Make a pyramid with triangular base and circular cross-cut top?

Hello, I am using the 3D printing template.

I am trying to make a 3-D printable pyramid with a triangular base and a circular cross cut near the top. I made a quick sketch in paint (haha) if you are not following what I need.

The tricky part is that I want the 3 lines that connect the triangular base to the circular top to go from sharp edges gradually rounding into the circle. Basically the large triangle morphs into a smaller circle as you go up from the base.

Can this be modeled in sketchup?

There are many ways to do this depending on the result you want.
One of the most basic is to use the move tool with the alt key to autofold he surface.
Is this the shape you are after?

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Yes this is exactly what I want, however did you notice the edges from the base to the top as you rotated it at the end? It is as if the edge is somewhat softened going up but never disappears completely into the circle. Can these edges be made smoother?

Thanks so much!

What do you want? a curved top, smooth edges, rounded corner, all of these are possible but what do you want?
Try having a go yourself then show is the model and the bit’s that aren’t right.

I’m not completely sure what you are troubled by, but here are a couple of thoughts. First, the dark lines along the edges are profiles. SketchUp draws these to show the virtual edge of a smoothed shape so that it doesn’t vanish into the background. You can change the weight of profiles or turn them off entirely in the style. Second, there are some shading effects where the curved parts change to the triangular flats on the sides. You can use the soften edges window to adjust this effect. Due to the shading technique SketchUp uses they will never go away completely, but you can tweak the appearance.

I think you have address my needs. Thanks

Since it is just a sketch to show an artist what I want painted, I think it will do. If I want it to be perfect I may soften the shading.

If you prefer, you can construct the object edge-by-edge and then exercise greater control over which edges get softened and which do not.


More like this? The image on the left was created with autofold … the one on the right with the Spirix plugin:

Autofold or hand stitch is the same geometry in this case.

Yes the spirinx one is very close to what I want. I bet if I tweaked it it would be perfect.

The one on the left is wrong because the triangles on the sides are all perfectly flat surfaces when I want them to be curved at the top and then slightly less curved as it goes down until it is completely straight at the bottom (forming the triangle.) If you look at my next post you will see some “phantom” triangle shading up the 3 sides of the pyramid. I want to minimize and round that off as much as possible, much like you would apply sandpaper to a wooden block of that shape until you have a very smooth edge as you go up. Once again, I think the spirinx plugin is exactly what I want.

Here is what I mean. now I am new to sketchup, so please point me to the link where I get the plugin and instructions to install Spirinx.

And the next problem that I have is getting 3D text to run down the spines perfectly. Here is my mockup. I did get the “the” pretty close to perfect, but it was a happy accident. I cant get the other word to bind to the surface as perfectly centered and also flat on the spine.

You can see the phantom triangle shading. I can minimize that by playing with colors and textures, and that helps minimize the LOOK of it, but the shape is actually slightly wrong as I explained int he last post. The triangles on the side shouldn’t be flat but have some gradient curvature, as i tried to explain above.

You can find the plugin at

In order to create the shape you want, you will need to create two templates … one for the triangle and one for the circle. If the circle is made up of 24 segments, then each of the edges of the triangle should be 8 segments (1/3 of 24). The Spirix Create Group function will grab all un-grouped geometry in the model in the order they were created. To construct the first template, create the triangle and group it the normal way. Then trace around the triangle starting at the right-hand point and continuing counter-clockwise around the perimeter. After creating each edge, you need to divide it before moving on to creating the next line. When done, use the Spirix Create Group and give it a name:

For the circle, simply create a circle with 24 segments picking a radius point on the x-axis (this aligns the start and end of the circle with the start and end of the triangle). Use the Spirix Create Group to create a second group with a different name:

Noting that the center-to-apex distance of the triangle is (arbitrarily) about 48 inches, I used a height of 48 inches with the following Spirix parameters:

You can use the move, scale, rotate, and mirror tools to modify the templates … however, editing them inside the group will usually change the order of the edges and cause unexpected results.

[quote=“sebastian, post:11, topic:20559”]… You can see the phantom triangle shading. I can minimize that by playing with colors and textures, and that helps minimize the LOOK of it, but the shape is actually slightly wrong as I explained int he last post.
See screenshot on how to “avoid” that triangle shape in SketchUp’s geometry.
(all just with basic tools)

(viewed from a slightly different angle)

thanks everyone :heart_eyes: :cherries::sushi::beers::heartpulse::gift_heart::fireworks::fireworks::floppy_disk:

Hi Dan,

I know how to make a line, but not with segments.

I know how to make an arc but not with segments.

I don’t know how to connect the segments ebtween the line and arc.

I know how to rotate, but don’t know how to copy rotate.

Can you help me with these or point to a tutorial?

[quote=“sebastian, post:16, topic:20559”]
I know how to make a line, but not with segments.[/quote]
See @jimhami42’s post about ‘Divide’ in the right click context menu when clicking in an edge.
‘Divide’ also applies to a basic arc. Or when/while cteating an arc just type the number of segments plus s and hit enter and continue creating the arc. To get 11 segments type 11s [Enter]

Use the ‘Line’ tool to stitch them (edge segments and arc segments) together. Then apply the ‘Eraser’ tool while holding down [ Ctrl] on the stitch lines to hide and smooth them.

While using the ‘Move’ or the ‘Rotate’ tool hit [Ctrl] once to get the **+**sign at the cursor, meaning copy. So you’ll either move or rotate a copy of the selection you made.

If you vary the spacing of the points on the line and circle, you can achieve a softer corner. However, the corners of a triangle are very pointy (and possibly dangerous) and pretty much any solution is going to have a sharp edge near the extremes.

trircle.skp (1.9 MB)

pyramid.skp (16.6 KB) Is this it

pyramid.skp (16.6 KB)