Dynamic Follow Attract
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Hi again,
Quick question, I'm trying to make a sphere roll around a scene and dynamically interact with objects on the floor.
I first tried using Follow Position and Rotation in the Rigid body tag of the sphere and have it align to spline, but it doesnt roll very well noor does it interact with objects on the floor very well.
So I thought using a Field Force to attract the sphere to a moving object might work better - and it kinda does, however it slips and slides a bit (despite huge Friction values) and it goes though the objects constantly, and just doesnt look very realistic at all.
Here's my project file, is there a better way to set this up, or have I missed a setting in the field force somewhere? https://we.tl/t-UYwXxNVbh9
Thanks again!
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Hi MaverickMongoose,
Thanks for the file.
I'm not aware if you have tried this. Throwing a hula-hoop ring away from you, while at the same time setting the ring in rotation that would go against the forward movement. At one point, the rotation has canceled the forward motion, and the ring comes back. In short, two forces fight against each other; if they don't cancel each other out, one or the other wins.
The same feeling is present in the large Sphere; the Rotational Mass is set to 100%. If set to 1%, the Sphere can roll more smoothly along its path, with no heavy inertia fighting against the rotation.
The example below replaces the Force and uses a Spring instead, which allows the larger Sphere to exhibit more of its inherent energy and define its own path more effectively. While the Rotational mass is 1%, which allows quickly to adapt.
Enjoy
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Ooh thats an intresting setup too, thanks for that!
Just one thing though, if you look from the side in your and mine the sphere doesnt interact with the collider objects very well, often going through or floating above. Any idea why that is?
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Thanks for the feedback, MaverickMongoose,
Please explore the Rigid Body Tag > Collision > Search Radius. Increase to perhaps 5cm, then adjust to a lower or higher setting.
https://help.maxon.net/c4d/2026/en-us/Default.htm#html/TRIGIDBODY-RIGIDBODY_PBD_COLLISION_GROUP.html#RIGIDBODY_PBD_THICKNESS
Let me know if that works for you.
All the best
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All good, turns out Set Absolute Velocity messes up the gravity, switched to Add to Velocity and increased the substeps and it's working good now - changing the object mass helped too, thanks for that!
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Thanks for the reply, MaverickMongoose.
You may also explore the Attribute Manager> Mode> Scene> Simulation> Simulation> Steps.
Think of a sphere on your table, a real metal sphere, and a real table, how often would you estimate the sphere tests if the table provides resistance to go through? [∞?]
Since we most likely do not have a supercomputer farm running our simulation, the forces an object has to collide with another are tested a few times, but surely not infinitely. So when the motion of an object is fast, it might test for no collision, but when the next test happens, it is already beyond the collision point. Well, that is also not that simple, as a sphere collides with points above the collision surface halfway through. Therefore, the sampling or steps need to be higher to prevent this from happening, as it can become stuck partially inside an object.
If there is a high velocity, it appears to be messing with gravity, but it is reaching only a speed that is too fast for the steps to be successful in determining a collision. The search radius is a helpful feature, providing an early warning (simplified).
I avoid mentioning the substep option early, as it changes the course of the outcome.
Cheers
