A Hierarchical Occlusion Culling Method Reducing Query Delay

There is provided an apparatus for sharpening ice skates, which includes means for supporting the blade in a fixed location, and means for moving a rotating grinding member along the blade, with the grinding member rotating about an axis parallel with the plane of the blade. The guide means are provided to allow the grinding member to follow a predetermined profile. The guide means include a gearing arrangement which rotates a cam shaft as the carriage supporting the grinding member moves longitudinally of the blade. A pivotal arm supporting the grinding member has a cam follower which is raised or lowered by the cam surface, to cause the grinding member to follow the predetermined profile.