I think I found a bug when on the objects properties in a scene we turn off both receive and cast shadows options.
If you do this and in the scene the other objects use glossy materials, the produce a very weird and strange artifact on their surfaces.
I am including an image and 3ds max scene if you need it. (2017)
Basically, in this simple example, the sky object has off both shadows options and the ground plane a reflection with glossiness.
Look at the strange oval dark shape here. If you change the glossiness value of the ground material, that shape changes as well.
I am not sure if this bug is related to the dimensions of the objects which are quite big, but imagine an exterior scene where the background plane is a background image applied on a tube or a plane…
If you miss some maps from the .max file I sent no worries, I forgot to turn off the Env. Overrides slots. In any case even with them off the problem is always produced here.
Looks like a couple of factors come into play here - e.g. if the plane material has no Diffuse, then the effect goes away. The dark area appears related to the area where the Sun is reflected on the plane.
The only way I could see to get around this was to use a CoronaLight material for the Tube object, which had to have Emit Light enabled, and Occlude Other Lights unchecked. (EDIT - which let me have Diffuse from the Sun, and Reflection from the Sun, and Reflection from the Tube, without the artifact appearing)
