FIGURE 1.22 Horizontal and parallel relations are added.
The colors represent sketch states. It may be impossible to see this in the black and white printing of this book, but if you are following along on your own computer, you can now see one black line and three blue lines. Sketch states include Underdefined, Overdefined, Fully Defined, Unsolvable, Zero Length, and Dangling.
n Blue: Underdefined. The sketch entity is not completely defined. You can drag a portion of it to change size, position, or orientation.
n Red: Overdefined. This can mean a number of things, but it is usually caused by con- flicting relations or dimensions. For example, if a line has both horizontal and vertical relations, it becomes overdefined because one of the relations is satisfied, while the other is not.
n Black: Fully Defined. The sketch entity is fully defined by a combination of sketch rela- tions and dimensions. A sketch cannot be fully defined without being connected in some way to something external to the sketch, such as the part origin or an edge. Multiple external entities may be used, as appropriate. (The exception to this rule is the use of the Fix constraint, which, although effective, is not a recommended practice.)
n Pink: Unsolvable. The difference between pink and red is that red conflicts with another relation but is in a potentially correct location, whereas pink conflicts with another rela- tion, but is not able to move to a correct location, generally because of another red entity.
n Yellow: Zero Length. Solving the sketch relations would result in a zero-length entity; for example, this can occur where an arc is tangent to a line, and the centerpoint of the arc is also coincident to the line.
n Brown: Dangling. The relation has lost track of the entity to which it was connected.
There can be entities with different states within a single sketch. Also, endpoints of lines can have a different state than the rest of the sketched entity. For example, a line that is sketched horizontally from the origin has a coincident at one endpoint to the origin, and the line itself is horizontal. As a result, the line and first endpoint are black, but the other endpoint is underdefined because the length of the line is not defined. Sketch states are indicated in the lower-right corner of the graph- ics window and also in the status bar. You can see that dragging one corner allows only the lines to move in certain ways, as shown in Figure 1.23.