Semi-Automated Cleanup Tools

Semi-Automated Cleanup Tools Clean up on models containing a large number of faces can be tedious. Cleanup Tools can semi-automate this process using virtual and real operations. Locate problem areas Suggest repair method Perform repair operation The Cleanup tools are available from the Tools menu in GAMBIT.

Semi-Automated Cleanup Tools Quickly identify, zoom in, highlight areas that cause connectivity and mesh quality problems. Appropriate tools to fix problems are given. Graphics color coding set to connectivity based coloring. Graphics window pivot set to mouse. Available Cleanup tools: Clean up Short Edges Clean up Holes Clean up Cracks Clean up Sharp Angles Clean up Large Angles Clean up Small Faces Clean up Hard Edges Clean up Fillets Clean up Duplicate Geometry Select cleanup Domain

Clean Up Short Edges Why clean up short edges? Short edges can cause meshing difficulties such as large cell size change, highly skewed cells. Tools to identify and highlight the problem spot Cleanup domain Select whole model or group Maximum length: upper limit Default: 10 × shortest edge in the Cleanup Domain Items List: candidates for cleanup operation based on Cleanup domain and Maximum length Current length: length of currently picked edge Update: updates the Items list Required when Maximum length is modified Zoom In/Out: quick auto zoom in on or from the picked items Auto: automatically zooms in on selected item

Clean Up Short Edges Tools to identify and highlight the problem spot Local: current item + all faces connected to it Visible: make everything else invisible Shade: shade the local objects Options to Apply Cleanup Tool Apply: applies appropriate fix to selected item A/N: (Apply/Next) applies appropriate fix to selected item and automatically picks the next item in the list. The view is changed. Auto: entire list is processes automatically (only works for the Method: Edge merge) Ignore: removes selected item from list and selects next item Restore: the list is restored

Clean Up Short Edges Methods to fix the problem spot Vertex connect (least common) Average location Preserve location: first vertex Preserve location: second vertex Edge merge Merge with (select edge) Face merge Faces to merge (select faces) Edge merge pre-selected when at least one vertex has only one other connected edge. Appropriate methods and applicable entities are often pre-selected, however users may edit them.

Clean Up Short Edges Before Cleanup, Face Contains a Short Edge v_edge.5 edge.6 v_vertex.7 edge.2 v_edge.7 Before Cleanup, Face Contains a Short Edge Virtual Face Created After Cleanup by Edge Merge

Clean Up Holes Why clean up holes? Volumes must be “air-tight.” Holes in faces must be repaired in order to properly define volumes. Holes in the model are internal edge loops that do not constitute external boundaries of a face (or faces) Tools to identify and highlight the problem spot and Options to Apply Cleanup Tool Similar to those for Cleanup Short edge Method to fix the problem spot Create Face from Wireframe Real and Virtual options available

Clean Up Holes Before Cleanup, Face Contains a Hole Virtual Face Created After Cleanup by Create Face from Wireframe

Clean Up Cracks Why clean up cracks in faces? Cracks in faces cause meshing difficulties as well as disconnects which do not permit volume definition. Tools to identify and highlight the problem spot Maximum angle between edges defining the crack (default is 20) Other tools similar to those for Cleanup Short edge Options to Apply Cleanup Tool Similar to those for Cleanup Short edge Method to fix the problem spot Connect edges Tolerance: maximum distance between edges to be connected

Clean Up Cracks The edges that define the crack share one vertex Virtual Face Created After Cleanup by Edge/Vertex Connect Before Cleanup, Faces are Disconnected at Vertices with a Gap edge.8 edge.4 vertex.5 face.2 face.1 v_edge.9 v_face.2 v_face.1 The edges that define the crack share two vertices Virtual Face Created After Cleanup by Edge Connect Before Cleanup, Face Contains a Crack edge.8 edge.4 face.2 face.1 v_edge.9 v_face.2 v_face.1

Clean Up Sharp Angles Why clean up sharp angles? Sharp angles cause meshing problems such as highly skewed cells and possible failure of meshing algorithms. Tools to identify and highlight the problem spot Maximum angle: default is 20 Other tools similar to those for Cleanup Short edge Options to Apply Cleanup Tool Similar to those for Cleanup Short edge Methods to fix the problem spot determined by face-face angle If face-face angle > 135: Merge faces If face-face angle < 135: Chop one face and merge truncated face with neighboring face. Distance: length of shortest boundary edge of truncated face θ face–face angle: 180 –   is the angle between the normals of the two faces (shaded in grey)

