# How do I make following curve?

Hi, I’m trying to understand rhino better. I’ve basically trying to construct a piece of geometry given several constraints I can do it in fusion 360 no problem but rhino just breaks me. I’m given two lines parallel with set lengths. 43 and 25 units in my example. I want to connect these two lines with lines of two set lengths. 19 and 22 units how would I go about this?

As you can see my one dimension is above my top line How can I keep all of these lengths and the horizontal lines parallel to connect them into one curve. Attached a image from fusion 360 to display what I’m trying to create.

If these are 4 individual lines, simply enter `Join` while having them all selected, or alternatively click on the Join-button (jigsaw pieces). You’ll get what’s called a polyline, which is a collection of connected line segments.

Now, to remedy the issue with the overextended line segment, you can either select the relevant end point and simply snap it to where it should go. You should activate Point snapping, as well as the Gumball navigation tool.
Or you could simply delete the line, join the 3 other lines - like described above -, and enter `CloseCrv` or select the same command from “Curve > Curve Edit Tools > Close Curve”, which will draw the now missing segment for you between the start and end points of the joined, three other lines.

Try following frasshopper file to generate trapezoid if you know 4 sides. It is based on analytical solution, just use the sliders to determine the sides.
Side “a” is at bottom (25u), side “b” (19u) on the left, side “c” (43u) above and side “d” (22u) on the right.
The variables x and y are computed extensions of side “a”, the “h” is height of trapezoid
trapezoid.gh (11.8 KB)

And for fun a solution using Kangaroo2 (probably could be done better)

trapezium.gh (16.5 KB)

Hello - the proposed solutions are all very convoluted - the upshot is, Rhino does not have the constraints and parametrics that you expect from Fusion or any parametric modeler. GH does of course, but the approach is rather different.

-Pascal

Given that Rhino is not parametric, you will need some construction geometry. I was able to create this with the following steps.

-Draw 43 horizontal line from origin
-Draw R19 Circle on the left and R22 right.
-Draw horizontal line 25 length on the bottom quad of the R22 circle.
-Move R22 circle from right side of L25 line to left side of L25 line.
-Move L25 line to the intersection of the two circles
-Draw lines between end points.

File with steps included.
Polyline_Steps.3dm (109.8 KB)

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@Mark_Landsaat - nice solution.

… it is mainly a parallelogram that is sheared…
(screenshot of Mark s File + some additional graphics)

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I’m assuming there’s no way to move the horizontal 25 line to touch two circles. Like the imaginary Align two points > Maintain ortho orientation > Scale:no option

you can use object snap
http://docs.mcneel.com/rhino/7/help/en-us/index.htm#user_interface/object_snaps.htm

(wow copy paste from the help to the forum works to embed external image…)

@Mark_Landsaat , that’s a great solution.

For other folks, this book covers applied geometry in a way that typical schooling didn’t. It’s chock full of how to draw lots of things using just a compass and a straight edge (not even a ruler!)

Ruler and Compass: Practical Geometric Constructions - Kindle edition by Sutton, Andrew. Arts & Photography Kindle eBooks @ Amazon.com.

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@Mark_Landsaat

Thanks so much! I’ve gotten so lazy with parametric + constraints I was struggling to figure out how to create the construction geometry!

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