I have a simple car for bullet, rolled down a hill, so it needs pivot constraints. I believe I have everything set up correctly; the axis should be X for both the Actor1 and Actor2 slots [1,0,0]. its not working right the wheels turn sideways, which means, either my pivots are not setup correctly, or the pivot is broken? or I just don’t understasnd how pivots work (I did try the Z axis cause figure maybe something was flip flopped but it didn’t work either).If anyone has a minute to take a look at this quick car rig, it would be appreciate! TD build 2025.33070
Setting the car body’s hinge axis of each constraint to [0,1,0], or disabling it altogether (ie. setting hinge axis to [0,0,0]) seems to resolve the issue:
However, I would expect the X axis of the car body to work for this case, so this solutions seems more like a work-around to the problem. This example is very similar to the “driving car” snippet which works as expected with the two axes of the constraint set to the same per body, so I’m not sure what’s different in this case. I’ve logged this as a bug internally for further review.
thanks, yea 0,0,0 seems to worked…I couldn’t quite identify this as a bug vs a user error. I can’t pinpoint why the snippet example works and mine did not. I tried a few things Y and Z axis and also flipped the actor1 and actor2 from chassis to wheel, and wheel to chassis with no luck either. as far as I could tell that order didn’t matter and have not hit on the thing that does.
I suppose the main difference with the OP snippit is the wheels are all contained within 1 actor as opposed to each wheel in it’s own actor, so the actor bodies number is used in the constraint rig. however I don’t see how that would matter, the rig still fails if its only got one wheel. but it is the main point of differentiation.
Tangent thought, but if you are going in to look more closely at this, it would be nice if the constraint guide geometry could be viewed in the main 3D viewport; this would just help check against pivots and axes with the main geometry. Quality-of-life improvement. I suspect this might be a pivot isue against the worldspace postion but its pretty hard to diagnose this.
@eric.b Ok I found the issue. It may not technically be a “bug”… The chassis collision type was the culprit. I suppose the oriented bounding box caused an issue where the pivot constraint doesn’t know which axis is which, or it allowed flipping of the hinge constraint. If I set the chassis collision shape to “Axis Aligned, or Convex Hull,” both work as expected in X or Z or whatever orientations. It may still be a bug that the constraint doesn’t work with an oriented bounding box. I still can’t fully explain it. but I can now reproduce it, all you have to do is open the operator snippit example for car and change the chassis to oriented bounding box and you will see the above behavior.
Thank you for digging into this further, that information was helpful. I’ve fixed the hinge constraint axis bug and the fix will be in the next official build we release: 2025.33290+. Thanks for the report.
