c++ - OpenGL Rotation of an object around a line

Question

I am programming in OpenGL and C++. I know 2 points on 1 line (a diagonal line) and wish to rotate an object around that diagonal line. How can I go about doing this? I know how to use glrotatef to rotate it around the x, y or z axis but am not sure about this.

Answer 1

The x, y and z parameters to glRotate can specify any arbitrary axis, not just the x, y and z axes. To find an axis passing through your line, just subtract the end-points of the line to get an axis vector: if the two points are (x1, y1, z1) and (x2, y2, z2), the axis you need is (x2-x1, y2-y1, z2-z1).

Edit: As @chris_l pointed out, this works only if the line passes through the origin. If not, first apply a translation of (-x1, -y1, -z1) so that the line passes through the origin, then apply the above rotation, and translate it back by (x1, y1, z1).