Issue with hair render : Redshift hair doesn't match the C4D standard render !

[load-traffic]

I need some help please !

So I added hair to a mesh and controlled its length curls twist ... in the standart c4d hair material and for the color and spec i used Redshift and then arnold standard hair . However when i render in redshift or arnold i dont ge the result i want . The main problem comes from the lengh parametre in the native hair material . Somehow arnold and redshift does not work well with it . Because when i disable it the hair kinda render properly but i dont get the length falloff i'm aiming for .

I just want the same result i get in the standard render to be in the redshift and arnold render !

I hope it makes sense !
login-to-view

Higher quality image ; (https://ibb.co/9nfqG8W)

[Dr. Sassi]

Hi load-traffic,

I have no file from you, so it is difficult to tell what your setup is and what happens.

I placed hair on an object, curled it, then changed the length. (Each time, I cached it to get started from the same base.)

Perhaps this helps
https://youtu.be/KiElJ-ssIqg?feature=shared&t=3190

For any Arnold questions, please check in with the resources Arnold offers; I don't have a license nor any reasonable knowledge about it. (Last training with Arnold was around ten years ago, so that is a no-go.)

Since you say Redshift 3D and Arnold have the same result, I think the images below, rendered in Standard (on the left) or Redshift 3D (on the right), should help. The light is different, hence the brightness and saturation.

login-to-view
login-to-view

I'm happy to have a look at your file. Either here as a c4d file (below 1MB, just the needed parts) or as cloud share (I touch only Dropbox, Wetransfer, Google, Adobe, and Apple as cloud services; thanks for understanding)

All the best

[load-traffic]

Hello Dr. Sassi !
thank you for the reply !
here is the file : https://we.tl/t-5kLTWT7UQ9

[Dr. Sassi]

Hi load-traffic,

Thanks for the file and for using Wetransfer; it is very kind of you.

Something is off with the file, but I think that would be a case for the tech support, as I can reproduce it in a new file.

My suggestion is that we check step by step what works on your side.
https://stcineversityprod02.blob.core.windows.net/$web/Cineversity_Forum_Support/2023_PROJECTS_DRS/20231230_CV4_2024_drs_23_HArs_02.c4d.zip

login-to-view
Here is a file that is newly set up based on your wing object. Render it in Standard and Redshift. I get the same result in terms of hair shape.
When I get your results, we can take it from there.

Have a great weekend.

[Dr. Sassi]

P.S. I found it.

The UV polygons were sitting X=+1.0.
When moved to X=-1.0, they sit inside the 0-1 UV space. The hair system works for Redshift.
https://stcineversityprod02.blob.core.windows.net/$web/Cineversity_Forum_Support/2023_PROJECTS_DRS/20231230_CV4_2024_drs_23_HArs_11.c4d.zip

login-to-view

Place the project file in your project folder so the texture ("hair mask o1.png") is found.

Cheers

[load-traffic]

Thank you Dr. Sassi !
I cannot thank you enough .
I really I appreciate your time .

[Dr. Sassi]

You're very welcome, load-traffic.

It is very nice of you to take the time to reply.

My best wishes for 2024.