Volume of 3d mesh?

Hello,

 

I'm using AutoCAD 2012 to project a hull of a ship I'm about to build. I'm designing it in 3d. I have red many tutorials, but I'm still not very good at 3d modeling, so I'm learning as I go.

I decided that for complex 3d shapes, working with meshes is best option. However, as I'm designing the before mentioned hull, I need to frequently check the volume of that hull to see if it passes under design limits.

However, I can't figure a way to do that. MEASUREGEOM command doesn't work with so complex shape, MASSPROP works only with 3d Solids, and I don't know any other commands.

I tried converting my mesh to 3d Solid, but got following error: "Mesh not converted because it is not closed or it self-intersects.

Object cannot be converted.".

After step-by-step redrawing I figured out that if two vertexes are on each other, AutoCAD cannot convert mesh to solid. However, I can't even merge two vertexes into one. Tools to work with mesh are very very poor here (comparing to 3ds MAX).

 

However, these are details, main question is: how to figure out exact volume of specific mesh?

I'm attaching a .dwg file of my project (this is very early stage).

 

Please help, I'm stuck with this for more than 2 days of intense manual-reading and googling.

005.dwg

... but I'm still not very good at 3d modeling, so I'm learning as I go.

....Tools to work with mesh are very very poor here (comparing to 3ds MAX).

 

How much training/experience with 3DS Max?

How much training/experience with AutoCAD?

 

Search here http://au.autodesk.com for past class Making a Mesh of Things.

Please help, I'm stuck with this for more than 2 days of intense manual-reading and googling.

 

I would recommend at least 6 months to learn the ins and outs of tackling something this complex.

Well, I attended 3ds MAX classes 8 years ago, I still remember some things, did some work on my own, but nothing professional.

 

I have worked with AutoCAD for about a year, few tutorials, and then self-learning as I did my previous ship project (which eventually I built in reality). But it was only in 2d, and not very complex.

 

Now that I started this new project, I decided to take a step further. I completed all the tutorials in http://www.we-r-here.com/cad/tutorials/index.htm in about a week, but it practically never gets to complex 3d modeling and calculations.

 

So if you know any good tutorials on 3d modeling, please tell.

 

But for now, can you help me with that volume calculation? How should I do it?

Tools to work with mesh are very very poor here (comparing to 3ds MAX).

Bingo. AutoCAD is (in my opinion) one of the worse programs to use for modeling and editing meshes, and my opinion includes the latest releases of AutoCAD that has shown a great increase in mesh support. Mesh modeling should be tackled using a NURBS based program, such as Rhino or 3DS Max. Meshes do not contain volumetric information that I have ever known. I'm sure there's ways to calculate mass, but not out of the box.

 

I'd hate to be the bearer of bad news but continuing to use AutoCAD for meshes will push you further down the rabbit hole. Have you tried using solids at all? I've managed to do some pretty advanced 3D modeling with solids. Not trying to toot my own horn here, but in a recent post in the Showcase forum I was showing off me modeling a guitar I own here: http://www.cadtutor.net/forum/showthread.php?71752-Modeling-my-Fender-Squier-Stratocaster-fun-project-for-me

 

Everything you see there is by means of solids, not meshes. If you think that what I have done using solids can be utilized in designing your hull, then I'd be glad to help (among plenty others) guiding you along. All you would need to do is give a good example of where you want to end up, and we'll help you on the approach and continual procedures using a slew of solid modeling techniques.

This looks like an interesting project.

 

I’ve included a file that demos a couple of options.

 

The original geometry did require correction. The geometry also suggests that symmetry is desired.

 

If that is correct then the green model (actually block inserts) offers some interesting possibilities. Via the BEDIT command, one quadrant of the model can be isolated in AutoCAD’s Block Edit Mode. This will allow modification to the base geometry - so, for instance, the solid’s vertices can be stretched (similar to mesh editing) by setting the correct selection filter (SUBOBJSELECTIONMODE).

 

Any change to this Block geometry will, when saved, propagate through all four sections.

 

The MASSPROP command, used in Block Editing mode, will give a volume that can be multiplied by 4 to account for the entire model.

Once the target shape and volume are achieved, the 4 blocks can be EXPLODEd back to Solids, then UNIONed together.

 

The red Solid was created by lofting the ribs (5 sections), using the “Ruled” option in the Loft Settings dialog. Use the MASSPROP command to get the solid’s volume.

