1) You can set the size of the surface drawn to in the D3DPRESENT_PARAMETERS which you pass to IDirect3D8::CreateDevice. You can also modify this with the IDirect3DDevice8::Reset call.

2) You use IDirect3DDevice8::SetViewport to specify the rectangle within that surface which gets drawn to. (After D3D transformation [the maths bit], x and y coordinates end up in the range -1 to 1, D3D then multiplies and scales them by the parameters set in the viewport). Setting the viewport would be the main part of your clipper code.

3) The Projection matrix determines how the x,y,z coordinates you pass to calls like DrawPrimitive get converted into the x,y coordinates in the -1 to 1 range handled above (interestingly enough the -1 to 1 range is called "**CLIP** space"). Most of what the projection matrix does is concerned with things like perspective - for a 2D engine, just use the D3DX functions to avoid the maths to set it up. Two useful parts the projection matrix has for your needs though is handling of the aspect ratio (scale in x and y directions and the ratio between the scales) and the offset for the coordinates. [D3DXMatrixPerspectiveOffCenterLH is probably the most suitable D3DX projection matrix generation function for your needs]

4) Some other calls like IDirect3DDevice8::Clear have rectangle parameters where you can specify the region to be operated on. [Beware though some graphics card drivers don''t like you clearing rectangles smaller than the screen with Clear]

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Simon O''''Connor
Creative Asylum Ltd
www.creative-asylum.com