Draw a triangle given 3 sides


#1

I ran into a problem with SketchUp.
I have measurements for a site with everything triangulated to accurately locate it.
Here is the problem. I start with the dimension of 3 sides of a triangle and then try to draw the triangle (and ultimately to add a lot of others to it). Just as an example I have drawn here a 3:4:5 right triangle with sides: 3’, 4’, 5’. In this case I drew the 3’ side vertically which gives me 2 vertices of the triangle. To locate the other vertex I draw a 4’ circle from one vertex (the end of the 4’ side will be on this circle) and a 5’ circle from the other vertex. Where these circles intersect it the 3rd vertex of the triangle. (Please ignore the fact that because this is a 3:4:5 right triangle we know that the other side will be at right angles so we don’t need to locate the vertex with the 2 circles. We want this to work for all triangles where in general we don’t know the angle).
The result is shown below. The 5’ side is 4’ 11 15/16”. Also the angle is not 90 degrees. This is because SketchUp doesn’t draw actual circles (you can see the segments in the drawing). The differences are small and the accuracy can be increased by increasing the number of segments in the circle. (Accuracy decreases with increasing radius.) However, the inaccuracy is still annoying and it becomes more noticeable as you connect many triangles.

I’m wondering if anyone knows of a solution to this in Sketchup?


#2

Sketchup’s circles/arcs are ‘segmented’ - NOT a continuous ‘curve’.
This means that the intersection of two Sketchup circles’ ‘edges’ is likely to not fall on either circle’s circumference.
In fact, unless the intersection is by a lucky coincidence a ‘node’ on the arcs’ segments it will never be !
Try my tools to find ‘true-intersections’ etc…
The guide-points/lines generated help you find the true points you desire…
http://sketchucation.com/pluginstore?pln=TrueTangents


#3

Trilateration … SketchUp plugin by Didier Bur (Recent update by TIG)
Command to draw a triangle, knowing its 3 sides lengths (trilateration)


#4

Thank you very much.
That worked perfectly.

Is there q quick way to get rid of the guidelines and guide points after using them?
Since I am creating large numbers of triangles, all tied together, that could end up being a big job.

Huck


#5

The trilateration plugin took care of removing the guide points.


#6