Light Intensity is an inverse square:
I = 1 / r^2

For GE/PD we would need to use a Multiplyer since this equasion dies at 5.

I = Intensity (0-1) 
r = (d)istance between vert & source [See Appendix Below]
MULT = Multiplyer
S = Saturation

So the Equasion is as follows:

I = 1 / (d / MULT + 1)^2

I = I * (cos x)

S = S * I


Example:

                Z_____Q
               /        \
   O----------x------------Y
     
      \       |         /
        \     |      /
          \   |   /
            \  /
              L

L=0,0,100
x=0,0,0
y=100,0,0
O=-100,0,0
Z=10,0,-10

LX = 0 Degrees 
LY = 45 Degrees
LO = -45 Degrees
------------------------------------------------
LX:
MULT = 1000

I = 1 / (d / MULT + 1)^2
I = 1/ (SqRt( (x2-x1)^2 + (y2-y1)^2 + (z2-z1)^2 ) / MULT + 1) ^2
I = 1/ (SqRt( (0-0)^2 + (0-0)^2 + (100-0)^2 ) / 1000 + 1) ^2
I = 1/ (100 / 1000 + 1)^2
I = 1/ (1.1)^2
I = 1/1.21
I = 0.83

I = I * cos0 
I = 0.83 * 1
I = 0.83

S = S * 0.83

--------------------------------------------
LY:
MULT = 1000

I = 1 / (d / MULT + 1)^2
I = 1/ (SqRt( (x2-x1)^2 + (y2-y1)^2 + (z2-z1)^2 ) / MULT + 1) ^2
I = 1/ (SqRt( (0-100)^2 + (0-0)^2 + (100-0)^2 ) / 1000 + 1) ^2
I = 1/ (1.14)^2
I = 1/1.30
I = 0.77

I = I * cos45 
I = 0.77 * 0.71
I = 0.54

S = S * 0.54

--------------------------------------------
LO:
MULT = 1000

I = 1 / (d / MULT + 1)^2
I = 1/ (SqRt( (x2-x1)^2 + (y2-y1)^2 + (z2-z1)^2 ) / MULT + 1) ^2
I = 1/ (SqRt( (0--100)^2 + (0-0)^2 + (100-0)^2 ) / 1000 + 1) ^2
I = 1/ (1.14)^2
I = 1/1.30
I = 0.77

I = I * cos-45 
I = 0.77 * 0.71
I = 0.54

S = S * 0.54

--------------------------------------------

Z & Q are behind xyo and so get no light.
Set to ambiant.




===============================================

Appendix of individual Equasions

- Distance between two points 3D

d = SqRt( (x2-x1)^2 + (y2-y1)^2 + (z2-z1)^2 )

- Intensity with Distance

I = 1 / r^2

- Intensity with angle

I = I * cos a