I have a windowing system in D3D8. Each window may contain zero or more child windows. I am using a MatrixStack and moving through the hierarchy and this is working beautifully except for one last thing. Say a window is 100 x 100 and has a child window 50 x 50. This child window is located near the lower right corner. D3D is drawing the entire child window. What I really want is to have it clipped to the parent window. I tried setting the viewport recursively much like I''m setting the MatrixStack. It posisions the child window correctly, but still draws the entire window just "shrunken" to fit the new viewport. I have no idea where to begin. The types of clipping I''m coming up with during my searches seems to be for much more elaborate types of clipping. Is there a simple, to the point way to clip these?