Strange story!
I guess the speaker was covered with some kind of half transparent material through which the virtual visitor was viewing. You could have seen that in the 3D view except if that surface is very close to the point of view, because OpenGL requires the program to set an interval in the axis of view where objects will be taken into account and displayed (see viewing frustrum ), probably for performance reasons. SunFlow doesn't have this limitation and this may result in a different result for very close objects.
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Emmanuel Puybaret, Sweet Home 3D creator
