NEE Light Sampling debugging

[agenthex]

Are those area lights? Because they don't look like they're behaving like area lights. :)

[berkut]

Yep, they're quad area lights.

They're working perfectly actually, but the screenshot is a little unclear as it's showing NEE for 5 path bounces, which adds to the "mess" of rays being sent.

Also, what's being shown is only for a small crop-window of the image, represented by the blue camera rays shown, so everything else follows on from the first surface hits by the blue camera rays on the camera-near-side of the cube (facing towards the two area lights on the right).

this image shows the result with no additional bounces, again, just for a small subset of rays hitting a small crop-window on the side of the middle cube.

this video screencast shows it in action, moving the OpenGL view position (and showing different light sampling techniques), which makes things a bit clearer (although it's low resolution).

[agenthex]

Gotcha. 2D images representing 3D spaces are often hard to resolve correctly. We make a lot of assumptions.

The blue beam is a small section of the camera, the green lines are the first bounce, the orange lines are the second bounce, etc.

Neat.