For Graphics I need to model the shape and the radiance profile of an existing light bulb in order to use it in a ray-tracing application. I can freely choose the light bulb. The strategy must not be very detailed or very long, just a few lines. As most light bulbs don't offer the radiance profile, I wondered how to construct it from the given specifications. I'm allowed to make some assumptions.
It would be of great help, if someone can guide me in a good direction.
If the bulb was a perfect diffuser, each point on the light bulb would scatter all the light that struck it uniformly over a hemisphere. The surface of the bulb would appear uniformly bright. This would be the simplest assumption.
If the bulb was perfectly clear, there would be no scattering. Light would travel in a straight line from the filament. The part of the surface between the filament and the observer would appear very bright, and the rest would not be visible.
The reality is between the two extremes. You would have to measure the radiance to find anything concrete.
If this matters, you could just assume it is somewhat brighter in the center and make up some smooth curve. Try some until your graphics looks good.
Since you can chose the bulb, chose something convenient. The spectrum of Flourescent and white LED bulbs depend on the phosphors used, which can vary considerably between models and may be hard to find specs for.
I'd chose incandescent because those are basically just black body radiators. Pick a plausible color temperature for a incandescent bulb and model that. For ray tracing, that generally only means finding the red, green, and blue contributions, however you actually define those.
You can get the CIE coordinates for any particular black body temperature directly from most CIE diagrams. Again, pick a plausible temperature for a incandescent bulb, and convert from the CIE coordinates to whatever you are using.
