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Modifying the geometry of a structure
Posted 2 sept. 2010, 03:59 UTC−4 3 Replies
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How can I display a fine mesh in draw mode with axis labels visible in all views (3-D, XY, YZ etc) please?
If I draw some 3-D structures, and then want to create subdomains for meshing purposes or modifying the structure, its very difficult to figure out the lengths in order to match to the existing solids. I end up using a ruler to measure the structures on the screen.
I have turned on everything I could find in options -> Axis/Grid settings and set the mesh size to "fine" in options->selection/visualisation settings but all I get is a very coarse mesh along the outer boundaries, so coarse as to be useless for measuring the dimensions and selective units (so that for example even though my structure is in micro meters in all dimensions, only one axis has the qualification x10e-6). Changing the mesh size in options->selection/visualisation settings from coarse to normal to fine has no effect. Is this a bug? I need a fine 3-D mesh that permeates the entire structure to figure out the distances.
Also, what is the difference between a solid and a face in the block specification dialog please? From the glossary, I get the following:
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solid
A description of a part of the modeling space. See also subdomain.
solid modeling
A 3D geometry modeling method that describes both the boundary and interior of the geometry using solid objects. See also constructive solid geometry (CSG) and solid.
solid object
A geometry object representing one or several solids.
face, face segment
A domain describing a bounded part of a surface in a 3D geometry. A face or face segment is a boundary in a 3D geometry. See also domain.
face object
A geometry object with no topological information on subdomains. Typically a trimmed surface is represented as a face object.
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It seems to that a face is a surface based on these definitions. However when I select "face" in the Block dialog box in draw mode, I still get a solid block. Can I not create a surface in a 3-D structure to partition existing objects?
Finally, is there no way that I can drag and resize objects in 3-D like I can in 2-D? Do I always have to specify this in a dialog box?
Thanks in advance.
Read more: Displaying mesh in draw mode - COMSOL www.comsol.com/community/forums/analyzing-geometry/thread/9044/#ixzz0yMBvvmFf
If I draw some 3-D structures, and then want to create subdomains for meshing purposes or modifying the structure, its very difficult to figure out the lengths in order to match to the existing solids. I end up using a ruler to measure the structures on the screen.
I have turned on everything I could find in options -> Axis/Grid settings and set the mesh size to "fine" in options->selection/visualisation settings but all I get is a very coarse mesh along the outer boundaries, so coarse as to be useless for measuring the dimensions and selective units (so that for example even though my structure is in micro meters in all dimensions, only one axis has the qualification x10e-6). Changing the mesh size in options->selection/visualisation settings from coarse to normal to fine has no effect. Is this a bug? I need a fine 3-D mesh that permeates the entire structure to figure out the distances.
Also, what is the difference between a solid and a face in the block specification dialog please? From the glossary, I get the following:
-------------------------------------------------------------------------------------------------------------
solid
A description of a part of the modeling space. See also subdomain.
solid modeling
A 3D geometry modeling method that describes both the boundary and interior of the geometry using solid objects. See also constructive solid geometry (CSG) and solid.
solid object
A geometry object representing one or several solids.
face, face segment
A domain describing a bounded part of a surface in a 3D geometry. A face or face segment is a boundary in a 3D geometry. See also domain.
face object
A geometry object with no topological information on subdomains. Typically a trimmed surface is represented as a face object.
-------------------------------------------------------------------------------------------------------------
It seems to that a face is a surface based on these definitions. However when I select "face" in the Block dialog box in draw mode, I still get a solid block. Can I not create a surface in a 3-D structure to partition existing objects?
Finally, is there no way that I can drag and resize objects in 3-D like I can in 2-D? Do I always have to specify this in a dialog box?
Thanks in advance.
Read more: Displaying mesh in draw mode - COMSOL www.comsol.com/community/forums/analyzing-geometry/thread/9044/#ixzz0yMBvvmFf
3 Replies Last Post 3 sept. 2010, 05:57 UTC−4
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Posted:
1 decade ago
Hi
You have too many questions there in one go, so I'll probably miss some, (and I do not have access to comsol here so I must work from my mind), but:
Metrology: use the ruler function, not the grids, that is: select a line, or two points and click the "ruler" icon left of the graphcical border in 3.5, then you will get dimensions (length or distance between points, or coordinates of a point.
