How many light probes

Hi, How many light probes is enough? the reason I ask when I add light probes to my scene and use the scene view to navigate with the below amount it slows down to a crawl, should I just place one under each light and one in between each light ? Or do I need more, as I need to copy the light probes on this level and paste on another 3 levels.


This is rather an old question, but as it’s still something quite present without any approved answer, I’ll answer it.

How many light probes in a scene is a relative question based on the scene itself.

The common mistake many do initially is thinking that the light probes are helping with the baked lights for static objects. That’s a mistake as light probes are used primarily to determines the light on non-statics object that are “out” of the baked light process. Each light probes (when baked) register the light value at its position. Then non-static rendered object gets their lighting value from those light probes rather than from the static light. (Non static light don’t get their value stored.) It’s kinda like regrouping all the static light into singles points in a scene which help save calculation with the scene lighting for non-static objects. (In other words, instead of having multiples light sources to light each faces, you got 1 light probe that simulates said multiple lights.)

As such, in the example of the picture shown in the question, the number of light probes shouldn’t be high as the lighting isn’t highly variable. It could be done with 1 light probe in the center of the darkest areas and 1 light probe in the brightest areas and, if necessary, 1 in-between for the areas that might have a lot of stuff hiding lights (1 in-between vehicle and 1 over vehicles for example). If it would be possible to crawl (or have stuff roll) below a vehicle, it would also need on under it.

Not too sure about how Unity handles light probes yet- but I know from past experience with IDTech 3 engine (GTKRadiant/QuakeEditor) making COD4 MW mods; light probes are needed (otherwise the game is discolored), but recommended to be used sparingly for optimal frame rates. With Radiant, I usually placed one outdoors & one indoors usually near light sources-- that usually did the trick for small - medium maps…

I found this documentation when I was looking around for some info on how Unity implements light probes. Not sure how big the map is on the sample, but it seems like it needs a bit more than Radiant (sorry it’s my only frame of reference regarding light probes).

With your scene, I’d start with 5 (to be on the safe side, 1/corner & 1 in the middle of the room) & experiment from there.