SMS:Merge 2D Meshes: Difference between revisions

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Two meshes can be merged to form a new mesh which will be called "Merged" (or something similar if that name is already used)in the ''Project Explorer''.  No model data will be transferred, and the type of the new mesh will be the same as the default mesh model set in the user [[SMS:Preferences|Preferences]] regardless of the model type of the meshes used in the merge. (To check the user preferences, go to  ''Edit''|'''Preferences...'''  and check the ''Startup'' tab).  This option is accessed by selecting two meshes and right-clicking and then selecting '''Merge 2D Meshes'''.
==Merge Command==
Two meshes can be merged to form a new mesh which will be called "Merged" (or "Merged (##)" if that name is already used)in the ''Project Explorer''.  No model data will be transferred, and the type of the new mesh will be the same as the default mesh model set in the user [[SMS:Preferences|Preferences]] regardless of the model type of the meshes used in the merge. (To check the user preferences, go to  ''Edit''|'''Preferences...'''  and check the ''Startup'' tab).  This option is accessed by selecting two meshes and right-clicking and then selecting '''Merge 2D Meshes'''.


A merged mesh will be generated if and only if the meshes do not overlap except on nodes and element edges that are on the border of the other mesh.  Overlapping element edges can only be on the border of the mesh and must have nodes at the same location.  Disjoint nodes of one mesh that are inside the area of the other mesh will cause the merge to be prevented.  A pair of meshes are also invalid for merging if the centroid of an element in one mesh is within the area of an element in the other mesh.
If the two meshes being merged overlap, SMS will report this to the user and give the option of aborting the merge.  


===Examples of Meshes that will merge===
When merging two meshes that overlap, SMS includes all nodes from both meshes, and forces one previous mesh boundaries to be honored in the merged mesh.  Any disjoint nodes in the meshes will be deleted.
 
==Merging with Priority==
One common feature that may be desired would be only include nodes from one of the two meshes in the overlap region.  This feature is under consideration.  To get this result with current functionality, the following steps may be followed:
 
# Convert the boundary of the mesh with higher priority (the one for which the nodes will be preserved) to a feature polygon (Use the right click|Convert to feature command).
# Build polygons for the new regions just created in the map coverage.
# Using the Nodes|Options command in the mesh module, make sure the option to retriangulate voids is enabled.
# Select the polygons created in the previous step.
# In the Edit menu, use the ''Select/Delete Data'' command to select all the nodes from the low priority mesh that lie inside the high priority mesh.  Delete these nodes.
# Now merge the two meshes.  The nodes from the low priority mesh that were in the overlap region have been deleted, so they do not appear in the merged mesh.
 
(Note: If you wish to maintain the original meshes in this process, you should create a copy of the low priority mesh to edit before performing the steps.  This copy can be deleted after the merge process if desired.)
 
 
===Examples of Meshes that are not considered overlapping===
{|
{|
|-
|-
|[[Image:ValidMerge1.jpg|thumb|left|200 px|Example 1: Mesh cells that can merge because they share the same element edge and nodes.]]
|[[Image:ValidMerge1.jpg|thumb|left|200 px|Example 1: Mesh cells that share the same element edge and nodes.]]
|[[Image:ValidMerge2.jpg|thumb|left|200 px|Example 2: Mesh cells that share the same node and do not overlap can be merged.]]
|[[Image:ValidMerge2.jpg|thumb|left|200 px|Example 2: Mesh cells that share the same node and do not overlap.]]
|-
|-
|colspan="2"|[[Image:ValidMerge3.jpg|thumb|left|250 px|Example 3: Mesh cells that can merge because they do not overlap.]]
|colspan="2"|[[Image:ValidMerge3.jpg|thumb|left|250 px|Example 3: Mesh cells that do not overlap.]]
|
|
|}
|}


