When the face of your monitor is the X-Y plane, the Z-axis is pointing toward you (see Figure 4.2).Ĥ.4 2D CAD Drawing.
Most CAD systems use the right-hand rule for coordinate systems if you point the thumb of your right hand in the positive direction for the X-axis and your index finger in the positive direction for the Y-axis, your remaining fingers will curl in the positive direction for the Z-axis (shown in Figure 4.1). No matter what CAD software system you will be using, it is helpful to understand some basic similarities of coordinate systems. Coordinates for 3D CAD ModelingĢD and 3D CAD drawing entities are stored in relationship to a Cartesian coordinate system. However, CAD drawings are accurate only if the drawing geometry is defined accurately when the drawing is created.
#AUTOCAD MAC DRAW LINE BETWEEN TWO LINES MANUAL#
Wow! That’s a lot better than the 1 in 40 accuracy of a manual drawing. If you drew two beams, each three times the distance from the Sun to Pluto, and made one of the beams just 1 mm longer than the other one, a CAD system could still accurately represent the difference between the two beams. This produces a theoretical accuracy of around 1 in 10 quadrillion (10 16). The internal precision of drawings created using CAD systems is limited by the 64 bits (base-2 places) typically used to represent decimal numbers in a CAD system. For example, a hand-drawn survey created at 1″ = 400′ might be accurate to a range of plus or minus 10′.
Good manual drawing technique can typically produce a drawing accurate to about 1/40th of the drawing scale. Lines drawn using a CAD system are highly accurate definitions-much greater than you can see on a computer monitor. Reviewing the basic geometry of these elements helps you define and combine these elements in your drawings and CAD models.Īccurate construction is critical to creating useful drawings.
2D drawings are composed of simple entities such as points, lines, arcs, and circles, as well as more complex entities such as ellipses and curves. Engineering drawings combine basic geometric shapes and relationships to define complex objects.
0 kommentar(er)
