Do many projectors affect performance much?

Does using many projectors in Unity decrease performance of the computer by much? Say, if I am using a projector to cast water ripples decals on water surface when a character is in water, the ripples grow out of the center of the character, so there are 4 ripples drawn at a time so 4 projectors are needed, and if 4 characters are in water, that will be 16 projectors. Is that too much as to affect framerate, especially on mobile? Or is there a more efficient method? The water surface is wavy, BTW.

 

16 decals is probably not an issue unless the textures are very high resolution. Even then, I think you'd just find that some decals wouldn't draw at all if you go over your decal budget.

Take a look at page 65 of this slidedeck:

http://advances.realtimerendering.com/s2018/Siggraph 2018 HDRP talk_with notes.pdf

It shows the performance of having many decals in your scene. You can see that even with hundreds of decals, the performance hit is pretty minor.

So, for 16 decals, probably not something you need to worry about.