When I move RectangularLight with the gumball, the illumination of objects changes correctly, but when I rotate the RectangularLight with the gumball, Rhino ignores the rotation - the light widget is rotated, but the illumination does not change.
I tested it in rendered mode. You tested it in raytraced mode.
I tested it on this file:
rectangular light bug.3dm (132.2 KB)
Hello - In a rendered (openGL) viewport, rectangular lights are essentially point lights.
-Pascal
Yes, it is true, but it is a bug because Rhino documentation says: The RectangularLight command inserts a rectangular light object that emits light from an array of light points in one direction.
source: Lights | Rhino 3-D modeling
…and because the RectangularLight widget has an arrow showing direction of light rays.
When you flip the RectangularLight widget (by 180 degrees) you expect change in illumination, but there is no change.
The RectangularLight widget has an arrow showing direction of light rays. What is the purpose of this arrow?
Hi -
To point the rectangular light in the correct direction for a Raytraced display mode or full rendering.
-wim
If you flip the widget by 180 degree angle, its direction is still correct. If you program the renderer, you do not want to make light rays that are wasted because they slow down the renderer.
As a user, you need to decide in which direction to point your lights and which effect you would like to achieve.
-wim
1 Like
I love your picture - you have done your homework! 
You have proven that rendered and raytraced modes produce different illumination. It seems that they should produce the same illumination. The raytraced mode seems to be correct - there is no light emission from the back of the widget, but some light is scattered by the environment. In my opinion, there is illumination bug in the rendered mode.
Of course they aren’t going to produce the same illumination, they work completely differently.