What’s the step-by-step procedure to turn a mesh object into a light source? When I try, the ‘pick mesh’ button is greyed out.
Do you have “Mesh” option selected from the light type menu, if it’s on “Plane” the “Pick mesh” option will be disabled.
You need to switch to the Modify tab of the command panel. It is not possible to pick a mesh while still in the Create phase. This is an issue for many 3ds Max objects due to a limitation in the 3ds Max SDK.
Best regards,
Vlado