DDRAW: ComputeSphereVisibility: Am I in the good way?
jeremielapuree at yahoo.fr
Thu Nov 13 08:40:15 CST 2008
I would like to implement ComputeSphereVisibility. The sting game is completely black because of this stubbed function. Here is my idea to implement it. Am I in the good way, or it is completely a bad idea?
With GetViewport, I retrieve the viewport matrix V, and with GetTransform, I retrieve projection P and world W matrices ofn the device.
I multiply the three matrices in a matrice M: M=VPW
If M is singular, function returns with a failing message
Otherwise, with the matrix M I retrieve the planes of the frustum view (that's a little bit of math, but quite easy)
Then for each sphere,
for each plane of the frustum view
Let I be the intersection of the orthogonal projection of the center sphere on the plane.
If I is in the frustum view,
then I have the visibility.So
Visibility=Visibility|(flag for the visibility of the chosen plane)
Once I did it for the 6 plane, I have the visibility of the sphere.
Is it a good point of start?
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