suppose i am looking at a circular disc placed on its flat edge with my line of sight on the same plane as the disc is lying. at this point, i should see a straight flat line. when i increase my angle of elevation, my line of sight is now at an angle from the plane in which the disc is lying (ie, i am slowly moving upward), i should gradually see a curve forming. what i am interested in knowing is that are there any algorithms that relate the angle of elevation to the curvature of the edge. Is it possible to get the coordinates of the curve formed with each angle of elevation? Have been searching the net for algorithms but nothing similar came up.

hi,
actually, i am trying to isolate the edge of the disc. at 0 deg, i will get a straight line, at maybe 5 deg, i get a slight curve, then at 10deg, another curve, but with greater amount of curvature. so i am trying to see if there is a relationship that defines how the angle of elevation will affect the curve u get. true, i can get it done in opengl, but i am really interested in knowing if such a relationship exists, or if some algo exists.

hi,
my mistake in referring to the ellipse as a curve, but that’s because I am only interested in the near edge, which should give me a curve. anyway, i am having a difficult time seeing why at 45 deg, u should see the minor axis with a length of radius/2. Here, I am assuming that when the person’s line of sight is elevated, it is along the y axis ie, the distance between the eye and the edge increases and does not remain constant as in moving in a circle. i thought there should be something that relates the curve u see, to the angle of elevation, but there seems to be nothing coming up.