Is this a simulation error? (about rect light)

RectLight isProjector(true) cone angle(30) position(0,0,1.866(sqrt(3)+1))
cube scale(1,1,1), position(0,0,0.5)

According to calculations, he shouldn’t have light shining down, but in reality, there will be a circle of light appearing at the bottom

I am not sure what you are asking. I do not understand your diagrams. A video would be better. You are saying the light is not working well ? First, turn off the other lights to see JUST the rectangular light influence. Second, if you need it to be super accurate then make sure you are running in path tracing mode. Also make sure the light in not intersecting the cube. That will not work.


I assume you are saying that you are trying to use math to make an EXACT size of light with a 30 degree shaping. Can you explain what you are trying to achieve? It looks right to me. You cannot have a light directly on top of an object and expect it to work. I do not understand what you are asking. Forget the math for a moment. What are you trying to achieve visually? You want to see a certain light cast on the floor at a certain distance ?

I want to calculate which positions in the scene will be directly illuminated by light and label them on the pixels of the image.
This issue does not have a significant impact, it’s just that I discovered this phenomenon during testing.