How to handle thousands of lights

Question

I'm trying to create a night-time city in Blender 3.2. For streetlights I've tried two approaches with geometry nodes:

• Instance lots of balls with an emissive texture.
• Instance actual point lights.

Neither does much in Eevee. Emissive materials don't light surfaces. With more than 128 point lights they get ignored. Cycles is slow in both cases.

I wonder if there is a clever solution? Can I somehow bake this lighting so the roads and buildings get a fast lightmap texture? I want to animate some stuff, but the lights and buildings will be static.

Answer 1

Here is a dark city scene setup with emissive materials for the windows and emissive spheres used as street lamps (EEVEE)

As you noticed, the emissive lights do not cast light on the surrounding objects - to do this in EEVEE, you will need an Irradiance Volume. Scale the Volume to your size requirements and bake the lighting in the render properties tab. You can adjust the cube-map size if you need better resolution (right side)::

You can also select the Irradiance properties and change the resolution - don't go too high or performance will suffer:

Here is the scene after the bake - the lighting will stay the same until you delete the lighting cache or bake again: