it doesn’t seem possible to match the unbiased renderer at this point (even when realtime isn’t a goal).