5.6 Examples

It takes some time and practice to feel fully at ease with the different snapping modes, especially angular snapping. Here are some examples showing what can be done with angular snapping.

Example 1:

We are given segments s₁, s₂, and e, and we want to add the dashed vertical extensions through p and q.

• set F4 and F5 snapping on, go into line mode, and reset axis orientation with Ctrl+F2,
• go near p, press F1 and F8 to set origin and to turn on angular snap.
• go near p', click left, and extend segment to s₁.
• go near q, press F1 to reset origin, and draw second extension in the same way.

Example 2:

We are given the polygon C, and we want to draw the bracket b, indicating its vertical extension.

• set F4 and F9 snapping on, go into line mode, reset axis orientation with Ctrl+F2, set snap angle to 90 degrees.
• go near p, press F1 and F8 to set origin and angular snapping
• go to x, click left, extend segment to y, click left
• now we want to have z on a horizontal line through q: go near q, and press F1 and F8 to reset origin and to turn on angular snapping. Now both angular snapping modes are on, the snap lines intersect in z.
• click left at z, goto x and press F1, goto t and finish bracket.

Example 3:

We want to draw the following "skyline". The only problem is to get q horizontally aligned with p.

• draw the baseline using automatic angular snapping to get it horizontal.
• place p with boundary snapping, draw the rectilinear curve up to r with automatic angular snapping in 90 degrees mode.
• now go to p and press F1 and F8. The snap lines intersect in q. Click there, turn off angular snapping with Shift-F2, and finish curve. The last point is placed with boundary snapping.

Example 4:

We want to draw a line through p, tangent to C in q.

• with vertex snapping on, put origin at p with F1
• go to q and press F2. This puts the base direction from p to q.
• set angular snapping with F8 and draw line.

Example 5:

We want to draw the following "windmill". The angle of the sector and between sectors should be 30 degrees.

• set vertex snapping, snap angle to 30 degrees, reset axis orientation with Ctrl+F2,
• with automatic angular snapping, draw a horizontal segment pq.
• go to p, place origin and turn on angular snapping with F1 and F8,
• duplicate segment with d, go to q and pick up q for rotation (with Alt and the right mouse button, or by switching to rotate mode). Rotate until segment falls on the next snap line.
• turn off angular snapping with F8. Choose arc mode, variant "center & two points".
• go to p, click for center. Go to q, click for first endpoint of arc, and at r for the second endpoint. Select all, and group.
• turn angular snapping on again. Duplicate sector, and rotate by 60 degrees using angular snapping.
• duplicate and rotate four more times.

Example 6:

We want to draw a c-oriented polygon, where the angles between successive segments are multiples of 30 degrees. The automatic angular snapping mode makes this pretty easy, but there is a little catch: How do we place the ultimate vertex such that it is at the same time properly aligned to the penultimate and to the very first vertex?

• set snap angle to 30 degrees, and turn on automatic angular snapping.
• click first vertex p and draw the polygon up to the penultimate vertex q.
• it remains to place r such that it is in a legal position both with respect to q and p. The automatic angular snapping mode ensures the position with respect to q. We will use angular snapping from p to get it right: Go near p and turn on vertex snapping. Press F1 to place the origin at p and F8 to turn on angular snapping. Now it is trivial to place r.