Hello everyone, I wrote this thread also in the openGL form. I think that also this form may help. If double threads are problem sorry. The mod can delete this thread. My problem is with getting the cursor position. I draw a quad with all vertex have a z value 0.25 and othe vertex values are (-1.0,-1.0) to (0.0,0.0). But when I click on the object I get cursor values (0 to 640, 0 to 480) which means the actual screen position. So a hit never happens when I try to make a selection. What can I do to solve this problem. PS : I use C#/CsGL and tried to understand the 32nd tutorial which is about selections. Thanks in advance and best regards.