E. Volume textures
In order for the graphics hardware to be able to access all the required volume information, the volume data must be downloaded and stored in textures. At this stage, a translation from data format (external texture format) to texture format (internal texture format) might take place, if the two are not identical. Usually and in many datasets we have working with this is the case, so the conversion or translation from data format to texture format must take place. This component is usually executed at startup, when the rendering mode changes, or when a new 3D data set is ready to be rendered. How and what textures containing the actual volume data have to be downloaded to the graphics hardware depends on a number of factors, most of all the rendering mode and type of classification. Proxy Geometry Rendering The last component of the execution sequence outlined in this section is getting the graphics hardware to render geometry. This is what actually causes the generation of fragments to be shaded and blended into the frame buffer, after resampling the volume data accordingly.