   Fast Object selection in 3D Scene
  Hello Friends,I am now facing a problem . It is about selecting objects in a 3D scene.In my scene i need to move object when the user clicks the axis ( local axis of the object x,y and z). So when mouse pointer comes around the axis i need to highlight the axis ( For a better user experience) .I am developing this program using opengl . OpenglGl pciking is slow.Any other good methods ? Thanks in advanceKD   
  Most physics engines (or collision detection libraries) have very fast routines for testing if a ray (3d line) intersects with an object. There are free physics engines you could use to do this.Otherwise you could program a picking test yourself (although I wouldn't recommend it when a physics engine can do it for you). Topics to research include converting a screen-space point into a world-space ray, and how to find the intersection-point between a ray and a cylinder/sphere/box/triangle.   ;  Thank you Hodgman .I would like to write my own. I look the idea given by you.;  Just test the ray for collision with a bounding box or bounding sphere.  Both are easy to do and require just a little math.   ;  There is another method, but nobody likes it.It involves assigning unique 32 bit IDs to each objects in the scene, rendering them without any shading, aliasing, just pure flat colour fill, using the 32 bit ID as the colour. Then looking at the colour of the pixel underneath the position of the mouse cursor will give the object id.But really, ray-cast from the scren to the mouse cursor, and do ray-intersect tests with bounding boxes, bounding spheres should be enough. There is a function in OpenGL to convert a 2D screen coordinate into a 3D coordinate (gluUnProject / gluProject?).   