New subject: DDRAW: ComputeSphereVisibility: Am I in the good way?

13 Nov 2008


      I need to use some functions implemented in d3dx8 to do the job.
Can I link this dll to ddraw (even if it is not logical in a Windows point of view) or I need to reimplement all the needed math functions in wined3d?
David 
--- En date de : Jeu 13.11.08, Henri Verbeet hverbeet@gmail.com a écrit :
De: Henri Verbeet hverbeet@gmail.com
Objet: Re: DDRAW: ComputeSphereVisibility: Am I in the good way?
À: jeremielapuree@yahoo.fr
Cc: wine-devel@winehq.org
Date: Jeudi 13 Novembre 2008, 16h13
2008/11/13 paulo lesgaz jeremielapuree@yahoo.fr:
...
Hello
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,
Let Visibility=0
    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?
David
The basic idea sounds about right. I don't think you need to project
the sphere onto the frustum planes, just using the plane normal to
calculate the distance to the sphere center should do.