I know how to set a light in OpenGL but I cannot quite figure out how to set a directional vector for it.
I whipped this up in AutoCAD to show what I mean. The view here is isometric to show how the light rises above the canvas then points back down at an angle. I've checked on line documentation but find it a bit confusing. Now I could be wrong but I think AutoCAD uses OpenGL to render in this old version so hopefully the effects will be transferable.
For directional lights you simply set the 4th component of the light's position to zero which will set it infinitely far away.
Wouldn't the lights have no direction if they were infinitely far away?
The light I need should rise above the drawing area and shine back down on the drawing. The drawing is what I want even though it was done in a drafting program. It is isometric to show how the light is positioned. By default the lights make everything appear fully lit because I assume the default view is parallel to the light source.
Even if it's at infinity you can still tell the direction (just like the sun), so all light-rays are parallel which is exactly what you want.
See here (http://jerome.jouvie.free.fr/OpenGl/Tutorials/Tutorial13.php) and have a look at homogenous coordinates (http://en.wikipedia.org/wiki/Homogeneous_coordinates).
GREAT thanks!
Have some karma.