   GluDisk collision detection??
  Is there any easy way to detect whether or not a gluDisk object is in the same place as another?of do you just have to compare x and y positions?   
  Do you mean exactly in the same place as in your post, or do you just want to know if two disks are touching or partially overlapping each other?   ;  just partially will do fine.   ;  Two disks overlap in the 2D plane if the distance between their centers is smaller than the sum of their radii, or:(x-x')² + (y-y')² < (R+R')²It is harder to check in 3D, though.   