Visualization Glossary
brightness: Subjective descriptor of color sensation encoding the notion of intensity.
elastic scattering: Light is scattered in such a way that no photon energy is lost. As a consequence the wavelength is unchanged. In the case a photon has lost some energy we speak of inelastic scattering.
emission: The process of evoking photons when a fluorescent molecule jumps from its exited state back to its ground state.
excitation: The process of bringing a fluorescent molecule in its exited state by absorption of light (photons).
fluorophore: Material composed of fluorescent dye molecules, or the dye molecule itself.
gray value: value of the element in the image matrix (see pixel).
inelastic scattering: Light that scatters inelastic losses energy. The scattered light has a longer wavelength.
iso data surface: An surface consisting of points with the same intensity. Because the data set is discrete, these iso data points are interpolated. The resulting smooth surface is typically located inbetween the discrete data points.
isotropic light: The light energy is equally distributed over all angles.
multi-valued volume image: Microscopist call this a multi-channel image. Different fluorescent dyes are assigned to each parameter of a voxel.
object labeling: Each object is identified by a unique number.
physically realistic image: Image formation is governed by accurate modeling of a physical process of light interactions with matter. In FluVR this process is inelastic scattering. The inelastic scattering is modeled by taking the data set as a distribution of fluorophores, with specific excitation and emission wavelength assigned to each type of fluorophore. Visualizing images obtained by confocal fluorescence microscopy leads as a matter of course to the physical model: fluorescence.
pixel: A digital image is actual a matrix of picture elements where the row and column indices identify the position of the element and the value of the matrix element identifies the gray level of the picture element. A picture element is abbreviated to "pixel" or "pels".
pivot: Look-up table that translates a certain parameter value into an other related value.
raytracing: A rendering technique to create realistic images by calculating the paths taken by rays of light that enter the observers eye. The single paths are traced backwards from the viewpoint. On its travel they may find objects that absorb and reflect the rays. All the parameters of the light source like intensity and color and how reflective or absorbent the materials of the objects are part of the model.
rendering: Adding three-dimensional qualities such as shadows, color and shade variation to obtain realism in computer graphics. Rendering techniques are for example the ray tracing process and the process using the SFP model.
segmentation: Subdivides an image into its constituent objects to a level that objects of interest have been isolated.
texture mapping: Technique where 2D images are pasted onto polygons. Usually, the images contain RGB color values and a transparency value denoted by (alpha).
volume image: A volume image represents a physical quantity as a function of three spatial coordinates. In a digital volume image, each sample (voxel) represents this quantity measured at a specific location. The image is made by a spatial sequence of 2D slices that include the object of interest. A slice is represented as an image matrix of pixels (x and y co-ordinates). The slice number indicates the z-coordinate. See Three Dee Image.
VoXel: Sample representing a physical quantity.
voxel value: A voxel value represents the weighted average of a certain physical quantity over a volume.