Hair Plane normals in UE4

Croftyness · May 2015

I've just started to test hair in ue4 however my shader is really uneven. I'm assuming it something to do with the normals as it's fine without one. Does anyone know how I can fix this, or got any suggestions?
I've rendered the normals using a Vray orthographic camera.
Cheers

jfitch · May 2015

I'm not sure what you mean by uneven? What is the issue you're having?

cman2k · May 2015

You haved curved normals baked into your normal map, when you really need something way more neutral. I assume you are re-using these areas of your normal map on multiple cards, but the curvature of those cards isn't consistent, so when it changes you get inaccurate shading.

Are you baking curved pieces of hair onto flat hair cards? Can you get your lowpoly geometry to be closer to your highpoly geometry, before you bake? The closer they are, the less macro-curvature you'll see in your normal map, the more re-usable those modular chunks will be without shading issues.

Croftyness · May 2015

This is my scene set-up. I'm using the Vray Normals render element. How would I go about baking a normal map like you described?

jfitch · May 2015

Ah, okay I see what cman2k is saying. You'll want to bake your normals with the hair straight, not curved or flowing in any way. The curvature and flow will come from the direction of your cards, not your normal map.

Croftyness · May 2015

Thanks for the suggestion. They seem to be ok on alternative flat and curved geometry. I've got some more images that may present the problem better.

Detailed Normal

World Normal

Croftyness · May 2015

The problem is I don't know how to get a tangent spaced bake using Vray.

Veezen · May 2015

I'm not sure exactly how this will affect your hair, but you can try select your hair meshes arranged on head, and under Modifier list choose Edit normals. Click on "[+] Edit normals" and then on "-- Normal". Select all (ctrl + a) and try using three methods:
1) Press "reset" button and check how it looks in UE4
2) Press "unify" button and do the same
3) Move your cursor up, so that the lines which you see (which come from vertices) are straight up.

I remember that I had similar problem, when I import grass meshes to UE4 and I think that I fixed this using one of these method.

leslievdb · May 2015

this might help, create a sphere around your hairmesh and run this script
http://www.scriptspot.com/3ds-max/scripts/normal-thief

what it will do is transfer those sphere normals to the hairmesh and you`ll get nice smoothing

Croftyness · May 2015

Hey thanks for the replies, I tried both of those methods but it didn't seem to work. I think it's a normal map baking problem. In a perfect world I would be able to use render to texture with Vray to get a tangent normal map and the standard complete map. The only work around I can think of is rendering a height map and using a 3rd party tool to convert it.

wes.sau · May 2015

Have you tried rendering the normal with mental ray? Switch to mental ray renderer, assign a standard material to the hair and put a "normals make normal" map type in the self-illumination slot. The normal make normal map can be found in the metaSL section of the available map types. It renders in world space, but rendered from top-down as you're already doing should give tangent-like results.

Croftyness · May 2015

Cool. I'll try that later. I'm using NDO for the time being. It seems to work pretty well if not better.

Hair Plane normals in UE4

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