This scene was created by Ole Lemming. He wrote:
"Light shines onto a white diffuse wall. Reflected light from the wall creates caustics through a glass
sphere. That is diffuse -> Specular(caustics). I got the idea for this scene from a document by Henrik
Wann Jensen describing some difficult test scenes. Not easy to achieve with some of the other renderes
on the market, but no problem for WinOsi :-)"
This scene also shows, that there is a problem in WinOSi - not in the diffuse to specular light
transport or the caustics - but the intersection edge between the floor and the wall seems to glow because
the bright illumination from the other side of the wall shines through.
You can avoid this problem by splitting the wall and the floor into two parts, leaving a small gap between
them (larger then one pixel (according to the pixel scan radius from the render dialog)).