Multiple vertex lights

Why would you divide by the total number of lights? All existing lights would become dimmer every time you add a new one.

The following code assumes you'll add a "source_strength" field to FDLight instead of using a global for light strength.

Function F3D_UpdateLights()
	For r.fdreciever = Each fdreciever
		;Calculate vertex colors
		s=GetSurface(r\ent,1)
		For i=1 To CountVertices(s)-1
			TFormPoint VertexX(s,i),VertexY(s,i),VertexZ(s,i),r\ent,0
			local intensity# = 0
			For l.fdlight = Each fdlight
				xd#=TFormedX()-EntityX(l\ent)
				yd#=TFormedY()-EntityY(l\ent)
				zd#=TFormedZ()-EntityZ(l\ent)
				dist#=Sqr(xd*xd + yd*yd + zd*zd)*radius
				intensity = intensity + l\source_strength / (xd*xd + yd*yd + zd*zd) ; ()=distance^2
			Next
			if intensity > 255 then intensity = 255
			VertexColor s,i,intensity,intensity,intensity
		Next
	Next
End Function

Implementing multi-coloured lights (r,g,b) should be trivial.