# Lightmap generation

I’ve just added lightmapping to my engine but
lightmaps does not look perfect because I cant get my lumel lighting equation to work.Can anyone help?(I have position of lumel in worldspace, it’s normal, distance to pointlight and light’s radiur).

Can you give more details about “not perfect”?

Well, faces with lightmaps look nice but some of them are black even if distance to the light source is shorter than light radius. I use this equation:
Brightness = (1 - 1 / LightRadius * Distance ) * (cosAngle-0.5).

Here is mine:

Brightness=MIN (cos Angle*2.5 , 1 - 1.3 * Distance / Radius )

I’m also searching a better one

Y.

Isn’t the light intensity just the dot of
the face normal and the normalized direction
to the light, divided by the square of the
distance to the light? At least, I believe
that’s how physics works in general.

Then you apply the light function (i e
color, specular, etc).

I e if the point is P and the light is L and
the point normal is N, you’d get brightness
like this:

B = fL( N . Norm( L - P ) / ( | L - P | ** 2) )

(B = brightness, fL == light function).

Note that fL should probably return the
ambient value for negative arguments (i e
things facing away from the light).

Oh, and this argument to fL simplifies
reasonably well when you start writing it out
as coordinate operations. Especially the
| L - P | ** 2 part

Just copy the OpenGL lighting model and it’ll look good.
brightness = (1 / (c + d * length + e * length^2)) * dot(norm(L-P),Vertex_Normal);

where c,d,e are arbitrary constants.