My team is looking to use the hair shading model with a non-groom asset.
We are creating the cards ourselves and baking the various textures, such as the tangent.
We are finding that we are not able to get the desired results and would like to confirm the format and requirements of the tangent used by the hair shading model.
Initial investigation has confirmed that it is not the same as the general anisotropy as used by the the default shading model.
It does not use the World Tangent.
Alters the world normal.
Also appears to impact the subsurface colour.
I have been unable to find any documentation about what the correct formatting for this tangent.
It would also be useful to know if there was any way to integrate the infomation that would usually be found in a normal map, for greater strand definition.
When using the Hair shading model within a material, the Tangent input can be provided. By default the local tangent orientation should be on the green channel to follow the strands tangent. I attached an example of a beard mesh with the visualization of the tangent orientation to visualize the flow better.
[Image Removed]By default the tangent are expressed in local tangent space:
green: strands direction,
red: perpendicular to the strands directions but in the card plane
blue: perpendicular to the strands directions but perpendicular the card plane (~normal)
[Image Removed]
You can enable the same visualization by adding a groom asset in your scene and then using the Lit>Groom>Tangent visualization mode. It will show the tangent orientation on any hair material.
Thanks for getting back to me. That info is useful.
I notice that the example/info there is using groom. We are not using groom, is there anything different when working without groom that I should know?
Does the mesh require any particular setup? or the tangents require any space conversion?
I will follow up tomorrow with more info/questions. It’s EOD here and I just fire that clarification out today.
The plane mesh and beard are not using groom. They are simple static meshes. I only mentioned that, adding a groom (it could be anything, independent of your card mesh) in the scene, is necessary if you want to display the tangent direction as I did above.
The information above has been very helpful and answered most of my questions.
I haven’t had a chance to follow up my end fully, I will be out of office for a few days and would ask you not to close this thread just yet, will get back to you shortly.