Suggested Technique for Redefining Imported Surfaces

The following describes the recommended procedure for redefining imported surface geometry in Release 17.0. It assumes that the IGES file has already been created and imported into Pro/ENGINEER.

Procedure
  1. The goal of this process is to obtain the completed surface quilt shown in Figures 1 and 2 from the imported IGES data shown in Figure 3.

    Figure 1

    Figure 2

    Figure 3

  2. In the PART menu select Feature, Redefine, and the import feature. In the REDEF IMPT menu select Fix Bndries, Zip Gaps, Auto Select to select the edge chains highlighted in blue in Figure 4.

    Figure 4

  3. In the SEL CHAINS menu select Zip Gaps to view the proposed changes necessary to join the selected edges. The red mesh lines are present to allow better visualization of the surfaces.

    Figure 5

  4. In the ACCEPT FIX menu select Accept to finish zipping the selected gaps.

    Figure 6

  5. The Message Window presents the following information: "WARNING: Design intent is unclear. Use "Geom Check" menu for details." In the SEL CHAINS menu select Geom Check. Figure 7 shows a surface highlighted in red and an edge of that surface highlighted in cyan. In the SHOW ERRORS menu select Item Info. The Information Window appears with the following message: "The two highlighted surfaces are coincident for all or a portion of their geometry, including the highlighted edge. You will probably want to delete one coincident surface to avoid creating a zero volume region when surfaces are joined." What you see is not one surface highlighted in red. There are actually two surfaces right on top of each other highlighted in red, and the edge highlighted in cyan is one area of the two surfaces that is coincident.

    Figure 7

  6. In the SHOW ERRORS menu select Next Item to view the next diagnostic. Figure 8 shows a chain of two edges highlighted in green. Select Item Info. The Information Window appears with the following message: "Incompatible surface orientation prevents the highlighted surfaces/edges from joining correctly. Check and correct all other Geom Checks for duplicate or overlapping surfaces which might have caused an incorrect set of surfaces to be joined. You may want to consider deleting a portion of that geometry and recreating it in Pro/ENGINEER." Notice that the two coincident surfaces are joined to each other along their top boundary.

    Figure 8

  7. In the REDEF IMPT menu select EXCLUDE SRFS and one of the two coincident surfaces. In the EXCLUDE SRFS menu select Done. Figure 9 shows the import feature after regeneration. Notice that one of the two coincident surfaces is entirely outlined in yellow, i.e. it has been excluded from joining into the quilt. Also note that the chain highlighted in green in Figure 8 is now joined.

    Figure 9

  8. In the PART menu select Layer, Set Items, and use the Quilt option to add the excluded surface to a layer that is blanked. Figure 10 shows the current status of the import feature. Notice that there are still three areas that need to be addressed.

    Figure 10

  9. Figure 11 shows an untrimmed surface that is currently too large to join into the quilt.

    Figure 11

  10. In the REDEF IMPT menu select Fix Bndries, Edit Bndry, and the untrimmed surface. In the CHAIN OPT menu select Select All. Figure 12 shows the entire contour of the untrimmed surface ready to be edited.

    Figure 12

  11. In the EDIT BNDRY menu select Create, Project. Figure 13 shows three edges highlighted in blue that will be projected onto the untrimmed surface.

    Figure 13

  12. In the GET SELECT menu select Done Sel to create the inner chain of orange edges shown in Figure 14.

    Figure 14

  13. In the EDIT BNDRY menu select Delete. Select the four segments belonging to the outer loop of orange edges. Figure 15 shows the results. Notice that the original yellow contour of the untrimmed surface is still present. This is the case until the replacement of the original contour with the new orange contour is completed successfully.

    Figure 15

  14. In the EDIT BNDRY menu select Create, Connect. Select the two red vertices at the ends of the orange chain. In the GET SELECT menu select Done Sel. Figure 16 shows the orange loop that has just been completed by the addition of the top segment. Notice that the red vertices in Figure 15 are now orange. The ends of chains are indicated by red crosses and internal vertices are indicated by orange crosses.

    Figure 16

  15. Figure 17 shows the replacement contour highlighted in red upon selecting Preview. This indicates that the current contour can be used to replace the original contour. Figure 18 shows the replacement of the original contour upon selecting Done. Notice how the surface has been trimmed so it fits properly into the quilt. Also note that the surface has not been joined into the quilt because we have not yet returned from the editing process and allowed the regeneration of the import feature.

    Figure 17

    Figure 18

  16. Figure 19 shows the current status of the import feature. The next area to be addressed is shown in Figure 20. The red mesh lines on the surface are isolines. Isolines represent the two main directions of surface creation. A surface can be meshed by selecting View, Cosmetic, Mesh Surface. Notice that the yellow edges belonging to the surrounding surfaces are very similar to the red isolines. Edge and vertex misalignment is common to imported surfaces. It is frequently the case that if surfaces were trimmed along isolines, more surfaces would join together automatically.

    Figure 19

    Figure 20

  17. In the SELECT SURF menu select Sel Surface and the meshed surface. In the CHAIN OPT menu select Select All. Figure 21 shows the original contour ready to be edited.

