The following text comes from the OpenGL-redbook (ch5 about lighting, p137)) about glLightfv(GL_LIGHT0, GL_POSITION, light_position):
As shown, you supply a vector of four values (x, y, z, w) for the GL_POSITION parameter. If the last
value, w, is zero, the corresponding light source is a directional one, and the (x, y, z) values describe its
direction. This direction is transformed by the modelview matrix. By default, GL_POSITION is (0, 0, 1,
0), which defines a directional light that points along the negative z-axis.
I don’t quite understand this. If (0,0,1) is the direction, I would interpret this as pointing along the positive z-axis and not along the negative z-axis.
When I try this, the light however does indeed seem to point among the negative z-axis, and thus coming FROM the mentioned point and going to the origin instead of going TO the mentioned point from the origin. Am I mixing up coordinates or is it maybe ‘not that clearly documented’?
rob