   Intersecting a vector and a plane
  Hi,While check my frustum, I am wanting to check if the edge of the frustrum intersect certain planes.For instance, say I have a ground plane of ( 0,1,0,0 ) - ie, an identity plane - I am using D3DXPlaneIntersectLine to find where the frustum intersects.However, if I am looking up, I get a point behind the camera - not much use for culling!Can anyone suggest a more elegant way of finding frustum intersects of a plane IN FRONT of the camera.Thank you very muchSimon   
  What you call "vector" I call "ray". In order to have a ray you need to specify a point P and a vector V. Then all the points in the ray can be written as P+s*V, where s is a positive real number. Substitute P+sV in the equation of the plane and you'll get an easy first degree equation in s. If the equation has a positive solution, you plug s in P+s*V to get your intersection point.