When creating a sketch, it is sometimes easier to define certain relations between sketch entities – instead (or in addition to) setting the entities dimensions. Moreover, a “good” sketch should be “completely defined” – otherwise sketch alteration can lead to unexpected and unpleasant results. In this article we deal with line and line-to-line relations.
Look at the sketch above. You can see 4 lines, which already have certain relations (some of them can “appear” during line creation). 2 lines are parallel to each other, 1 line is horizontal. Suppose, we want to turn this quadrangle into a right-angle trapeze – what relations should we add?Well, first of all, let’s make the upper and lower bases parallel. Since the upper base is already a horizontal line, let’s do the same with the lower base:
Select the lower line (Click on it) – you will see line properties window on the left of your screen. Choose “horizontal” relation.
Now, let’s make one of the side lines vertical (remember, we want a right-angle trapeze).Click on the left line, and choose “vertical”… Ooops, the second line became vertical as well – that’s because the lines are defined as parallel!
We need to delete this relationship. It can be done by one of the 3 ways:
- The easiest one is clicking on the parallel icon and pressing delete.
- However, since we are already “inside” line’s properties, we can edit the existing relations in the window on screen-left.
- The third way – is to view ALL the relations of the sketch, by pressing the “Display/Delete Relations” button in the sketch menu.
Use either way to delete the parallel relation between the lines. No, set the dimensions of you trapeze – click on each line to define its length. You can also define the angle between 2 lines – just click on 2 lines when inside the “dimensioning” feature. Your trapeze is ready!
Editing and more
If you want to turn the trapeze into a parallelogram – you will have to delete the vertical relation of the left line (just select it and press delete), and set a new relation between the side lines.
To do that – select 2 lines (by pressing and holding CTRL you can select multiple entities). Once you do that – you will automatically see the “add relations” window on the left. Press “Parallel” – and your trapeze will turn into parallelogram!
But that’s not all! – in the next article, we will discuss the line-point and line-arc relations.