    Figure 21

  18. In the EDIT BNDRY menu select Modify, Move Vertex. Select the upper left orange vertex and use Query Sel to place it at the upper left "end of edge". Figure 22 shows the resulting contour. Figures 23-25 show the contour after moving the lower left, lower right, and upper right vertices in the same manner.

    Figure 22

    Figure 23

    Figure 24

    Figure 25

  19. Figure 26 shows the replacement contour highlighted in red upon selecting Preview. Figure 27 shows the replacement of the original contour upon selecting Done. Notice how the edges and vertices have been aligned so the surface fits properly into the quilt. Also note that the surface has not been joined into the quilt because we have not yet returned from the editing process and allowed the regeneration of the import feature.

    Figure 26

    Figure 27

  20. Figure 28 shows the current status of the import feature. The next area to be addressed is shown in Figure 29. Notice that the yellow edges belonging to the adjacent surfaces are very similar to the red isolines.

    Figure 28

    Figure 29

  21. In the SELECT SURF menu select Sel Surface and the meshed surface. In the CHAIN OPT menu select Select All. Figure 30 shows the original contour ready to be edited. Notice the extra vertices in the top, right, and bottom edges and the poor quality of the left edge. Edge fragmentation is common to imported data and can lead to extra, unnecessary surface patches when the edges are referenced in sweeps or blends.

    Figure 30

  22. In the EDIT BNDRY menu select Modify, Merge Edges. Select the two orange vertices at either end of the bottom edge and in the CHOOSE menu Accept the chain highlighted in red in Figure 31. Figure 32 shows the resulting edge.

    Figure 31

    Figure 32

  23. In the MODIFY EDGS menu select Merge Edges. Select the two orange vertices at either end of the top edge and in the CHOOSE menu Accept the chain highlighted in red in Figure 33. Figure 34 shows the resulting edge.

    Figure 33

    Figure 34

  24. In the MODIFY EDGS menu select Straighten. Select the two orange vertices at either end of the left edge and in the CHOOSE menu Accept the edge highlighted in red in Figure 35. Figure 36 shows the resulting edge. Notice that the new edge does not appear to be straight in this view. The edge does, however, connect the two selected vertices with a straight segment that conforms to the shape of the surface.

    Figure 35

    Figure 36

  25. In the MODIFY EDGS menu select Straighten. Select the two orange vertices at either end of the right edge and in the CHOOSE menu Accept the chain highlighted in red in Figure 37. Figure 38 shows the resulting edge.

    Figure 37

    Figure 38

  26. Figure 39 shows the replacement contour highlighted in red upon selecting Preview. Figure 40 shows the replacement of the original contour upon selecting Done. Notice how the edges have been aligned so the surface fits properly into the quilt. Figure 41 shows the current status of the import feature. Also note that the three surfaces that have been edited are not yet joined into the quilt.

    Figure 39

    Figure 40

    Figure 41

  27. In the SELECT SURF menu select Done-Return to regenerate the import feature. Notice in Figure 42 that after returning from the editing process, all surfaces have been joined into the quilt.

    Figure 42

  28. In the REDEF IMPT menu select Fix Bndries, FixQuiltBndry. Figure 43 shows the edge chains that have been automatically selected. FixQuiltBndry proposes the automatic replacement of these chains/edges that are nearly tangent and almost an isoline with isolines of the surfaces. Note that FixQuiltBndry searches all one-sided edges in the import feature for selection (including those that belong to excluded surfaces).

    Figure 43

  29. Figure 44 shows an edge chain along the top of the surface that has been selected for replacement. Notice that chain ends are indicated by red crosses and internal vertices are indicated by orange crosses. In the FIXQULTBNDRY menu select Done. Figure 45 shows the surface with the highlighted chain replaced. To view the changes, in the REDEF IMPT menu select Fix Bndries, Edit Bndry, the surface, and From-To in the CHAIN OPT menu. Figure 46 shows the vertices available for chain selection. Notice that there is no longer an internal vertex along the top edge.

    Figure 44

    Figure 45

    Figure 46

  30. In the REDEF IMPT menu select Fix Bndries, FixVertices. Figure 47 shows that there are no badly aligned vertices present in this quilt.

    Figure 47

  31. In the FIX OPTIONS menu select Fix Tangency, Auto Select. The two-sided edge chains that were selected are highlighted in blue in Figure 48. The one remaining magenta chain was not selected because its dihedral angles are larger than the default MaxDihedral value of 10 degrees. To check the dihedral angle of two-sided edges, in the MAIN menu select Info, Srf Analysis, Max Dihedral.

    Figure 48

  32. In the SEL CHAINS menu select FixTangency to view the proposed changes necessary to establish more consistent tangency between surfaces.

    Figure 49

  33. In the ACCEPT FIX menu select Accept to finish setting tangency. To view the improvements, check the resulting dihedral angles as described above in step 31. Figure 50 shows the final state of the imported surfaces.

    Figure 50

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