lighting problem

sarahippo · September 10, 2003, 1:54pm

Hi,

I have a rotating cylinder.
The problem is that when I apply lightings on it, the cylinder gets darker and darker as it rotates, and eventually it becomes black.

why?

Sourpotato · September 10, 2003, 8:31pm

How do you place your light source position?hah

sarahippo · September 11, 2003, 9:58am

how should i place the light source?

Deiussum · September 11, 2003, 1:06pm

Probably a different way than what you do now…

Things to think about when placing lights that might help you figure out your problem.

glLightfv(…, GL_POSITION/GL_SPOT_POSITION, …) calls are affected by the current MODELVIEW matrix.
glLightfv(…, GL_POSITION/GL_SPOT_POSITION, …) calls are NOT affected by the PROJECTION matrix, so if you are putting things there that you shouldn’t be, like glRotate/glTranslate/glScale, your lighting calculations won’t work like they should.

1234 · September 11, 2003, 6:34pm

If things change over time, the problem is mostlikley that you dont use ‘glLoadIdentity’ or that your are messing with the matrixmode.

Both are common beginners mistakes.