Clean Up Sharp Angles (Without Chop) Before Cleanup 3 faces (real or virtual) Virtual Virtual After Cleanup Merge with left face After Cleanup Merge with right face

Clean Up Sharp Angles (With Chop) Truncated face Merged face Distance Chop option face - face angle < 135 Tri-primitive Mesh: Cooper 1 of 8 Sharp Angles Merge edges

Clean Up Large Angles Why clean up large angles? Cleaning up large angles may help generate map mesh. Tools to identify and highlight the problem spot Maximum angle: default is 5 degrees Other tools similar to those for Cleanup Short edge Options to apply the Cleanup Tool Similar to those for Cleanup Short edge Method to fix the problem spot Merge faces

Clean Up Large Angles 170° Before cleanup After cleanup Two connected faces; face normals nearly parallel After cleanup One virtual face results from large angle cleanup operation

Clean Up Small Faces Why clean up small faces? Small faces can cause meshing problems (similar to short edges) Tools to identify and highlight the problem spot Maximum area: default value is 100 times the area of the smallest face in the Cleanup domain Items in the list contains all faces with areas less the maximum area Other tools similar to those for Cleanup Short edge Options to apply the Cleanup Tool Similar to those for Cleanup Short edge Methods to fix the problem spot: Merge face Collapse face Candidate Faces to merge: all bounding faces with a face-face angle > 135 pre-picked

Clean Up Small Faces Before cleanup After cleanup Small face causes meshing problems After cleanup One virtual face results from virtual merge operation

Clean Up Hard Edges Why clean up hard edges? Cleaning up hard edges will simplify meshing by removing excess constraints Hard edges are also known as dangling edges. Creation occurs: as a result of a face split when the split tool only partially intersects target face from STL or mesh import Tools to identify and highlight the problem spot and options to apply the cleanup tool similar to those for Cleanup Short edge Method to fix the problem spot Remove all hard edges

Clean Up Hard Edges Before cleanup After cleanup Face is split by a dangling (hard) edge After cleanup Virtual face with edge split

Clean Up Fillets Why clean up fillets? Cleaning fillets will relieve meshing difficulties by simplifying faces. This can facilitate generating map/submap meshes. Tools to identify and highlight the problem spot Maximum angle: specifies the maximum deviation from 90o for outward-pointing normals computed at the boundaries of the fillet face. Other tools similar to those for Cleanup Short edge Options to apply the Cleanup Tool Similar to those for Cleanup Short edge Methods to fix the problem spot Merge face Collapse face Candidate Faces Faces to merge: all bounding faces with a face-face angle > 135 pre-picked to collapse between: two opposite faces along the longest edges prepicked

After cleanup by face merge After cleanup by face collapse Clean Up Fillets Before cleanup Fillet face can cause meshing difficulty After cleanup by face merge One virtual face results from virtual face merge After cleanup by face collapse Fillet face is divided; each part is merged with its adjoining face (suitable for volume map mesh)

Cleanup Duplicate Edges Why clean up duplicate edges? Duplicate geometry can cause discontinuities in the mesh and unintentional non-conformal interfaces. Clean Up Duplicate Edges Includes edges which are coincident in part (T-junction connect).

Cleanup Duplicate Faces Two search options Topology-based All lower entities (edges or vertices) to be identical between the two faces. Centroid-based The centroids of the two faces should be within tolerance. Less accurate, but helpful in detecting duplicate faces with different lower topology. Method Connect faces Delete faces

Cleanup Duplicate Volumes Method Connect duplicate volumes Delete duplicate volumes Before cleanup (Four volumes) Duplicate Volumes After cleanup (Three volumes)

The Cleanup Domain is group2 Select Cleanup Domain Specifies the domain to which the geometry cleanup operations apply. Whole Model (default) Predefined geometry group The Cleanup Domain is group2

Where are the Problem Areas? Cleanup Demo Where are the Problem Areas? Fillet Short edge Faces can be merged Sliver face

Cleanup Steps Import the .iges file using the default settings (Make tolerant). Change color coding to connectivity. Blue edges (2 connections) indicate connected geometry. Apply Cleanup Tools (Virtual Geometry Created) Short Edges Holes Large Angles Fillets Mesh using the Cooper Tool Source faces