A method for performing a volume rendering of an image uses a computer having a processor, memory, and a display. The method includes globally segmenting image data that represents an image to thereby locate boundaries in the image, determining regional opacity functions using the image data in a vicinity of the boundaries, and volume rendering the image data utilizing the regional opacity functions to display an image. The method provides a presentation of improved images of structures. These improved images are obtained using a regional optimization of the opacity function such that the perceived object boundary coincides more closely with a segmented boundary.