005_Mod.dwg

Edited October 13, 2012 by SEANT
Corrected typo

Seant, you mean "MASSPROP". I know you know the command, but was mistyped. Just simply clarifying is all. And good use of the LOFT command in your modification. Exactly my point that solids can still be plenty powerful.

Good catch Tannar. And, I also agree, 3DSolids are the best.

...

So if you know any good tutorials on 3d modeling, please tell.

 

There are a bunch of 3D modeling tutorials in my signature (a little old - written for 2007). Whether they are any good or not.....

SEANT, thanks, that looks promising. I think I would stay with red one - seems easier to work with. But with it, being 3d Solid, how do add, delete, merge vertexes?

 

JD Mather, I will look into these tutorials, thanks.

 

StykFacE, your guitar looks very good. Really nice work. You asked what I want to end up, I can't show yet, but idea here is to design a hull shape that has needed hydrodynamics. Long time to explain, but basically I'll need to work with this basic shape, adding, deleting and merging vertexes, edges, faces, making it more and more complex, and keeping a look out for the volume. Then I'll export it to another hydrodynamics calculation program for fine tuning.

The shape will have symmetrical sides, but bow and stern will be different.

I'll need to work with this basic shape, adding, deleting and merging vertexes, edges, faces, making it more and more complex....

 

I think you would be better off leaving this workflow behind.

 

 

Edit: oops - was thinking one phrase and writing another. StykFacE correctly interpreted.

 

Check the tutorials in my signature using surfaces to edit solids.

Edited October 14, 2012 by JD Mather

Sorry, I did not understand your expression, what did you mean?

I think JD meant to say "leave this workflow behind", and I would agree. Editing vertices and faces aren't really a strong point of AutoCAD.

Okay, I see... Well, thanks. I'll try to learn solids, but I don't believe I will have much luck there.

Okay, I see... Well, thanks. I'll try to learn solids, but I don't believe I will have much luck there.

Why would you think you wouldn't have any luck? You do realize you can edit solids with much more ease than every before in more recent versions of AutoCAD, correct?

 

For instance:

Sub-Object Selection Modes: http://exchange.autodesk.com/autocad/enu/online-help/search#WS73099cc142f487551d68dd061249d36330f-7db4.htm

Using Grips: http://exchange.autodesk.com/autocad/enu/online-help/search#WS1a9193826455f5ffa23ce210c4a30acaf-6763.htm

Loft/Sweep profile edits: http://exchange.autodesk.com/autocad/enu/online-help/search#WS1a9193826455f5ffa23ce210c4a30acaf-67aa.htm

 

You still can go with mesh if you'd like, nobody is telling you not to. We're just hinting that you may have better luck (and easier) if you approached using Solids if you've chosen AutoCAD as your program of choice.

 

You can get the Volume of a Mesh with an app called "Polyhedral Mesh to Solid", it's in the AutoCAD apps exchange. You get a trial period with it. It will also convert your Mesh to a Solid.

I figured something existed. Seems like a popular request/need.

Well... It's just that for example I have the shape I need (like that mesh I provided before) and I need to divide some face, or add a line, because I need to make the model more complex. How do I do that with Solids?

This all depends. Can you give us what you have, and where you want to end up? When you say "more complex", that is too broad of a request. If you can give us an end result (or a best example) then it can help us guide you along.

 

But, just to get you started, there are a few ways to do this. Rotating the UCS and realigning the drawing space to PLAN is one way to manipulate the drawing area to get an area prepped for more detailed work. Also, the Dynamic UCS can work, but mainly on flat plane/surfaces. You can utilize the Imprint and Presspull commands. I also use Interfere command a lot to "combine" 3D solids into more complex solids.

 

There's a ton more, so just give us a bit more info and we can help you out.

Okay. Take the file I had before (005.dwg).

 

First of all, how do I make this shape in Solid mode from the beggining?

Next, I need to connect the nose of that hull into sharp one. Now there is a flat surface at the end of the hull, but I need it sharp. How do I do that?

I suggest you create your cross sections very carefully. ensuring they are symmetrical, by using the MIRROR command to reflect them across the keel.

You will likely want to make use of the POINT option within the LOFT command for the bow.

Well, you see, problem is, I don't know the exact shape of cross sections yet. I started with a extruded triangle, and here's where I got after adding more vertexes, lines and faces. I don't know how the final shape will look like, I need to experiment, add, remove, join, divide these vertexes, lines and faces to see what will finally work.