/// <summary>
/// Calculates a LineSegment from the camera's position to the
/// 3D position of the cursor, as if it were on the camera's farplane.
/// </summary>
public void CalculateCursorLineSegment(out LineSegment segment)
{
segment.start = Vector3.Zero;
segment.end = Vector3.Zero;
if (null == this.renderCamera)
{
return;
}
// Get position from Input Interface
InputInterface input = this.game.SceneManager.GetInterface(InterfaceType.Input) as InputInterface;
if (null == input)
{
throw new Exception("Input interface was not initialized before call to CalculateCursorRay()");
}
CursorInfo info = input.GetCursorInfo();
if (!info.IsVisible)
{
// Cursor is not visible, so we just bail
return;
}
// create 2 positions in screenspace using the cursor position. 0 is as
// close as possible to the camera, 1 is as far away as possible.
Vector3 nearSource = new Vector3(info.Position, 0f);
Vector3 farSource = new Vector3(info.Position, 1f);
MsgGetViewport msgGetPort = ObjectPool.Aquire <MsgGetViewport>();
this.game.SendInterfaceMessage(msgGetPort, InterfaceType.Graphics);
MsgGetProjectionMatrix msgGetProj = ObjectPool.Aquire <MsgGetProjectionMatrix>();
msgGetProj.UniqueTarget = renderCamera.UniqueID;
this.game.SendMessage(msgGetProj);
MsgGetViewMatrix msgGetView = ObjectPool.Aquire <MsgGetViewMatrix>();
msgGetView.UniqueTarget = renderCamera.UniqueID;
this.game.SendMessage(msgGetView);
Viewport vPort = msgGetPort.Data;
Matrix projMat = msgGetProj.Data;
Matrix viewMat = msgGetView.Data;
// use Viewport.Unproject to tell what those two screen space positions
// would be in world space. we'll need the projection matrix and view
// matrix, which we have saved as member variables. We also need a world
// matrix, which can just be identity.
segment.start = vPort.Unproject(nearSource, projMat, viewMat, Matrix.Identity);
segment.end = vPort.Unproject(farSource, projMat, viewMat, Matrix.Identity);
}