How do I keep hairs from passing through objects?

[cyrilrueg]

I've applied the Hair Collider tag to the face object, but when I apply a simulation of the hair strands, they pass through the face.

[Dr. Sassi]

Hi cyrilrueg,

Sorry for the delay, but my day was completely disrupted by an extended power outage after the transformer exploded on the other street side with a big buzz sound and a blue flash brighter than the sunlight here.

I assume that Hair> Dynamic> Collision is enabled.

If you have a small scene, please share it. (If it is larger, as usual, I only open Dropbox, Apple, Adobe, Google, and Wetransfer files.

To exclude technical limitations, please look at the file below in the area inside the torus frame. Start at frame zero and let it play to frame 36 or so. Then render.
CV4_2024_drs_24_SIhc_01.c4d

There are Guides and Hairs.

Guides explore the topography, and Hairs are then interpolated. In other words, most hairs have no idea about their context. (Well, you can switch to individual Hair in the Dynamics tab of the Hair object, but that might create a huge calculation time.) Like most simulations, it tries to get away with the least amount of effort to keep things responsive.

Could that be the problem (interpolation)? I typically relax Hair, set the initial state, (style it) and then put the Hair dynamic to rigid. (Rest/Hold state…)
https://help.maxon.net/c4d/2024/en-us/Default.htm#html/OHAIR-HAIRSTYLE_GROUP_DYNAMICS.html#HAIRSTYLE_DYNAMICS_APPLY

If that does not help, we can take a deeper look. Substeps and iteration might help if they are increased.
The Surface Radius in the Dynamic settings might help.

Each scene is different, going by the character's motion, the setting, and Segments, etc.

All the best

[cyrilrueg]

Hello @Dr-Sassi , and thank you very much for your reply. Wow that sounded impressive! Hope you're ok.
Do you mind watching the scene quickly? I've reduced the elements to essentials.
https://we.tl/t-ilwG23gxHD

[Dr. Sassi]

Hi cyrilrueg,

Yes, thank you. Everything is fine. We called, and the new gear was installed the same day. Even they were blown around in their Cherry-Picker repairing this stuff.

Thanks for the file; always so much better. Thank you as well for using Wetransfer.

Please check out the manual about Parting, which was pretty much my question from above.
https://help.maxon.net/c4d/2024/en-us/Default.htm#html/OHAIR-HAIRSTYLE_GROUP_PARTINGS.html#HAIRSTYLE_PARTINGS_INCLUDE

Guides typically explore the model and then interpolate the Hair. Setting hairs to Dynamic (instead of guides) will significantly slow down the process.

To have 100 segments in Hair might be overkill.

One aspect might be necessary: Material settings like Clump will set things independent from Dynamic. See image.

If things do seem not to work as I like to, I start in a new scene with a super simple setup. This often helps to find the "missed" parameter - perhaps adjusted before and forgotten.

Enjoy your project, and have a great Sunday!

[cyrilrueg]

Hi @Dr-Sassi , thanks for these explanations! Hair is really challenging for me! I hope there will be a Youtube Demystification about it

Best
Cyril

[Dr. Sassi]

Hi Cyril, you're very welcome.

Even Hair is easy to set up, it can go relatively deep, and yes, the application is mostly parameter-driven when one excludes the Styling tools. In other words, the number of parameters and tabs doesn't support a lot of intuitive handling; what is possible needs to be known. The content mentioned below puts a great deal of light on that subject.

There are two series over at the old Cineversity
https://www.cineversity.com/vidplaytut/hair_overview_the_hair_menu_-_part_1

Sadly, two detailed series are available with an older GUI, but the functionality hasn't changed.

• The Hair Menu
• Everything Hair

There was a DPP episode about Hair:
https://www.youtube.com/watch?v=KiElJ-ssIqg

I hope that helps.

My best wishes