How to divide a volume

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oyh48@hotmail.com
Posts: 5
Joined: Mon Sep 18, 2023 2:58 am

How to divide a volume

Post by oyh48@hotmail.com »

Dear sir,

I want to divide a 3d cube by a 2d surface. The cube is 10mx10mx10m. The diving plane is 5 m above Z=0. I divided the volume via geometry>edit>divide>volume>split

But GiD said "Could not subdivide volume, check line 15 Try again".

My questions are
1. How to identify line 15 in my model ?
2. How to divide the volume ?
3. How to check if the volume has been divided into 2

Another question is, how to model a smaller volume embedded in a bigger volume ? If I mesh them, would it create duplication of smaller volume in a bigger volume ? Where can I find the similar example ?

Thank you.

Best regards,

ong
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Divide cube 1.gid.rar
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Error when diving volume.jpg
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User avatar
escolano
Posts: 1921
Joined: Sun Sep 05, 1982 10:51 pm

Re: How to divide a volume

Post by escolano »

The volume split tool do not find and create intersections curve-curve, curve-surface, and surface-surface,
all curves and surfaces must be subdivided before to used, then you must select a collection of surfaces that separate the volume in two or more regions.

1- To identify an entity knowing its id can use
Utilities->Signal->Lines
15
or View->Label->Selected ON->Lines
15

2- First must divide lines and surfaces and this require create intersections
e.g.
Geometry->Edit->Intersection->Surfaces
and select the surfaces you want, in this case can select all
surfaces_intersected.png
surfaces_intersected.png (17.56 KiB) Viewed 8547 times
then can split the volume in two selecting the first the volume and then the surface in blue

3- You will see in 'render normal' that there are two volumes, represented by the scaled cyan curves of its boundary. You can also list the entities to know what do you exactly have.
oyh48@hotmail.com
Posts: 5
Joined: Mon Sep 18, 2023 2:58 am

Re: How to divide a volume

Post by oyh48@hotmail.com »

Dear escolano,

After dividing all the surfaces, how to divide the volume ? How to show the volume is divided into 2 ?
question to gidD hub_Page1.jpg
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question to gidD hub_Page2.jpg
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question to gidD hub_Page4.jpg
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Can you tell me how to set the geometry such as yours ?
Untitledu.jpg
Untitledu.jpg (79.08 KiB) Viewed 8532 times
How to create volume that embeded into a box ? Do I need to carry out volume boolean operation ?

Thank you.

Regards,

ong
User avatar
escolano
Posts: 1921
Joined: Sun Sep 05, 1982 10:51 pm

Re: How to divide a volume

Post by escolano »

In my example, after intersect the surfaces I have send a surface to other layer, only to visually show you that the intersection of surfaces has also splitted this surface in two new surfaces pink and cyan (and I have set the layer of the volume transparent to see the inner surfaces)

You can just delete the pink surface (and its dependencies) that is unneeded,
and to divide the volume simply
Geometry->Edit->Divide->Volumes->Split
select the volume
and select the cyan surface (in render normal can be selected more easy, or you can set on/off layers to aid the selection, or enter the id if you know its number)

You can visually see that now there are two volumes, e.g. one is selected in red
two_volumes_one_selected.png
two_volumes_one_selected.png (20.05 KiB) Viewed 8515 times
to identify what do you have in your model
you can send entities to different layers, list them, set on its labels, change render normal/flat, etc.

And if now do you want to create a bigger volume embedding these two volumes, you can simply create this volume holed, creating the surfaces and then selecting in the creation the outer and inner(holes) surfaces,
or first create the outer volume and then edit it to add some hole (selecting other volumes to be its holes)

The GiD boolean operations are unrecommended:
They are non very robust and hard because will need to find and do the intersections of curves-curves, curves-surfaces, surfaces-surfaces, split curves and surfaces, detect parts inside/outside other parts, split volumes, delete parts...
It is much faster and robust simply use tools like "Hole volume" ,when you know that a volume is completely inside other volume and all previous steps are unneeded
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