topic Re: Parametric 3d modeling in AutoCAD Forum

Parametric 3d modeling

jmrodriguesTT6UL — Wed, 19 Apr 2023 11:25:06 GMT

Hi, i would like to know if this is possible to do with Autocad or any other software that exports layered dwg.

For structure analysis, i need a parametric model like the attachment, to be able to type the values manually and the model adjusts the green rectangles size to be able to define wind load areas. There's several combinations and it takes too much time to draw manually. A parametric model with layers, would help me improve greatly the time spent defining those areas.

Is it possible to have a 3d parametric model like this one? The layers are needed to hide the areas for every wind direction and internal pressure.

Re: Parametric 3d modeling

pendean — Wed, 19 Apr 2023 12:40:10 GMT

Greetings @jmrodriguesTT6UL

Can we assume you do not have AutoCAD currently and therefore could not look this up in HELP, then explore this page for an introduction (your DWG file lacks all those pre-requisite settings)
https://help.autodesk.com/view/ACD/2023/ENU/?guid=GUID-899E008D-B422-4DF2-AC8D-1A4F5701ED4E

A quick websearch offers tips on how to get started with your DWG file
https://www.dlt.com/blog/2015/05/13/autocad-parametric-modeling
https://www.google.com/search?q=autocad+and+parametric+tips
https://www.autodesk.com/autodesk-university/class/Practical-Guide-Parametric-Drawing-AutoCAD-2016

It might help if you explored using a variant of AutoCAD that actually does structural elements (if that is your line of work) so you don't have to draw Plines if you need that, most variants are free to AutoCAD paid subscribers all day long like AutoCAD Advanced Steel https://www.autodesk.com/products/advance-steel/overview?term=1-YEAR&tab=subscription#:~:text=What%20is%20Advance,design%20to%20fabrication

HTH

Re: Parametric 3d modeling

jmrodriguesTT6UL — Wed, 19 Apr 2023 13:35:39 GMT

Hi, thanks for the reply, but that's exactly my question, if Autocad 3d can do this with parametric constraints.

I'm looking for defining L, C, H1, etc using input variables, and the model adjusts. Is it possible? Either by using blocks?

As for steel workshop drawings, we currently use Tekla Structures. This is for importing reference lines (not necessarily polylines) on structural analysis model, and an editable model would improve a lot our efficiency.

Re: Parametric 3d modeling

leeminardi — Wed, 19 Apr 2023 14:21:41 GMT

@jmrodriguesTT6UL wrote:

Is it possible to have a 3d parametric model like this one?

Yes and no! AutoCAD parametric features are limited to work in 2D planes. Since all of your geometry lies parallel to one of the 3 principal planes (XY, YZ, or ZX) you could construct 3D model that consists of complete 2D views of the geometry for each of the principal planes and use the constraints of the parametric systems.

For example, the plan view would be a rectangle on the XY plane (top view) and dimension L could be parametrically dimensioned. A complete end view of the structure could be create on the ZX plane (front view) with the UCS set to View. It would also need to include the edge that was included in the plan view as a parametric linear constraint can only reference geometry created in a plane parallel to that plane. Dimension L would be included in this plane too. Changing the value of L would require editing the 2 dimensions.

It would take some clever layer management and would be clumsy to implement.

Alternatively, you could just work with multiple 2D views in the XY plane but for the best approach use a 3D modeler that supports full 3D parametric modeling such a Inventor.

Re: Parametric 3d modeling

jmrodriguesTT6UL — Wed, 19 Apr 2023 16:34:33 GMT

Thank you for the reply.

I'm not an Autocad user, but we are considering purchasing a viable alternative. Using Inventor or Solidworks we are aware that works, but are expensive solutions just for drawing lines.

If Autocad does the trick, it would be preferable. Are there any native dwg alternatives that does the trick in 3D? The use of layers is important, to filter out the massive amount of lines these areas represent.

