Bubble With "light" material


I was trying to simulate a scene lit by an enclosing spherical shell, and tried to use the “bubble” geometry for that. However I got en error saying that bubble cannot work with “light” material. What’s the reason for that?


The “light” material, along with “illum” and “spotlight” are special insofar as they create light source objects in the scene that attract shadow-testing rays. There isn’t code to cover every possible geometric shape for this operation, which must be very efficient, hence this error.

You can apply “glow” instead of “light”, so long as you use a distance (fourth argument) is <= 0. This should work fine so long as you have interreflections turned on (-ab 1 or greater).

The more usual option is to use a “source” primitive rather than a bubble, giving an angular size of 360. Since your radiance is the same in all directions, this is physically equivalent to a bubble as seen from the inside. Again, you should use a “glow” material for this.