Question

I would like to get 2D screen coordinates of a 3D coordinates point with OGRE.
Is there any simple ogre function to do this ?

Thanks a lot.

Answer 1

I think there isn’t an OGRE function to do that directly, but you can obtain the same result with a minimal effort.

You have a 3D point, in world space, and you want to project your point into screen space. So, you need to multiply the point for the projection matrix and the view matrix, then you need to map the resulting point from coordinate space [-1 1] to [0 1].

For example:

Vector2 GetScreenspaceCoords(const Vector3& iPoint, const Camera& iCamera)
{
    Vector3 point = iCamera.getProjectionMatrix() * (iCamera.getViewMatrix() * iPoint);

    Vector2 screenSpacePoint = Vector2::ZERO;
    screenSpacePoint.x = (point.x / 2.f) + 0.5f;
    screenSpacePoint.y = (point.y / 2.f) + 0.5f;

    return screenSpacePoint;
}

Of course, if you want the coordinates relative to the screen size, you have to multiply the point for the width and height of the viewport.