Using the Loft feature to create irregular pyramids on a cylindrical surface

[valentin.finozzi]

Hi,

I'm trying to recreate this following object:

What I'm doing is a simple revolution as the base, I create an offset vertical plane, draw an irregular polygon and a point on it, project this polygon onto the cylindrical face as a 3D sketch and then use Loft from the projected polygon to the point on the offset plane.

I've had mixed results. While I've been able to create some pyramids I am getting the most varied of errors while using Loft, "not a closed loop", "creating non manifold geometry", "the attempted operation did not produce a meaningful result" or simply "could not build this Loft".

Is there a better way of going about this?

Thanks in advance!

[cadman777]

if Walt's part looks like it'll work, then maybe you can modify your base cylinder (cut the top at an angle or with a spline) and then make the changes he made. Then add another smooth/unmodified cylinder to the top of it. The modified cylinder may have to be a bit larger so the smooth cylinder will fit and look proper.

[johnsonshiue]

Hi! Here is another example using Bend Part. Basically, you may start with a box. The height is equal to the vase height. The length is equal to the diameter*PI. On the planar face, it is relatively easy to create random point Loft features and use Sketch Driven Pattern to populate it. Lastly, use Bend Part feature to roll around 359.99 deg. Attached is a 2-minute attempt in 2023.

Many thanks!

[cadman777]

Thinking outside the box again, I see.

Very nice!

[arron.craig]

I think you will get something pretty close with the freeform tool. I had a quick play around with it (see attached recording). 

The downside is that you won't have more than 4 sides to each feature. 

https://autode.sk/3gN31Fr

[cadman777]

Nice!

One thing I always wondered about is what the difference is between Sculpt and Stitch when you join surfaces?

[SBix26]

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@cadman777 wrote:

One thing I always wondered about is what the difference is between Sculpt and Stitch when you join surfaces?

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In this case, there wouldn't be any difference.  However, Stitch requires that each surface shares edges with the adjacent surfaces, whereas Sculpt can create a solid from merely intersecting surfaces and workplanes.  Sculpt requires that the volume be completely enclosed, but the surfaces don't need to be trimmed beforehand.  Quite a bit more flexible than Stitch.

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Sam B

Inventor Pro 2023.2 | Windows 10 Home 21H2

[johnsonshiue]

Hi Chris,

Adding to Sam's comments, Stitch is literally as the word implies. It is like a sawing operation. Each surface body is connected within predefined tolerance. The result can be a bigger piece of surface body (with multiple faces). Or, it can be a solid body.

Sculpt is more like making compartments. The selected tools separate a solid body into multiple cells. Depending on the user-defined direction, the cells are joined or cut from the target body.

Many thanks!

[cadman777]

Thanx Sam, that's exactly what I wanted to know.

I always use Stitch to join surfaces.

So what would be the comparative benefits of using Sculpt for that over Stitch?

I always make sure the edges of the surfaces being joined are always coincident.

[cadman777]

Thanx for the added info Johnson.

I never even thought of using Sculpt to join surfaces.

So what would be the benefits either way?

If either of you guys can direct me to a concise and well-written comparative explanation with examples that illustrate the purposes, you won't have to spend time educating me. 😜

[johnsonshiue]

Hi Chris,

I don't have any public appropriate documentation to share. All I can offer is my understanding how things work. The two commands are based on two completely different types of operations. The Stitch command processes the geometry on a per face basis. The Sculpt command handles watertight cells (compartments). In some way, the end result can be the same, when the distinct faces form a watertight volume. However, that is the only case.

The Sculpt, to certain degree, is more flexible in terms of inputs (workplanes, surfaces, and faces). But, to get a meaningful solution, the inputs have to form a volume.

Many thanks!

[cadman777]

Thanx Johnson for the elaboration.

I think it's making sense now.

I'll 'sleep on it' and think more about it in the morning and do some testing.

Cheers...

[jknudsenXPMU6]

How about just making a regular pyramid/shape who's base is inside your cylinder? I.E. don't try to loft to the cylindrical surface. Make a pyramid that crosses through then combine them.