I’m trying to export area lights from blender to Mitsuba 2. Mitsuba 2 area lights “strength’” is specified as the emitted radiance (W/m²/sr). Blender stores the emitted power of the light, so dividing this by the product of the area of the emitter and the solid angle of a hemisphere should convert from power to radiance. Rendering in mitsuba using this converted radiance gives however a different result, with the light looking too dim.
The exporter Addon for LuxCore Render corrects this by eyeballing a scale factor. Is the emitted power of an area light remapped in any way in Blender ?
Here are some threads that you might find helpful
Jon Lampel has made an absolutely excellent high-level video here:
These sorts of subjects are intimately wound up with pixel management and digital colour, which many developers / engines completely ignore the details of.
Thank you for your answers. However, it doesn’t really reply to my question, which concerns specifically area lights.
To illustrate, if you try to light a scene with a 1 m² plane with an emission shader or with a 1m² area light with the same strength, you would end up with different renders, the one with the plane being much brighter. However, one would expect them to behave in the same way, because the Power emitted by both lights is the same (in the interface). Even if you consider that the plane emits on a 2m² area (both sides) you still end up with a different result. Hence my question: is there some sort of remapping done for area lights? From looking at the posts @EAW mentioned, it looks like @brecht could answer that question.