This seems like it should be a simple enough task, but it must be late because I am just pulling my hair out here trying to solve this. Basically all I want is: Given a world vertex at (x,y,z)... how do I get back a screen coodinate (x,y). Here''s what I am doing so far... I set up an object in my 3d world at say... (x,y,z) 800,0,500. Then positioned camera at 300,0,-1000. Taking a screen shot I grabbed the sx,sy (screen x,y) co-ordinates ~(550,300). Screen window is 800x600, with FOV=1.2, Aspect=1.33, NearPlane=1.0, FarPlane=5000. Step by Step... 1. Find World Matrix given 800,0,500: D3DXMatrixTranslation(&MatWorld, 800, 0, 500); W= [1 0 0 0] [0 1 0 0] [0 0 1 0] [800 0 500 1] 2. Get View Matrix (Camera): V= [1 0 0 0] [0 1 0 0] [0 0 1 0] [-300 0 1000 1] Thus, VW=VxW= [1 0 0 0] [0 1 0 0] [0 0 1 0] [500 0 0 1] , which is right object is 500 in x-dir from the camera. 3. Figure out Projection Matrix. I used call: Graphics->GetDeviceCOM()->GetTransform(D3DTS_PROJECTION, &matProj); or calculated using... w 0 0 0 0 h 0 0 0 0 Q s 0 0 -np 0 w = cot(fovw/2) h = cot(fovh/2) Q=fp/(fp-np) np = distance to near plane fp = distance to far plane Thus proj matrix is: P= [1.09 0 0 0] [0 1.46 0 0] [0 0 1.0 1.0] [0 0 -1.0 0] 4. Convert to Normalized Device (Screen) Co-ordinates (NDC) (-1.0 to 1.0) for x and y. 5. Convert NDC to screen sx, sy using projecyion matrix (#3). This I know how to do factoring in the FOV and Aspect ratio... Sooo where I really need help with is Step #4. How exactly do I get the NDC (screen x,y coordinates from -1.0 to 1.0). In other words how do I go from a 3d vertex (x,y,z) to normalized screen x,y?? Any help, links or suggestions would be huuugely appreciated... thanks in advance... rhuala

oh well look at that a function that already does what I''m trying to do, thanks Endurion...

What do you mean by "assure you don''t have a pure device".

I Usually read in the matrix as follows:

Graphics->GetDeviceCOM()->GetTransform(D3DTS_PROJECTION, &matProj);

How can I be sure I dont have a pure device??

rhuala

Is this dependant on your video card? Is it a good idea to stay way from the command GetTransform?

Does this reduce the compatibility of your program...