I recently include the cArcball class to my mfc application (a map editor) but i don't know how works the concept of the arcball. I know what the result do (saw mfc examples, lot of them use an arcball to allow the user to manipulate the 3d gfx) and i'v already included the code in my project... but the result shows a bug that i don't understand ; when i try to drag onto the image, the object seems to become mad and is rotating in every ways... This seems to be a problem with my interpretation of the values returned by the arcball... but i don't really know the concept of arcballs (pragramatically).. Do someone ever used this class, or knows how works an arcball ? Edit : After a little search, i founded some informations in this PDF file : http://www.daimi.au.dk/~mbl/cgcourse/wiki/_files/shoemake92.pdf ... if someone whant to know ! [edited by - Dzero on June 4, 2003 6:00:14 PM]