Hello, Lesson 32 describes the picking mechanism, but my question is: Is this OpenGL mechanism accelerated by the 3D display cards? Is it worth to replace a mathematical approach for computing intersections? Example: testing if a line has an intersection with a triangle can easily be made with the Picking once we know two points on the line (one will be the position of the viewer, the second will be the direction to look at). If the instruction "glRenderMode(GL_RENDER)" returns 0, we know the line and the triangle won''t intersect. To your opinion, is this a good application of the Picking or am I completely gone insane?

I''m not sure about this, but I think that it would be VERY much faster to calculate it yourself.

gluunproject calculates a direction vector from your eye to the point on the nearclippingplane you clicked at
and then just do your line object intersection test

thats pretty much all you have to do

Picking is not accelerated.