Question

I’m trying to implement a deferred shader with OpenGL and GLSL and I’m having trouble with the light geometry. These are the steps I’m taking:

Bind multitarget framebuffer
Render color, position, normal and depth
Unbind framebuffer
Enable blend
Disable depth testing
Render every light
Enable depth testing
Disable blend
Render to screen

But since I’m only rendering the front face, when I’m inside a light it disappears completely, rendering the back face does not work, since I would get double the light power (And when inside, half [or the normal amount]).

How can I render the same light value from inside and outside the light geometry?

Answer 1

If i remember correctly, in my deferred renderer i just render only the backfaces of the light volume. The drawback is you cannot depth test, you will only know if a light is behind a geometry after the light calculation is done and discard the pixel.
As another answer explained, you can do depth testing. Test for greater or equal to see if the backface is behind or on a geometry, therefore intersects with the surface of the geometry.

Alternatively you could check if you are inside the light volume when rendering and switch front faces accordingly.