Rendering with a spectral model of light and reflectance

We investigate a method for volume rendering using a spectral representation of colour instead of the traditional RGB model. Our framework provides a novel exploration of datasets through enhanced transfer function design. Furthermore, the technique of post-illumination is introduced to generate new spectral images for arbitrary light colours in real-time. To make sensible use of spectra in volume rendering, materials ( = reflectances) and lights are designed to fulfil special properties. In particular, we are looking for the following: 1. selective metamerism (two materials looking equal under one light and different under an other), 2. colour constancy (a material keeps its colour as the lights change), 3. metameric blacks (a material goes black under a specific light). Applied to spectral transfer functions, different light colours can accentuate or hide specific qualities of the data. In connection with post-illumination this provides a new degree of freedom for guided exploration of volumetric data, which cannot be achieved using the RGB model.