Cycles: Edges around emission face

Hi,
I was messing around, creating a “cornell box” when I noticed quite jagged edges around the light source which just look wrong. Is there any way around it? The room is a box with the top face subdivided into 9 smaller faces and the middle face assigned an emission texture.

Thanks.


You could try setting the clamp value. It looks like the antialiasing is struggling with the high contrast from the light.

Thank you - will try that!

This has been covered before. (Don’t remember which thread though.)

Cycles has some problem with anti-aliasing when the light intensity value going to the camera is greater than 1. What is needed is a lightpath node to control the light from the emitter object. Output the camera ray on the lightpath node to a mixer controlling two emission values for the light. The top one (not camera ray) will be used at whatever value is needed to light the scene. The bottom one (camera ray) will be set with a strength level just under 1. That way the edges of the light emitter should calculate correctly in regards to anti-aliasing.

Here’s an explanation of why this happens, as well as a solution: http://blender.stackexchange.com/questions/17844/aliased-edge-around-light-source-in-cycles

Yesterday I had the same problem in reflections and now i stumbled over this thread… perfect timing and a simple solution - life is good :smiley:

This though won’t work when light reflects on glossy shaders or seen through glass because is just a workaround for the light visible straight to the camera. Better to clamp, raise white point in Color management and bring back mid tones with Curve imho.

such a light is not physically correct, it doesn’t exist.
what about an exr texture on the plane/light, some gradient B&W = dark edges?

Thanks all, esp. Greg. Good to get an understanding of why.

I always glare or glow such strong light sources (and their reflections if they are super-bright), that’s what would happen in a camera at least.

It’s funny reading on this kind of thing. Some older 3D software did gamma correction, and even Bryce had 48-bit dithering to help with colorspace stuff like this. (What it did internally was different for calculations than what it output to the screen. Made AA much better and prevented most color-banding.) But as in every case render engines are different, and some approaches that worked in one case might not be usable under differing conditions or are just simply a lost art.

Maybe in the future we’ll get something to better deal with this by default than doing a whole bunch of manual setting tweaks that require a tad of technical knowhow.