Hi everyone,
I'm rigging a roller coaster train in Cinema 4D 2025 and running into two persistent issues. Would really appreciate any experience or advice.
THE SETUP
The train has four cars with five bogies total:
Car 1 has a front and rear bogie
Cars 2, 3 and 4 each have one rear bogie
The track system has three connected splines:
Track 01 — train moves forward
Track 02 — train reverses backwards
Track 03 — train moves forward again
Each bogie has three driver nulls (T1_CTRL, T2_CTRL, T3_CTRL), each with an Align to Spline tag linked to their respective track. An Xpresso network drives the ATS position values and switches constraint weights between tracks as the train progresses. This part is working correctly.
Each car body sits between its two bogies, controlled by a MID null with a Transform constraint averaging position and rotation between the front and rear bogie (50/50).
ISSUE 1 — RANDOM 180 DEGREE FLIPPING
Car 03 and Car 04 randomly flip 180 degrees at specific points along the track, particularly during Track 02 and Track 03. The flip is not consistent — it happens at specific Distance values and then corrects itself further along.
I believe this is a gimbal lock issue caused by the Transform constraint averaging rotations between two bogies. When the bogies reach certain relative angles on curves, the rotation interpolation flips through the shortest path which happens to be 180 degrees the wrong way.
Things I have already tried:
Separating position (P only, 50/50 Transform) from rotation (R only, Parent constraint targeting front bogie at 100%)
Setting explicit evaluation priorities on all tags
Deleting and recreating the constraint tags fresh
Freeze Transformation on all geometry
The flip persists on Track 03 even with the separated P/R approach.
ISSUE 2 — COUPLER RIGGING
Each coupler connects the rear of one car to the front of the next. The Coupler_CTRL already has a Parent constraint targeting three driver nulls (T1_DRV, T2_DRV, T3_DRV) which is driven by the Xpresso weight system to switch tracks — this must stay.
The problem is getting the coupler to also physically sit between its two bogies and rotate correctly with the track, without conflicting with the existing constraint.
Adding additional Transform and Parent constraints to the Coupler_CTRL causes the couplers to jump to random positions, especially when selected in the Object Manager.
QUESTIONS
What is the most reliable way to prevent 180 degree rotation flipping when using Transform constraints to average rotation between two objects in C4D?
Is there a clean way to stack multiple constraints on the same object without them conflicting — specifically combining an ATS-driven Parent constraint with position/rotation constraints targeting other objects?
Would a different approach entirely work better here — for example using expressions, spring constraints, or a different constraint type?
Happy to share more details, screenshots or the file if helpful. Thanks in advance!
