HM-3680: Preserve a Shape With Cluster Constraints

In the tutorial, you will be changing the length of the cab while preserving the shape of the wheel. To facilitate the morphing process you will be employing constraint and symmetry.

When circular features are stretched, they become elliptical in shape. In some cases as in the wheels of a truck, this effect is not desirable. In such cases, using cluster constraints will allow you to translate the features, along with the morph, while maintaining its circular shape.

This exercise uses the truck.hm file, which can be found in the hm.zip file. Copy the file(s) from this directory to your working directory.


Figure 1.

Open the Model File

In this step, you will open the model file, truck.hm.

  1. Open the model file, truck.hm.
  2. Review the model.

Create a Coordinate System

In this step, you will create a coordinate system.

  1. From the menu bar, select Geometry > Create > Systems > Axis Direction.
  2. For origin, select the node with the tag origin.
  3. For x-axis, select the node with the tag x-axis.
  4. For xy-plane, select the node with xy-plane.
  5. Click create to create the coordinate system.
  6. On the toolbar, select XZ Right Plane View ().


    Figure 2.
  7. Click return to exit the panel.

Create and Split Morph Volume

In this step, you will create and split the morph volume.

  1. From the menu bar, select Morphing > Create > Morph Volumes.
  2. Switch the creation method to create morphvol.
  3. Set entity type to enclose elements.
  4. Select elems >> all.
  5. Set system to global system.
  6. Set buffer % to 5.
    The morph volume is created.
  7. Click create to create the morph volume.


    Figure 3.
  8. Click the split/combine subpanel.
  9. Toggle the operation to split mvols.
  10. Toggle to split the morph volume by edges.
  11. Toggle the type of split to single split.
  12. Set single split to 0.44.
  13. Select the morph volume in the graphics window.
  14. Click split to split the morph volume.
    The original morph volume is now split into two morph volumes.
  15. Click return to exit the panel.

Create a Symmetry

In this step, you will create a symmetry.

  1. From the menu bar, select Morphing > Create > Symmetries.
  2. For name=, type symm1.
  3. Under domain, check the box for morph volumes.

    Symmetry can be linked to either domains or morph volumes. In this exercise since you are dealing with morph volumes you will use the check to link the symmetry to the morph volume.

  4. Switch the symmetry type to 1 plane.
  5. For syst, select the coordinate system created in Step 4.2.
  6. Click create to create the symmetry.
    A 1 plane symmetry with a square symbol is created.


    Figure 4.
  7. Click return to exit the panel.

Morph the Part

In this step, you will morph the part.

  1. From the menu bar, select Morphing > Morph, then click the move handles subpanel.
  2. Switch the morphing mode to translate.
  3. Switch the along option to along xyz.
  4. Set the following values:
    • X val = 500
    • Y val = 0
    • Z val = 0
  5. Select two handles as shown in the following image.
  6. Click morph to morph the front half of the truck.
    The front end is stretched 500 units. Since the front wheels are also the part of the morph volumes they became elliptical after morphing. This is not desirable. You will undo this morphing, constrain the wheels and re-do it.


    Figure 5.
  7. Undo all morphs.

Create a Cluster Constraint

In this step, you will create a cluster constraint.

The front wheels, after morphing, become elliptical. To fix this issue, you will be employing a particular type of constraint, called a cluster constraint, which helps to keep the original shape of a portion of the model while morphing.

  1. From the menu bar, select Morphing > Create > Morph Constraints.
  2. Set name= to const2.
  3. Switch the constraint type to cluster.
  4. Select nodes >> by collector.
  5. Select comps >> by id.
  6. Use id= 1-8 and then press Enter.
  7. Click select to select the components.
  8. Click create to create the cluster constraint.
    The cluster constraints are created on the nodes of the selected components.


    Figure 6.
  9. Click return to exit the panel.
  10. In the Model Browser, right-click MorphingConstraint and click Hide to turn off the constraints.

Morph the Part

In this step, you will morph the part.

Repeat the procedure in Step 5 to morph the font of the truck by 500 units.
The front end is stretched 500 mm. The front wheels are moved in the morphing process while maintaining their circular shape.


Figure 7.

Using cluster constraints and morph volumes you are able to stretch the cab of the pickup without distorting the wheels.