a method for performing direct rendering of a multi - volume data , having the steps of determining whether a volume of the multi - volume data is one of active and inactive via interaction with a ray for the multi - volume data , recording in triplicate a starting point and an end point of the ray for an eyespace , repeating the determining whether the volume is one of active and inactive via interaction with a ray for the multi - volume data and the recording in triplicate a starting point and an end point of the ray for an eyespace for all volumes of the multi - volume data , providing triples from all volumes to an array , sorting the array to create a sorted triples list array , breaking the ray into a plurality of segments using the sorted triples list array , determining which volumes are active for each of the segments via an active volume list , and sampling each segment of the ray to acquire an accumulated result .