Limitations of Standard Volume Renderers Existing volume-rendering tools are designed with medical visualisation in mind. The objects of interest are solids and fluids which are purely absorptive. Many astronomical objects have poorly defined edges, in contrast to the well-defined boundaries between soft tissue and bone tissue in typical medical data. A further complicating factor is that many objects have signal only slightly above the noise level. However, even the traditional medical algorithms were far more effective in revealing structure than the techniques currently in use by astronomers.
Medical algorithms model a purely absorptive object with a background light source.
For astronomical data it is more appropriate to model the object as both emissive and absorptive, with no background light source. Often, artefacts of the processing are seen as faint streaks in the data, which may alert the astronomer to problems in the processing stages. Another limitation of standard volume renderers is the lack of analytical software. While in many cases medical specialists are content with viewing a region of the body as a whole, relying solely on inspecting images visually, the astronomer examines the data visually to guide their quantative analysis. Once a feature is identified in a multi-channel data set, quantitative measurements are required to determine the physical processes at work.