[HOpenGL] light sources.

[Patrick Scheibe]

The tutorial is fine but doesnt help me. Following (too simple) problem:
I want to look at a rotating cube. What happens is, that I'm rotating around 
the cube. That means the cube looks sometimes dark and sometimes bright like 
the day and nightside of a planet.

I've read the lighting part of the OpenGl-Redbook. They write that you have to 
put the "light position"-function different places to get different results. 
This seems totally intuitve and clear to me. E.g. to put it after a 
translation in the displayfunc produces a translation of the light source...

But in my code the  "position (Light 0) $= ..." call doesnt do anything.
It doesnt matter where I put it in the code and it makes no difference what 
position in my room the lightsource gets. Everytime the animation looks equal 
to that before.

I think I've forgotten something really important or some calls are not on the 
right place. Here is my code. The lightposition-call isnt in there but I 
tried every possible position in the code. The light-stuff is stolen from one 
of the GLUT examples. This example looks fine but doesnt have any animation.

<haskell>

myinit = do
   lighting $= Enabled
   light (Light 0) $= Enabled

main = do
  ...
  initialDisplayMode $= [GLUT.Double, GLUT.RGBA, GLUT.Depth]
  ...
  myinit
  ...

myReshape :: ReshapeCallback
myReshape size@(Size w h) = do
  viewport $= (Position 0 0, size)
  matrixMode $= Projection
  loadIdentity
  perspective 60 ((fromIntegral w)/(fromIntegral h)) 0.01 100.0
  lookAt (Vertex3  0 0 5)
	 (Vertex3  0 0 0)
	 (Vector3  0 1 0)
  matrixMode $= Modelview 0
  loadIdentity


myDisplay :: IORef GLfloat ->DisplayCallback
myDisplay arg = do
  angle <- readIORef arg
  clear [ColorBuffer, DepthBuffer]
  matrixExcursion $ do
    rotatef angle (Vector3 1 1 (1::GLfloat))
    stdCube
  swapBuffers

</haskell>

I dont know if this mailinglist supports atachments but here to pics of this 
cube at day and night :-)

Greetings
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