topic Re: Lofting is incorrectly twisting my Model in AutoCAD Forum

Lofting is incorrectly twisting my Model

noel — Mon, 27 Nov 2023 00:35:09 GMT

Hello everyone, i have a little experience 3D modeling in CAD and im having problems with my lofting/model.

Im trying to model an existing tank from Cloudworks, my work process would include

1. slicing the tank into vertical sections

2. drafting each cut profile, manually adjusting the linework to match existing tank

3. loft each section individually

4. union each section together, until it was 1 solid object

my problem is when i Loft (shown below) my model has twisting(?) in it , even with trying all the various loft options

some additional notes:

-Ive never had to model an existing structure precisely, so maybe this isnt the best work-process

-The scan data isnt clean, some sections of the tank is unable to be seen, so my model has vertexes and sections placed where i had the most data

-Made sure that the number of vertexes in each section is the same

-Because its an existing structure , arcs in the profiles are manually adjusted, thus they dont align perfectly, so some sections will be behind and some sections will be in front of the previous profile. I suspect this is the problem but im really not sure how to proceed

ive attached my drawing with both the model and linework

Any advice on my model or even approach to the project would be greatly appreciated , thanks

Re: Lofting is incorrectly twisting my Model

Valentin_CAD — Mon, 27 Nov 2023 09:27:20 GMT

@noel ,

Just explode the top layer and copy to the same elevation as the others before using LOFT - see attached drawing.

(Note: These object is not a circle or a ellipse)

Re: Lofting is incorrectly twisting my Model

noel — Mon, 27 Nov 2023 16:35:40 GMT

unfortunately i need to show the specific existing dimensions at certain intervals, so having my model be uniform throughout is not ideal. Thats why i approached this using a loft method, instead of just using an extrude function at the base.

I just dont understand how to fix the twisting when lofting between two objects that arent uniformly the same

Re: Lofting is incorrectly twisting my Model

Patchy — Mon, 27 Nov 2023 17:33:12 GMT

What has to be done to eliminate the squeeze is to draw a bunch of vertical lines using endpoint snap and then use LOFT with guides (the vertical lines)

Re: Lofting is incorrectly twisting my Model

noel — Mon, 27 Nov 2023 18:05:50 GMT

This is it, thank you

while i have extruded along a path using guide lines, Ive never lofted with guide lines, whats the command or process to do so?

Re: Lofting is incorrectly twisting my Model

Patchy — Mon, 27 Nov 2023 18:08:32 GMT

Loft, select all the polylines (5) then you should see the prompt for guides

Re: Lofting is incorrectly twisting my Model

noel — Mon, 27 Nov 2023 18:56:37 GMT

I think im misunderstanding something, apologies (i want to nail this for future reference)

lofting the vertical lines gets me to this, but when selecting the "guide" and then selecting my horizontal lines gets me an error

Edit: i understood my problems as i was lofting the incorrect profiles, thank you very much Patchy for the help!

Re: Lofting is incorrectly twisting my Model

Patchy — Mon, 27 Nov 2023 19:00:13 GMT

The reason they don't like to loft is because the polylines are overlapping.

I explode all them, used OVERKILL and then PEDIT to join them back.

then draw the vertical guides then they all lofted fine.