1. Field of the Invention
The invention relates to a method for displaying continuous lines on a raster-based display appliance, with a continuous line being defined by a sequence of two-dimensional support points and a line width, and with a rectangle, which connects each of the support points, having a rectangle length predetermined by the distance between the support points and having a rectangle width predetermined by the line width being displayed between two support points.
Raster-based display appliances are used, for example, in vehicles or aircraft, and are used to display information which is important for operation and/or control of the vehicle or the aircraft. The respectively displayed information is intended to be displayed as clearly as possible, as well as quickly and in an unambiguously identifiable manner, on the display appliances that are used, normally screens or flat displays. At the same time, undesirable changes during the display of the information, such as line thicknesses which vary as a function of orientation or position or continuous lines which are interpolated uncleanly are intended to be avoided, since they could disadvantageously distract the viewer.
2. Discussion of the Prior Art
In order to allow graphics displays to be produced and displayed in particular in aircraft which are intended to comply with stringent quality demands because of safety-relevant requirements, programming languages and hardware components matched thereto have been developed, which are distinguished by simple but reliable reproduction, as naturally as possible, of visually displayed information. While the software, such as the “Standard Graphics Language” (SGL) is being developed further all the time, the development of new hardware components is extraordinarily costly, particularly for civil and military aviation.
In order to make it possible to avoid the development of hardware components with ever greater performance, which are optimized for displaying such information, methods for displaying graphics information are being developed, and/or optimized, which do not require any hardware components matched thereto and, for example, can also be used in conjunction with commercially available graphics cards, graphics processors or graphics display appliances and at the same time allow and ensure high-quality graphics display.
It is known from practice that a continuous line which is defined by a sequence of two-dimensional support points and by a predetermined line width can be represented by a sequence of rectangles which connect respectively adjacent support points to one another and whose widths correspond to the predetermined line width. If the standardized graphics programming language OpenGL is used, then the rectangles are each preferably displayed as two triangles with a common base line, since, in this graphics programming language, triangles and triangle sequences can be produced and displayed particularly quickly.
However, rectangle sequences such as these are subject to a problem with regard to the area between two successive rectangles, if the mutual alignment of the two successive rectangles differs noticeably, and is at an angle α. In this case, the two successive rectangles partially overlap while a visible gap remains on the side opposite the overlap area, which gap is not covered by either of the two successive rectangles.
A continuous line composed of a plurality of rectangles is then no longer perceived as a uniform continuous line displayed naturally, but rather as a discontinuous line, for example as a sequence of individual line segments, which do not appear to be continuously connected.
By way of example, US 2007/0 222 784 A1 has disclosed the possibility of covering or filling the resulting gaps between the rectangles with circular segments in order to give the continuous line a more natural appearance. In this case, a check is carried out for all the pixels which could fall in the area of the circular segment to determine whether and if appropriate with what intensity the relevant pixels should be displayed. A method such as this is highly computation intensive and, in particular, is unsuitable for displaying numerous continuous lines with a line width comprising a plurality of pixels.