Geometrical Representation (Basics)

CAD6 drawings contain a sequence of objects and logical combinations of such.

"Objects" are entities that contain the data of a geometrical representation of a drawing element like a "line" or a "circle". The geometrical data consists of a number of point coordinates and some additional data. A "line" e.g. is made up of two point coordinates ("start-point" and "end-point") plus some additional data like line width, line color, layer number etc.

Representation of a line

All point coordinates are defined in a Cartesian coordinate system (called "Workspace") which has a valid coordinate range of MKI_COORD_MIN (-1e12 mm) to MKI_COORD_MAX (1e12 mm). Its axes increment to the right and upward. The coordinates are always stored in physical millimeters, i.e. they determine the printed size of the object. A square having a physical side length of 10 mm will always be printed, plotted or exported with a side length of these 10 mm (exception: explicit scaling of the print-out or scaled mappings from Model Space to Paper Space). If the user creates a square with a logical side length of 2 meters using a scale of 1:100, the square will have a physical side length of 20 mm, as it will be printed with that side length of 20 mm.

Coordinate orientation

Each point in the coordinate system is determined by a X- and Y-coordinate, e.g. (0.0,1.0). The valid physical coordinate area is MKI_COORD_MIN (-1e12 mm) to MKI_COORD_MAX (1e12 mm). All definition points of the objects have to lie completely inside this area. No coordinate may ever have the value 1e300 mm, as this value is defined as "invalid / undefined value" and may cause undefined behavior.

Angles are always stored in radiant [rad]. Typical values are -pi up to pi, values from -2pi up to 4pi are allowed.

Representation of angles

Within this workspace, the user can place several pages. At least one page must exist at any time, giving the user an orientation. The maximum page size is 25 × 25 meters or approx. 27 × 27 yards.