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  • Simulating Hair With Imported Hair Xgen Hair

     Michael blaq updated 1 month, 3 weeks ago 3 Members · 7 Posts
  • Kristofer Theorin

    November 28, 2022 at 6:04 pm

    So I’ve exported Xgen hair as an alembic and imported it into Cinema 4D as a hair object. That all looks and works fine, but the way it’s exported bakes every hair down into it’s own hair guide. So that makes simulating the hair subtly bouncing very difficult to do since it’s literally simulating every hair. I was wondering if there was any trick I could use to get around this issue? Since the hair simulation I’m looking for is super subtle and just needs to add enough bounce and back and forth movement to the hair. Is there anyway to maybe bake the hair (while still being able to use the Redshift hair shader on it) and use a mesh deformer to add movement? or some other workaround?

  • Brie Clayton

    December 5, 2022 at 10:42 pm

    Hello Kristofer!

    Is it possible to see your xgen scene and cinema 4d imported scene? Perhaps you could upload a file?

  • Kristofer Theorin

    December 5, 2022 at 11:35 pm

    Sure! Here’s the stripped down C4D file. Unfortunately I don’t the xgen files to reference: https://www.dropbox.com/s/zhcg2n1i9irvzs4/Hair%20Sample.c4d?dl=0

  • Michael blaq

    December 6, 2022 at 12:42 am

    Hi Kristofer,

    I had the chance to review your stripped down scene. I have got a few suggestion to make your scene less heavier and also get some dynamics movement in your scene as how you wanted.

    First of all, hair simulation is based on guides. The guides are simulated and then transferred to the generated hair based on their radius of influence on generated hair.

    With your setup you are importing the cached generated hair to cinema 4d with millions of hair strands which will be difficult for any machine to output a simulated data. On the other hand simulated guides have really low vertex count/point count on each guide strand depending on the hair length.

    Your imported hair has about 99-300 points per hair strands which makes simulation impossible for the total number of hair strands in your scene. Not sure of the current specs of the workstation you are using.

  • Kristofer Theorin

    December 6, 2022 at 12:55 am

    Well luckily C4d does have an option to reduce the amount of points that it simulates with from the guides. So lowering it down to 1 or 2 at least allows me simulate a very slow version of the hair. I just wanted to know if there was some special C4D hair system features that would allow it to be easier. Unfortunately, Xgen hair is imported just as guides (otherwise the shape from Xgen would be lost). So simulation is understandably slow…

  • Michael blaq

    December 6, 2022 at 12:58 am

    My first approach to solving this;
    1. Import guide hair only from maya xgen to cinema 4d.
    2. Simulate the guide hair.
    3. Use the guide hair to generate the dense hair/final hair.
    4. Import groom masks maps (image) to drive the groom layers where necessary. Your scene have four layers of hair groups.
    N.B: Maya uses both ptex and image maps(needs UV’s done) to drive groom mask. Depending on your groom artists workflow.
    5. Bake simulation. (I have shared a sim config preview to achieve the subtle dynamics effect)
    6. Render with redshift

    Second Approach (which you are trying now):
    1. Import the dense hair
    2. reduce the points count per strands by 12-18 based on the hair group and it’s length. Do this under the guides tab on the hair attributes. This will make your scene quite optimized for you to run a simple dynamics sim.
    3. Bake sim and render.

    N.B Make sure your scalp mesh has a hair collider tag for collision of hair strands.

    I hope this helps. Cheers!

  • Michael blaq

    December 6, 2022 at 1:11 am

    C4D doesn’t have a feature to allow you to simulate a dense imported hair scene. with houdini you could sample a percentage of the imported hair as guide and use that to drive the hair sim but not with cinema 4d.

    The best option will be the suggested approach I shared earlier.C4D doesn’t have a feature to allow you to simulate a dense imported hair scene. with houdini you could sample a percentage of the imported hair as guide and use that to drive the hair sim but not with cinema 4d.

    The best option will be the suggested approach I shared earlier.

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