Botha, Charl P.Post, Frits H.D. Ebert and P. Brunet and I. Navazo2014-01-302014-01-3020021-58113-536-X1727-5296http://dx.doi.org/10.2312/VisSym/VisSym02/071-076This paper presents a new technique for supplying meaningful visual feedback during direct volume rendering transfer function specification. The technique uses meta-data calculated during a pre-processing step to generate interactively an approximate volume rendering that is voxel-registered with a single user-selected slice. Because of the registration, this preview can easily be alpha-blended with a grey-scale image of the data that is being volume rendered. In this way, the user gets real-time visual feedback on her transfer function specification with regards to both the expected composited optical properties and the "fidelity" (how closely the rendering matches the original data) of the resulting rendering.