Mesh visibility, you can change the visualisation options in the view preferenes (3.5 not shure where it has gone in V4 but its certainly there too)
You must understand the differences in geometry within COMSOL: in 3.5 while you draw you are in graphical CAD mode (same in V4 but BEFORE you pass the "finish" line) you draw graphical entities: points, lines (sur)faces, solids. Then you move to the FEM mode of graphics (i.e. you perform a "geomanalyse()" in 3.5 or pass the "graphical Finish line in V4. Now youre geometry has been combined and you have resulting domains, subdomains, lines and points, these are number indexed entitites to which you apply physics, mesh .... Theire definition is given in the doc depending if you are in 3D, 2D or 1, or 0D
Mesh can onbly be set on analysed and inexed geometry (as some CAD entities might dissapear as they have no sens in the defined mode, such as a single line stretching out over a surface of a domain, the surface will be split but the excessive line will dissapear (if you are in 3D mode, as orphans are ignored)
Hope this helps on the way
--
Good luck
Ivar
You have too many questions there in one go, so I'll probably miss some, (and I do not have access to comsol here so I must work from my mind), but:
Metrology: use the ruler function, not the grids, that is: select a line, or two points and click the "ruler" icon left of the graphcical border in 3.5, then you will get dimensions (length or distance between points, or coordinates of a point.
Mesh visibility, you can change the visualisation options in the view preferenes (3.5 not shure where it has gone in V4 but its certainly there too)
You must understand the differences in geometry within COMSOL: in 3.5 while you draw you are in graphical CAD mode (same in V4 but BEFORE you pass the "finish" line) you draw graphical entities: points, lines (sur)faces, solids. Then you move to the FEM mode of graphics (i.e. you perform a "geomanalyse()" in 3.5 or pass the "graphical Finish line in V4. Now youre geometry has been combined and you have resulting domains, subdomains, lines and points, these are number indexed entitites to which you apply physics, mesh .... Theire definition is given in the doc depending if you are in 3D, 2D or 1, or 0D
Mesh can onbly be set on analysed and inexed geometry (as some CAD entities might dissapear as they have no sens in the defined mode, such as a single line stretching out over a surface of a domain, the surface will be split but the excessive line will dissapear (if you are in 3D mode, as orphans are ignored)
Hope this helps on the way
--
Good luck
Ivar
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Posted:
1 decade ago
Hi,
Many thanks for your reply. I did experiment with the ruler function before I posted but found it to be hardly useful. What I had been hoping for was a drawing mesh (not to be confused with the computational mesh) in Draw mode, to assist in drawing of solid shapes. I guess this is not possible. Currently I draw the structure manually on graph paper in elevation and plan and transfer it using the GUI.
The reason I am struggling so much with the geometry is I am trying to construct a regular structured mesh, but I will post that query with an appropriate title in a different thread.
Thanks, Dinesh
Many thanks for your reply. I did experiment with the ruler function before I posted but found it to be hardly useful. What I had been hoping for was a drawing mesh (not to be confused with the computational mesh) in Draw mode, to assist in drawing of solid shapes. I guess this is not possible. Currently I draw the structure manually on graph paper in elevation and plan and transfer it using the GUI.
The reason I am struggling so much with the geometry is I am trying to construct a regular structured mesh, but I will post that query with an appropriate title in a different thread.
Thanks, Dinesh
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Posted:
1 decade ago
Hi
For regular structured mesh, the easiest is t cut your volumes into as many as possible regular blocks, it adds a few internal boundaries but mostly that can be ignored, then you can also use the sweep mesh feature
--
Good luck
Ivar
For regular structured mesh, the easiest is t cut your volumes into as many as possible regular blocks, it adds a few internal boundaries but mostly that can be ignored, then you can also use the sweep mesh feature
--
Good luck
Ivar