Knowledge Base

Article Number: 68 | VC4 | VC3 | Post Date: July 24, 2018 | Last Updated: July 24, 2018

When I add axles to my imported vehicle model, the wheels aren’t centered with respect to the centerline of the vehicle. How can I fix this? 

Occasionally a third-party vehicle mesh will either be oriented improperly and/or its “pivot point” will not be placed along the true centerline of the vehicle (along the vehicle’s x-axis). When this occurs, you will have two potential problems when creating a vehicle model:

(1)    The wheels will appear to not be oriented correctly with respect to the mesh.
(2)    The wheels will not be centered with respect to the centerline of the vehicle (the vehicle’s x-axis). 

The first issue occurs because every object in Virtual CRASH has its own local reference frame. When you add wheels to an object, Virtual CRASH will align the wheels with the object’s x-axis. So, you must first make sure your third-party mesh is properly aligned with the vehicle model’s x-axis. This is reviewed in the KB post:

The second issue is related to pivot point of the third-party model not being aligned with the true centerline of the vehicle. An example of this is shown below.

When the add axle feature is used for a rigid body object, Virtual CRASH will automatically place the wheels equally spaced with respect to the object’s centerline, but by default is assumed to fall along the pivot point of the imported model. So, if the pivot point of the imported model is away from the true centerline, you will have the issue of wheels being off center. One way to fix this issue for any imported model is to export your model to .vcm format, then drag-and-drop the .vcm file onto an existing model. Virtual CRASH will simply use the new polygon mesh for the existing vehicle model, without changing any other parameters. This guarantees your vehicle’s centerline remains symmetric no matter how the original third-party mesh defined the pivot point. This method is used in Chapter 7 of the User’s Guide.  

In the video below, we review how to create a wheelchair object by adding axles to a rigid body object. Fixing problems (1) and (2) above is demonstrated. 

Tags: Wheels not centered, center wheels, rigid body object, adding wheels, add axle, axles, axle alignment, wheel alignmnet.  

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