Hi,
I want to a make a triangular prism, 1m tall and each of the three faces 500mm wide.
i’ve been trying by making a circle with three vertices but I can’t quite get it right. I want to be millimeter perfect.
Thanks for any help!
C
One way would be to enable the bundled plugin add mesh extra objects.
Add menu- mesh - math function - triangle - equilateral (scale 1 is 1m, you can not set scale to less)
in edit mode scale 0.5 (now each edge is 0.5)
select all and extrude Z 1m
Merge at center the top verts.
2 Likes
Hey, @Crumbs! I think you were on the right track with the 3-vertex circle idea, but you really need to know what dimensions to make that circle, and I think the number one dimension you need is the radius. This is where math comes in and my amateur proof below hopefully can help.
Here’s what I’m tracking:
- The triangle inscribed in a circle with 500 mm sides is an equilateral triangle.
- The angles of that equilateral triangle are all 60°.
- The distance from the center of the triangle to one of the points is equal to the radius of the circle.
- Dividing the equilateral triangle into three equal triangles gives you three smaller triangles that can be further divided into 30° 60° 90° right triangles.
- The lengths of the sides and hypotenuse of 30° 60° 90° right triangles follow the 1, 2, √3 ratio.
- By cross multiplying, we get that the length of the radius of the circumscribed circle is equal to approximately 288.675.
Here’s my proof:
Or we could just go to the equilateral triangle Wikipedia page and see that the radius of the circumscribed circle follows the formula R = a/√3:
Now, in Blender, just create a circle with three vertices and a radius of 500/√3. Hopefully this helps and let us know if you have any questions!
3 Likes
Lots of ways to skin this cat:
3 sided circle:
change the x dimension in the side panel to your desired .5 meters:
then copy the x scale value to the y scale value:
Then you can apply scale and extrude it up 1m
3 Likes
reminds me of the proportional dimensions thread 
But better for my uneducated brain than Hunkadoodle’s 
1 Like
You know, Blender lets you “skin the cat” in ways that appeal differently to different people. I suppose the beauty of asking a question like this on this forum is that it will often elicit diverse ways of doing the same thing with the same result, and it will be up to the asker to choose which works best for them in their situation.
It also challenges me - a Blender user myself - to think differently about how to work. Thanks everyone for your input and willingness to help!
1 Like
My 10 cents worth…
Divide wanted radius by present default diameter, then move the center point up 1m on z.
Do you have Edge Length turned on in the overlay dropdown ???
2 Likes
while we’re skinning cats, here’s another way:
start with a plane:
in edit mode select all and merge to center to make a single vert at the origin:
extrude that point .5 meters along the x axis:
set your origin to the 3d cursor, then extrude that point, while in the extrude mode, press R to rotate that point, press z to rotate on the z axis, and type 60 to rotate it into position:
now select all points, and press f to fill that triangle
then select all and extrude up 1 meter:
4 Likes
Create an equilateral triangle with Spin tool ( step = 1, angle = 60°) and scale it to the desired size. Select it and extrude one meter. Done.
Thank you for everyone’s suggestions. I’ll get to try these techniques out and report back how I get on.
Amazing, thanks again!
Oddly, this is not giving me an equilateral. Should that be a an option available to choose from the Add menu?
Applying the x scale to the y scale worked particularly well, thanks!
1 Like
