Build A Trimmed Mesh

Slide 3

Create the constraint relationship.

Create The Constraint Relationships

This series of instructions teaches you to create and manage constraint relationships. In the earlier exercise, you created 4 quadrants of terrain that overlap the grid. In this exercise, you've created a road that is overlapped by all 4 quadrants of terrain. Now it's time to set up the contraint relationships.

  1. Left click the mesh node named RoadMesh and select Edit » Copy To Link from the main menu.
  2. Open \SCENOMICS\EXERCISES\DISPLACEMENT\TERRAIN_1x1.
  3. Examine the hierarchy: This is a picture of the hierarchy.
  4. The sweep is diplaced.
  5. Right click over the group node named Scene and select Create » Group from the listed options.
  6. Set the name of the group to Constraints.
  7. Select Edit » Paste From Link from the main menu.
  8. The software creates a link node as a child of Constraints.
  9. The worksheet looks like this: This is a picture of the worksheet.
  10. Examine the hierarchy and expand the group node named Constraints.
  11. The hierarchy looks like this: This is a picture of the hierarchy.
  12. There is a link node pointing to the mesh. The icon uses a mesh icon with a small × to indicate that it is a link node pointing at a mesh.

Create The Trimming Relationship

This series of instructions teaches you to create the trimming relationship.

  1. Examine the hierarchy.
  2. Let click the mesh node named Terrain_1x1.
  3. Hold down CTRL and left click the group node named Constraints.
  4. Both nodes are highlighted.
  5. Right click and select Create Trimming Relationship from the listed options.
  6. The hierarchy looks like this: This is a picture of the hierarchy.
    The software adds a DelaunayTrimModifier and links the trim modifier to the Constraints group. The software also adds a link to RoadMaterial to the palette group. Notice that the DelaunayTrimModifier is at the end of the construction history, coming after the PlanarProjectModifier.
  7. The worksheet looks like this: This is a picture of the worksheet.
    You can see the UV parameters for the mesh have been destroyed. This is because of the way trimming performs mesh integration. This is relatively easy to fix in this example.
  8. Examine the hierarchy and left click DelaunayTrimModifier.
  9. Now drag it up and to the left of PlanarProjectModifier.
  10. Release the left mouse button when PlanarProjectModifier highlights.
  11. The hierarchy looks like this: This is a picture of the hierarchy.
  12. The worksheet looks like this: This is a picture of the worksheet.
    The UV values have been restored. This is because the PlanarProjectModifier is linked to TrailMaterial. The PlanarProjectModifier automatically applies UV values to any faces using TrailMaterial but not faces using the road material. This works for a single material - if your mesh has multiple materials before trimming you will have to do some "fixing". However best modeling practice involves setting up all your constraint trimming before moving on to perform other modeling operations.
  13. Save your work.
  14. Right click over the group node named Constraints and select Toggle Visible from the listed options.
  15. Select Worksheet » Global Edges from the listed options.
  16. Feel free to move around the scene.

Create Additional Trimming Relationships

Use the exact same procedure to create trimming relationships for TERRAIN_1x2, TERRAIN_2x1, and TERRAIN_2x2. This allows you to use one road mesh to trim against all the terrain meshes. The road mesh is neatly clipped, including UV values, to each terrain mesh. Changes to the road mesh can be easily propagated into each terrain mesh. Or you can skip this part and move on to the next stage of this exercise.