AWOLism wrote:Is that really physically correct?
If (and that's a big if) you have a light source that only emits in a cone, and produces no light whatsoever outside the cone, then yes, it's physically correct that you can't see the light source when your eye is outside the cone.
However I don't think there are many light sources like that in the real world. A flashlight, for example, must emit some light at near 90 degrees, because you can see it from that angle, even if your face is not illuminated. The key is that if you can see the light, your face (or camera) must be being illuminated at least a little bit. So if you want to see the light source at all angles, it needs to radiate at least a little bit of light in all directions.
So the lack of realism here is caused by the spotlight distribution not matching what you get from most real light sources, rather than the actual lighting calculations in the renderer being incorrect. You would see a result like this in the real world if the light source was a lightbulb inside a long tube coated with vantablack, or something.
There's no easy way to just control the visibility of the light source, because Octane only simulates the physical behavior of light - if there is no light coming to the camera from a certain direction, the corresponding pixels can only end up black. The solutions are to either make the light source emit some light towards the camera, or to add the light source in post.