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Examples

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

Example 1:

We are given segments s_1, s_2, and e, and we want to add the dashed vertical extensions through p and q.
  • set . and / snapping on, go into line mode, and reset axis system with M-`.
  • go near p, press C-` to set origin and to turn on directional snap.
  • go near p', click left, and extend segment to s_2.
  • go near q, press ` 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 . and < snapping on, go into line mode, reset axis system, set snap angle to 90 degrees.
  • go near p, press C-` to set origin and directional 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 C-` to reset origin and to turn on directional snapping. Now both directional snapping modes are on, the snap lines intersect in z.
  • click left at z, goto x and press `, 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 autodir snapping to get it horizontal.
  • place p with boundary snapping, draw the rectilinear curve up to r with autodir snapping in 90 degrees mode.
  • now go to p and press C-`. The snap lines intersect in q. Click there, turn off directional snapping with M-`, 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 `
  • go to q and press >. This puts the base direction from p to q.
  • set directional snapping with - 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 system with M-`.
  • with autodir snapping, draw a horizontal segment pq.
  • go to p, place origin and turn on directional snapping with C-`.
  • duplicate segment with d, go to q and pick up q for rotation (with Ctrl and the middle mouse button). Rotate until segment falls on the next snap line.
  • turn off directional snapping with -. 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 directional snapping on again. Duplicate sector, and rotate by 60 degrees using directional 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 autodir 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 autodir 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 autodir snapping mode ensures the position with respect to q. We will use directional snapping from p to get it right: Go near p and turn on vertex snapping. Press C-` to place the origin at p and to turn on directional snapping. Now it is trivial to place r.

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