Area Lights

I implemented area lights by giving the respective light a shape object as a child. I found an issue with this approach that I have not been able to solve: If the shape child is actually an instance, it can have a transform. If the transform scales the object, this scaling would normally influence the PDF, since it is proportional to the surface area of the shape. But I did not find a reliable way to automatically scale the PDF accordingly. Therefore, I gave the area light an extra scale parameter that allows it to re-scale the PDF as long as the scale applied to the instance is uniform. This has the unfortunate consequence that the scale factor has to be set twice, but I did not find a better way to do it.

An area light is actually used in my render in a very subtle way to guide the viewers eye towards the fractal by illuminating it a tiny bit.

The left image shows the render without the area light. On the right image, the area light applies a soft glow around the Mandelbulb.