Using a Xref for different views would enable to "join" the model? The problem would be that the variables are the same for different views.

Re: Parametric 3d modeling

leeminardi — Wed, 19 Apr 2023 22:16:04 GMT

Is your intent that your structural analysis software will read a 3D AutoCAD .dwg or .dxf file and then you will be able to apply constraints and loads for a finite element analysis?

Is the topology of the structure always the same (i.e., the general beam layout) and all that changes is the dimensions? If so, a fairly simple AutoLSIP program could be used to create the 3D geometry but you would need to write expression for all the line endpoints as a function of the dimension variables.

Excel could also be used to generate line coordinates parametrically. For example, the following will create the end section. Just copy and paste the contents of cells I9 thru I13 into AutoCAD.

With the formulas displayed

Re: Parametric 3d modeling

pendean — Wed, 19 Apr 2023 23:12:40 GMT

@jmrodriguesTT6UL wrote:

...Using Inventor or Solidworks we are aware that works...

AutoCAD is older and has no such abilities as those two software packages: sorry, IMHO it will be a total waste of your time to try and jig-it to do anything comparable. Are you only shopping for price? Cheap tools take twice as much effort to do a task as the correct tool.

Have you explores Fusion360? Creo Parametric? Not sure they meet your need but worth experimenting with too.

Re: Parametric 3d modeling

jmrodriguesTT6UL — Wed, 19 Apr 2023 23:41:13 GMT

I don't know if most parametric modelers will do the trick, most are for solid modeling. I need those areas defined by lines that are dimension dependant separated by layers. Does inventor do this?

I like the excel idea, I didn't know it was possible. I'm just afraid of the rounding numbers, it could make lines not coincident with the angled ones, and that is an issue.

How do you create lines within a given layer with the LISP solution?

Re: Parametric 3d modeling

leeminardi — Thu, 20 Apr 2023 00:31:24 GMT

@jmrodriguesTT6UL wrote:
I like the excel idea, I didn't know it was possible. I'm just afraid of the rounding numbers, it could make lines not coincident with the angled ones, and that is an issue.
How do you create lines within a given layer with the LISP solution?

Don't worry about Excel rounding, as you can see under the AutoCAD command column there's 13 decimal digits (15 significant digits). As precise as AutoCAD. Some cells show a rounded number for clarity but there's more precision to these numbers.

A "layer" command can be included in the Excel output along with the line coordinates.

It sound like you have no Excel experience. Can someone in your company who knows Excel help you? You should also have someone with basic AutoCAD knowledge.

Re: Parametric 3d modeling

jmrodriguesTT6UL — Thu, 20 Apr 2023 07:17:15 GMT

Hi, i'm very comfortable with excel, what i have is no idea of the input commands for Autocad, didn't know it was possible to paste text with functions. I'll give it a go.

Thanks, you were very helpful. @leeminardi

Re: Parametric 3d modeling

jmrodriguesTT6UL — Thu, 20 Apr 2023 16:12:03 GMT

Working like a charm for the facade.

Thank you.

Re: Parametric 3d modeling

leeminardi — Thu, 20 Apr 2023 17:58:11 GMT

@jmrodriguesTT6UL I'm glad the Exel approach worked out for you.

Here's a modified version that let's you specify the layer. Getting the syntax to work with the straight layer command was frustrating so I used an AutoLISP format (command"-layer... .

The content of the cell H8 that creates the layer command is:

=CONCATENATE("(command ",CHAR(34),"-layer",CHAR(34)," ",CHAR(34), "s",CHAR(34)," ",CHAR(34), H8,CHAR(34)," ",CHAR(34),CHAR(34),")")

Since " (quote mark) means one thing in Excel and another in AutoCAD I use CHAR(34) (ASCII code for ") to create AutoCAD quotes in the concatenate command.

Just have a blank line of data when you want to declare a new layer (see attached). Of course, you could use an if statement that looks at the layer column to create a formula to fill down.

Please let me know if you have any questions.