The invention relates to a method and device for generating and presenting an image on a visual display unit or some other display member. The image is composed, for example by an operator via a keyboard, of a plurality of symbols defined in advance in a symbol memory, which are placed on the image adjacent to each other. Each symbol is associated with at least one predetermined entry point and at least one predetermined exit point. When creating the image, a symbol is placed so that an entry point of that symbol is located immediately adjacent to an exit point of a previously displayed symbol.

A method of generating a line part having a thickness D on a homogeneous raster, in which the raster points are arranged in a number of parallel lines, and in which the bit representation of the line part is stored in a word-oriented bit-map memory in the form of a large number of image points or pixels. The method provides for making a determination of the envelope of the line part and imaging the envelope on the raster points. Thereafter, determining the length of the section through the line part for successive raster lines, and placing the bit representation of said lengths in the bit-map memory at corresponding locations, so that the direction of the determined lengths corresponds to the word direction of the bit-map memory.

Cumulative translational sweeps are used to shape geometric objects in a computer model, and they permit display of the resulting changes in shape in the object modelled, and control of processes involving the object modelled. If the geometric object is polyhedral, the cumulative translational sweeps, by creating additional facets, effect selective rounding along model edges and around model vertices. This permits computer modelling of the growth of layers, encompassing in addition to flat surface growth, growth with rounding around corners and over obstacles. Such growth occurs in the manufacture of semiconductors. Modelling a change in a solid structure in stages of growth (or shrinking) and of rounding, as might take place during processing of integrated circuits is achieved by controlled sweep sequences that sweep the structure a finite number of times in accordance with a rayset and stipulated parameters of shape, balance, convexity/concavity, degree of faceting, and memory limitation. The cumulative translational sweep (CTS) is applied in combination with Boolean operations to simulate growth and shrinking over the boundary regions of polyhedral models. By creating additional facets, it effects stipulated selective or global rounding effects along model edges and around model vertices. Such sweeps are examined in terms of Minkowski sums--of the geometric objects that are swept, with structuring geometric shapes that are convex polyhedron from the zonotope subclass of the mathematical family of objects known as polytopes.

A digital address filter is provided which converts straight-line and arc analog stroke data into digitized images which comply with Bresenham raster display criteria and can be displayed on a raster scanned monitor or LCD. Data collected over a preselected (M pixel.times.M pixel) spatial window are repetitively matched against a set of pixel template patterns permitted by the Bresenham criteria. After each full-frame iteration, the display pixel(s) corresponding to the best-fit templates are lighted.

A method is provided for increasing the speed at which a graphics image is displayed on a raster, such as in a liquid crystal display. The method incorporates off-line created look-up tables which are stored in memory means associated with a graphics processor unit. Thus, real time calculations are reduced resulting in a faster graphics image response time.