A method of point picking on a fused volume rendered view of multiple
registered volumes having the following steps: selecting a rendered
pixel, finding the projection ray through the rendered pixel, finding the
intersection segment of the projection ray with the fused volume,
traversing the intersection segment according to a traversing
intersection point, calculating the intermediate fused volume rendered
value at each traversing intersection point, evaluating a stop condition
at each traversing intersection point leading to a final fused volume
rendered value, outputting the coordinates of the traversing intersection
point where the stop condition was reached as the picked point.