Space Grant Consortium - University of Wisconsin - Green Bay

Figure 4. Convex decomposition collision geometry used for each track shoe
The manual convex decomposition used as few convex hulls as possible that still accurately
described the collision geometry. This was done by studying animations of the original excavator
simulations to determine the surfaces on the track shoe that are actively in contact with other
bodies during the simulation. Figure 3 shows both the top and bottom surfaces of the track shoe
that are in active contact with other bodies as a darker shade. The white (or lightly shaded)
surfaces saw no contact during the simulation and were omitted in the final collision shape.
Figure 4 shows the final collision shape used for the track shoe body in the ChronoEngine
simulations.
A similar convex decomposition technique is applied to the two gears of the drive sprocket. Only
the sections of the geometry that are actively colliding with other bodies during the simulation
are included in the collision shape. In this case, each convex gear tooth is used as a collision
object which is rigidly attached to the base body of the drive sprocket. Once the correct collision
geometry was created for the track shoe and gear, it was applied to each appropriate body and the
entire model was ready for simulation in ChronoEngine (Figure 5).
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