===Examples of Meshes that will not merge===
===Examples of Meshes that are considered overlapping===
{|
{|
|-
|-
|[[Image:NoMerge1.jpg|thumb|left|175 px|Example 1: Mesh cells that will not merge because they are overlapping.]]
|[[Image:NoMerge1.jpg|thumb|left|175 px|Example 1: Mesh cells that are overlapping without no shared nodes.]]
|[[Image:NoMerge2.jpg|thumb|left|150 px|Example 2: Mesh cells that will not merge because they overlap and do not share the same element edges and nodes.]]
|[[Image:NoMerge2.jpg|thumb|left|150 px|Example 2: Mesh cells that overlap and share an element edge and nodes.]]
|[[Image:NoMerge3.jpg|thumb|left|225 px|Example 3: Mesh cells that will not merge because they do not share the same nodes in the same location.]]
|[[Image:NoMerge3.jpg|thumb|left|225 px|Example 3: Mesh cells that have common portions of an edge.]]
|-
|-
|[[Image:NoMerge4.jpg|thumb|left|200 px|Example 4: Mesh cells that will not merge because they do not share the same nodes.]]
|[[Image:NoMerge4.jpg|thumb|left|200 px|Example 4: Mesh cells that have common portions of an edge.]]
|colspan="2"|[[Image:NoMerge5.jpg|thumb|left|275 px|Example 5: Mesh cells that will not merge because a disjointed node of one mesh is with in the area of the second mesh.]]  
|colspan="2"|[[Image:NoMerge5.jpg|thumb|left|275 px|Example 5: Mesh with a disjointed node inside of the second mesh.]]  
|}
|}


Revision as of 15:52, 16 September 2014

Merge Command

Two meshes can be merged to form a new mesh which will be called "Merged" (or "Merged (##)" if that name is already used)in the Project Explorer. No model data will be transferred, and the type of the new mesh will be the same as the default mesh model set in the user Preferences regardless of the model type of the meshes used in the merge. (To check the user preferences, go to Edit|Preferences... and check the Startup tab). This option is accessed by selecting two meshes and right-clicking and then selecting Merge 2D Meshes.

If the two meshes being merged overlap, SMS will report this to the user and give the option of aborting the merge.

When merging two meshes that overlap, SMS includes all nodes from both meshes, and forces one previous mesh boundaries to be honored in the merged mesh. Any disjoint nodes in the meshes will be deleted.

Merging with Priority

One common feature that may be desired would be only include nodes from one of the two meshes in the overlap region. This feature is under consideration. To get this result with current functionality, the following steps may be followed:

  1. Convert the boundary of the mesh with higher priority (the one for which the nodes will be preserved) to a feature polygon (Use the right click|Convert to feature command).
  2. Build polygons for the new regions just created in the map coverage.
  3. Using the Nodes|Options command in the mesh module, make sure the option to retriangulate voids is enabled.
  4. Select the polygons created in the previous step.
  5. In the Edit menu, use the Select/Delete Data command to select all the nodes from the low priority mesh that lie inside the high priority mesh. Delete these nodes.
  6. Now merge the two meshes. The nodes from the low priority mesh that were in the overlap region have been deleted, so they do not appear in the merged mesh.

(Note: If you wish to maintain the original meshes in this process, you should create a copy of the low priority mesh to edit before performing the steps. This copy can be deleted after the merge process if desired.)


Examples of Meshes that are not considered overlapping

Example 1: Mesh cells that share the same element edge and nodes.
Example 2: Mesh cells that share the same node and do not overlap.
Example 3: Mesh cells that do not overlap.

Examples of Meshes that are considered overlapping

Example 1: Mesh cells that are overlapping without no shared nodes.
Example 2: Mesh cells that overlap and share an element edge and nodes.
Example 3: Mesh cells that have common portions of an edge.
Example 4: Mesh cells that have common portions of an edge.
Example 5: Mesh with a disjointed node inside of the second mesh.

Related Topics


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SMS – Surface-water Modeling System
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