1. A method of adaptive maximum intensity projection ray casting, comprising: fragmenting a sampled 3-D dataset of a scalar field into a plurality of sub-volumes of different sizes, each sub-volume associated with a set of data value parameters characterizing the data value distribution of the scalar field within the sub-volume; defining a screen transfer function that is dependent upon data values of the scalar field; selectively casting a plurality of rays towards the sampled dataset, each ray having an initial data value record and a cross-section; for each ray, selecting a subset of the plurality of sub-volumes that are located along a path of the ray; identifying the maximum data value on the ray path that is within the selected subset; and converting the maximum data value into a pixel value in a 2-D image plane according to the screen transfer function; and using the pixel values determined for the cast rays to estimate other pixel values at other locations in the 2-D image plane.