2.1. Pixel pipeline

Pixel pipeline architecture.

The pixel rendering pipeline or short pixel pipeline renders 2d bitmap images from several multidimensional scalar data sources. It can produces several kinds of images, amongst others: grayscale, rgba, alpha-modulated, and colortable images. Each image type needs up to four scalar data sources as input, for example one source for each channel (red, green, blue, and alpha) in case of a rgba image.

Furthermore, these images can be combined into a stack using alpha blending with an image of the rendered stack as output. A schematic of the pixel pipeline architecture is shown in the above Figure. The visual properties of one image are contained in a layer object and a ordered stack of layers is organized in a LayerStack. They serve as a rendering blueprint used in image pumps. A image pump takes the blueprint together with the data sources and renders a 2d image. Internally, a image pump consists of subcomponents that take care of slicing through the correct axes of the multidimensional data sources and the blending of several layers into a stack image. Furthermore, several image pumps can be connected to the same layer stack and data sources allowing to render different slice views simultaneously.

The pixel pipeline is a lazy data flow processing pipeline, that is, subregions of images can be requested from the pipeline and only the calculations necessary to complete the request are actually performed.