초록 ▼

A graphics system and method with which thick graphic primitives are efficiently drawn by minimizing dependence on drawing algorithms that require appreciable setup time. The method contemplates drawing a thick primitive in which an offset or displacement value is first calculated, based upon the th

A graphics system and method with which thick graphic primitives are efficiently drawn by minimizing dependence on drawing algorithms that require appreciable setup time. The method contemplates drawing a thick primitive in which an offset or displacement value is first calculated, based upon the thickness of the graphic primitive. The offset is approximately one half of the thickness of the primitive. Following calculation of the offset value, line drawing parameter values are determined for a line that is parallel to the origin line and displaced from the origin line in a minor axis direction by the displacement or offset value. A loop is then repeated for each grip point in the major axis range of the line. The loop includes an initial step in which a boundary pixel of the thick graphic primitive is drawn using the line drawing algorithm and the line drawing parameter values calculated for the offset line. After the boundary pixel has been drawn, one or more adjacent pixels are drawn using a stepping routine in which the mirior axis coordinate of the selected pixel is either decremented or incremented, depending upon the slope of the line, to write the pixels adjacent the boundary pixel. In this fashion, the present invention draws a thick primitive as a sequence of segments that are parallel to the minor axis of the origin line. In the preferred embodiment, the line drawing routine is preferably comprised of a Bresenham line drawing algorithm or a similar derivative algorithm. In the preferred embodiment, the displacement D is equal to FLOOR((W?1)/2), where W is the thickness of the primitive and FLOOR(X) is the integer portion of X.

대표청구항 ▼

1. A method of drawing a thick line, comprising:calculating a displacement D, wherein the displacement is a function of the line thickness W; using a line drawing algorithm to determine line drawing parameter values for a single offset line, wherein the offset line is parallel to an origin line and

1. A method of drawing a thick line, comprising:calculating a displacement D, wherein the displacement is a function of the line thickness W; using a line drawing algorithm to determine line drawing parameter values for a single offset line, wherein the offset line is parallel to an origin line and offset from the origin line in a minor axis direction by the displacement; for each major axis pixel coordinate of the offset line: selecting a boundary pixel having the major axis pixel coordinate and a first minor axis pixel coordinate determined using the line drawing algorithm; selecting a set of additional pixels adjacent to the boundary pixel, each having the major axis pixel coordinate, wherein the number of pixels in the set is a function of W; and setting each of the selected pixels for subsequent drawing. 2. The method of claim 1, wherein W is equal to the line thickness.3. The method of claim 2, wherein the displacement D=FLOOR((W?1)/2).4. The method of claim 1, wherein the line drawing algorithm comprises a midpoint line algorithm.5. The method of claim 1, wherein the step of selecting W?1 additional pixels is independent of the line drawing parameters associated with the line drawing algorithm.6. A computer system, comprising:a frame buffer comprised of an array of storage elements; a display comprised of an array of pixels corresponding to the array of storage elements in the frame buffer; a video controller adapted to produce an image on the display representative of the contents of the frame buffer; and a first graphics engine adapted to draw a thick line in the frame buffer by calculating line drawing parameter values for a single offset line and invoking a routine for each major axis pixel coordinate in the major axis range of the offset line where the routine draws a first pixel by invoking a line drawing algorithm and draws at least one additional pixel adjacent to the first pixel using a stepping routine; wherein the offset line is parallel to and displaced in the minor axis direction from a center line of the thick line. 7. The computer of claim 6, wherein the displacement of the offset line is a function of the thickness of the thick line.8. The computer of claim 6, wherein the displacement D=FLOOR((W?1)/2), wherein W is the thickness of the thick line.9. The computer of claim 6, wherein the line drawing algorithm is the midpoint line drawing algorithm.10. The computer of claim 6, wherein the subroutine draws W?1 additional pixels, wherein W is the thickness of the thick line.11. The computer of claim 6, further comprising at least one additional graphics engine in parallel with the first graphics engine, wherein the first graphics engine and the additional graphics engine each operate on a portion of the graphic primitive.12. A graphics adapter, comprising:means for invoking a line drawing algorithm once at a major axis pixel coordinate to determine a first minor axis pixel coordinate and for selecting a first pixel defined by the major and minor axis coordinates; and means for invoking a stepping routine to select at least one additional pixel adjacent to the first pixel, wherein each additional pixel shares a common major axis pixel coordinate with the first pixel, and wherein the first pixel and the at least one additional pixel comprise one of a plurality of segments of a thick line. 13. The adapter of claim 12, wherein the first minor axis pixel coordinate corresponds to an offset line, wherein the offset line is parallel to and displaced in the minor axis direction from a center line of the thick primitive, and wherein the displacement is a function of the thickness of the thick line.14. The adapter of claim 13, wherein the displacement D=FLOOR((W?1)/2), wherein W corresponds to the thickness of the thick line.15. The adapter of claim 14 further comprising means for determining line drawing parameter values associated with the offset line.16. The adapter of claim 12, wherein the line drawing algorithm comprises a midpoint line algorithm.17. The adapter of claim 16, wherein the stepping routine selects W?1 additional pixels adjacent to the first pixel, wherein W corresponds to the thickness of the thick line.