问Libgdx在2d中计算PerspectiveCamera视图

EN

private final Ray tmpRay = new Ray();
private final Vector3 tmpVec = new Vector3();
private final Rectangle visibleTilesRegion = new Rectangle();

private void updateVisibleTilesRegion (){
    // Define a ray that is a projection of the direction the camera is looking onto the 
    // tile plane (assuming it is a Z=0 plane).
    tmpRay.origin.set(camera.position.x, camera.position.y, 0f);
    tmpRay.direction.set(0f, 1f, 0f);

    //Find top and bottom
    Intersector.intersectRayPlane(tmpRay, camera.frustum.planes[4], tmpVec);
    float yTop = tmpVec.y;
    Intersector.intersectRayPlane(tmpRay, camera.frustum.planes[5], tmpVec);
    float yBottom = tmpVec.y;

    // Find left and right at the top of the screen by intersecting that line with the left 
    // and right planes
    tmpRay.origin.set(camera.position.x, yTop, 0f);
    tmpRay.direction.set(-1f, 0f, 0f);
    Intersector.intersectRayPlane(tmpRay, camera.frustum.planes[2], tmpVec);
    float xLeft = tmpVec.x;
    tmpRay.direction.set(1f, 0f, 0f);
    Intersector.intersectRayPlane(tmpRay, camera.frustum.planes[3], tmpVec);
    float xRight = tmpVec.x;

    visibleTilesRegion.set(xLeft, yBottom, xRight - xLeft, yTop - yBottom);
}