I have a function where I can calculate the point in 3D space given x & y screen co-ordinates below;
void Graphics::ScreenToWorld(float mousePosX,float mousePosY,float nDepth)
{
// Get matrices and the viewport.
D3DXMATRIX pm; // projection matrix
D3DXMATRIX vm; // view matrix
D3DXMATRIX wm; // world matrix
D3DVIEWPORT9 vp; // viewport
md3dDevice->GetTransform(D3DTS_PROJECTION,&pm);
md3dDevice->GetTransform(D3DTS_VIEW,&vm);
D3DXMatrixIdentity(&wm); // make the world matrix an identity matrix
md3dDevice->GetViewport(&vp);
// Call the D3DXVec3Unproject function twice to determine two points
// in our world space. Having two points we will be able to find
// a line in the world space. One point is for the z-near plane
// (which is usually z=0.0f) and another point is for z-far plane
// (which is usually z=1.0f). We grab the z-planes from the viewport.
D3DXVECTOR3 p1;
D3DXVec3Unproject(&p1, &D3DXVECTOR3(mousePosX,mousePosY, vp.MinZ), &vp, &pm, &vm, &wm);
D3DXVECTOR3 p2;
D3DXVec3Unproject(&p2, &D3DXVECTOR3(mousePosX,mousePosY, vp.MaxZ), &vp, &pm, &vm, &wm);
// We calculate an intersection of the line found previously
// with a plane z=0.0f. Equations of a line in 3-D space can
// be found on the following websites:
// http://mathforum.org...html#threelines
// http://mathforum.org...view/65721.html
// Here, wx, wy, and wz represent coordinates in the world space.
fWorldZ=nDepth;
fWorldX=((fWorldZ-p1.z)*(p2.x-p1.x))/(p2.z-p1.z)+p1.x;
fWorldY=((fWorldZ-p1.z)*(p2.y-p1.y))/(p2.z-p1.z)+p1.y;
// w is the point in the world space corresponding to the p point
// in the screen coordinates.
//D3DXVECTOR3 w(wx, wy, wz);
}How would I do the opposite? If I had a point in the word x,y,z - how would I get the screen co-ordinates for that point?
Any help would be greatly appreciated.
