Using projectors instead of lights - modifiing Shader to look light lighting

Unity Engine
1

ADMIN-NOTE: Please move to Shader-Forum. Sorry for wrong category =/

Hey guys,
my game has a lot of lights on screen at the same time (traffic lights, to be specific) which can switch colors and therefor are dynamic. Until now I have used spotlights for that purpose, which beautifully illuminated the area in front of the light, drawing a nice little light cone. It worked fine on my PC, but testing it on my mobile device showed that most of the lights are being ignored.
So I thought about using projectors instead. I set one up following a blob-shadow tutorial. Naturally, the projected image looks like a colored shadow - instead I want it to appear like a light, brightening the area up instead of darkening it. I know that Unreal SDK provided projectors like that. Does Unity? You kind find the currently used shader code below.

Shader "FX/Projector Multiply" { 
	Properties {
		_ShadowTex ("Cookie", 2D) = "fresnel.png" {
			TexGen ObjectLinear 	
		}
		_FalloffTex ("FallOff", 2D) = "fresnel.png" {
			TexGen ObjectLinear	
		}
	}

	Subshader {
		Pass {
			ZWrite off
			Offset -1, -1

			Fog { Color (1, 1, 1) }
			AlphaTest Greater 0
			ColorMask RGB
			Blend DstColor Zero
			SetTexture [_ShadowTex] {
				combine texture, ONE - texture
				Matrix [_Projector]
			}
			SetTexture [_FalloffTex] {
				constantColor (1,1,1,0)
				combine previous lerp (texture) constant
				Matrix [_ProjectorClip]
			}
		}
	}
}

Cheers

2

Projectors are not terribly efficient, they duplicate every face they ‘shine’ upon, if your scene has 10,000 triangles, if you put a projector in, suddenly you have 20,000 triangles, with a few ‘lights’ this might be too much for mobile.

3

Thanks for that advice. My game is sort of tile-based with most of the tiles (each of which is appr. as big as the projector distance) having around 10 faces. So projectors should still be possible.
The question how to make the projector illuminating instead of shading still remains . Considering hpjohns advice: Is there a good alternative to spotlights (only limited amount) and projectors (performance issue)? Using “only” halos to indicate the current color is not really what I would call especially beautiful…