Why is emissive not emitting direct light like point light?

Development Rendering
1

Hi, I just want to know the background, why emissive materials are not casting any light on other objects around it? (aside from lightmass, dont want to use it)

I have this idea, where you can lit (kinda simulate GI) a room with just make every object emissive and tweaking the lights to look good.

Do I have an error in reasoning? Could it be possible?

Thx for your help and tipps.
Regards

2

First–for trying to do GI that wouldn’t work

But second, UE4 does not have dynamic lighting from emissive, that takes almost as much work as a full dynamic GI system.

3

I think you just answered your own question. This is a lightmass feature.

4

ok, to ask the question differently:

  • whats the difference between dynamic light calculation of one point light and lets say a cube emitting (single bounce) light from all 6 sides?
5

To be able to calculate shadows and bounce and have it look good takes a lot more calculation than realtime direct shadows from one light.