I need to join two walls of 8m and 5m length at a distance of 10m.
It boils down to creating a triangle from three edges with lengths 10, 8 and 5 meters.
Normally you would to this by intersecting two circles (radius 8m and 5m resp.) with the centers at 10m distance.
But Sketchup seems not to have “snap on Arc”when drawing an arc.
Is there a way to create the triangle in a precise way in Sketchup?
You could use a trilateration extension to locate the corners of the triangle. I know of two, both available at SketchUcation:
My own SB Trilateration, or Didier Bur’s version.
Thanks Steve!
I will try the plugin and update.
I hoped that there is a key I can press in Sketchup to snap on the arc and not a segment.
I tried SB Triangulation for 2D and 3D.
In 3D it works.
But in 2D it does not:
I draw a face and on the face an edge 10m long.
Then I activate the 2D trilateration tool and select the face, the first center (being one end of the edge), enter the first radius and then select the second center (the other end of the edge).
When I enter the second radius and press enter, nothing happens. When I re-enter the second radius, a message pops up to first select a center.
Do you know where it is going wrong?
I then saw that you have another plugin called “Circle intersect”. This one works in 2D. (it requires however to have two arcs drawn beforehand in order the guides for the triangle to be drawn)
If you are mathematically inclined you could use the cosine rule to find the included angle between two of the sides - or use an online calculator to give you it. You can then lay those down using the protractor tool and then connect the 2 ends to give the third side.
I’ll look into it later when I get a chance. Last I checked it was working properly.
My circle intersect uses most of the same math internally but was built for situations where you already have arcs or circles in the model and want to know the points where they intersect.
Edit: The extension still works for me (see attached video. You can’t see me entering side lengths, but that’s what happens in the dead spots of the video. Also, due to a Mac oddity, the cursor changes back to an arrow when it shouldn’t have). If that’s not what you are getting, please run it with the Ruby Console window open and tell me what (if anything) shows there.
I wonder if this is a question of misunderstanding of what it does. It finds the vertices of potential triangles based on your input values and marks them with two guide points and a guide line joining them. If you want a triangle, you need to draw its sides yourself using the ends of the baseline and one of the guide points. I did it that way for two reasons. First, there are always two possible triangles (or none) and it isn’t clear which one you actually wanted. Second, this way you can use it with distance measurements to plot where something on a site is without cluttering the model with spurious triangles.
Thanks, I agree, I could calculate the angle.
Depending on the values, I can however get rounding errors and then the lengths are not precise anymore in Sketchup (when switching the display precision to 8 digits).
Using 54.4105, the length is off on the 4th digit after the decimal point.
I try to avoid calculating, if there is another way in Sketchup to get precise geometry.
Thanks. I will try again tomorrow with the console open.
The solution with drawing guide points makes sense to me. I normally will not draw triangles, but place walls or other objects along the sides of the virtual triangle. So no need to draw the edges. Getting guide lines instead of points could be useful in some cases.
If you look at my 2 SU screenshots you will notice in the first I’ve laid out 2 exact lengths of 5 and 10m with an angle calculated and drawn at ~52.4º. The second screenshot is connecting the 2 ends and you see the dimension is 8.000m to 3dp (7.999957m to 6dp). I’d like to see a bricklayer that can build 5m,8m and 10m walls to 4 decimal places,
See this SU file for ideas.
Triangle from 3 known sides.skp (170.6 KB)
OK, the bricklayer or woodworker will not work with a precision of 0.1mm, but a drawing in a computer program should be able to get it mathematically precise. It just does not look good to me, if a length in a model is shown as 7.9999 if 8 is meant.
Thanks. I also do not get closer than in your example. Pitty, it is not possible with SU internal tools to get it precise.
This seems the same idea as @Box has. But in the model something is not right, when looking at the corner:
Using @Guido 's formula there is no reason not to be accurate to 6 decimal places.
For 2D-Trilateration:
The ruby console shows he following, after I enter 8 and pressed enter for the second radius. No Guide points are drawn.
Yes, if you enter 52.41049704 or at least 52.410497 for the angle gamma.
I just used 52.4105 and got this.
I see, you have the model units on meters. I work with cm, so I get 800.000026cm using 52.4105.
Calculating the angle manually more precisely, we therefor can get it precisely to 8m within the 6d, even with model units set to mm.
