I want to make a polygon of with x # of sides…

I DON’T want all the sides to be the same length (it will not be regular)…

Any ideas for how to do this (are there constraints I can use)?

UPDATE:

In fusion 360 I believe this can be done by constraining the vertices to be “coincident” and simply modifying side lengths.

I don’t know the angles…

Thanks!

# How do I make an irregular polygon in SU?

What information do you have? You know the number of sides presumably. Do you know the length of each side, and the angles?

Draw a large rectangle.

Use that as a basis for your smaller irregular polygon’s edges.

If it’s to vary only slightly from a regular polygon you could draw one of those, then select it, right-click > context-menu > Explode, to make the perimeter into separate edges.

Then you can change selected edges - e.g. by using the Rotate or Move tool, or draw a new edge and erase the unwanted parts…

If it’s really different draw one base edge, then use the Guide tools to adds temporary construction lines, which can be rotated into new alignments etc, or the Protractor tool to set a guide at a given angle from an existing edge…

As @endlessfix says you need to know at least a few things like angles and some side lengths to at least get you started…

Hello,

I only have the lengths of the sides, and the order the need to go in…

I was hoping to start with regular polygon , then change the length of 2 of the sides (that happen to be different).

Thanks!

How many sides and what are the dimensions?

Hmmmmm… I’m thinking through my basic geometry here and I don’t think it’s possible with only the side lengths. That is, without angle information there are infinite ways to make a polygon with sides of a given lengths. You could draw the sides separately to the right length as lines with the line tool, and then use the move tool and rotate tool to assemble them. But without knowing the angles the polygon could be many different shapes even with the right length sides.

Agree. I think a triangle is the only polygon that can be completely specified using just the lengths of the sides.

Thanks!

I was hoping to use contraints so that vertices are forced to be coincident…

Will update my post now…

For example:

Start with 5 pieces of spaghetti that must be connected in a specific order, defined by points

A B C D E F

All lines segments are congruent except for BC and EF with are 1/2 the lengths of AB, CD etc…

Point F is coincident with point A (bc this is where the polygon closes).

Thanks!

Ok so this might be possible if the starting node points are defined by a regular polygon and not more than two adjacent sides are adjusted in length. That way each adjusted side remains anchored to a define node on at least one side. I would proceed as @TIG suggested and begin with a regular polygon, maybe placed on the surface of a larger face to help keep your new lines coplaner. Then draw the new lines with the line tool and use rotate to join. You can explode the old polygon to erase the unneeded sides.

Thanks!

Will look into this will look into this…

I agree as well. Consider a square - a four-sided polygon with equal length edges joined at 90 degree intersections. Now skew the square sideways or up-own and you have a different shape (the general case of a rhombus, of which a square is a special case). Or consider a polygon with many sides, joined with imaginary hinges (e.g., a necklace made of short stiff segments). Lay such a collection of connected sides on a table, and you can distort the shape into infinite forms, convex, concave, a mix, etc.

Side lengths are insufficient to fully constrain the shape of a polygon with more than three sides, as @slbaumgartner noted.

Thank you to everyone who chimed in on this topic.

It seems as SketchUp is not capable of parametrically simulating movable joints as Fusion is, but it was great to hear from everyone along the way…

I cut these on our CNC, if anyone would like to see a loose “proof” of the concepts I was curious about…

Thanks again!