Field Driver -driving Xpresso via User Data

[williambillcard]

Hi,
I have cloner, cloning Xpresso rigs that drive Tracer objects (think animated Spirographs). The rig has user data to control the wheel size and pen position. I want to use Field drivers and Random Fields to make every cloned rig unique.

I am trying to use a field driver on user data I have set up for my rig. The user data is connected to my Xpresso setup for the rig. This does not seem to work.

It allows me to add the user data into the field driver parameter but the changes to the user data don't seem to affect the Xpresso or objects.

Is this a limitation of Field Drivers?

many thanks in advance!

[Dr. Sassi]

Hi williambilcard.

Please take a look here and share with me what you notice is different.
CV4_2025_drs_25_MGsg_01.c4d
I will have a look into it with more information.

I have used the Linear Field with a wave curve to map data.

Files in the C4D format can be attached here as long as they are smaller than 1MB. If larger, please note that only a few cloud services are used, strictly based on security. (I will share the list and limitations, if needed)

All the best

[williambillcard]

@Dr-Sassi
Hi Dr. Sassi,
Thanks so much for taking a look at this. I can see your example works - but this is driving the user data of the matrix object, not the user data of an object within a cloner.
I attach an example that shows the problem. With the user data cloner if I switch it off the rectangle changes height. If you turn it on the changes stop. it does not seem to make a difference if I move the field driver tag to the cloner object.
user-data-xpresso-cloner_001.c4d

[Dr. Sassi]

Hi williambillcard,

To my knowledge, Cloner-Child based XPresso is calculated before the clone is newly generated. When it is generated, it is not adjusted from the Cloner Child level anymore; any further changes are either Effector/Field-based or on the Field Driver. Placing XPresso between Field Driver and Cloner Child signals that the Field Driver has worked with the XPresso and has no new run again.

The limitation that existed was the reason to have the Field Driver in the first place.

If you could share more about why this feature is important, perhaps we can find a workaround or use the same URL as below and utilize the "Share Your Idea!" option.

Perhaps check with Tech Support, in case I missed something:
https://www.maxon.net/en/support-center

Enjoy your Sunday