Need help with Normal map issue

Trevor · Jan 2015

Ive been working on a dagger and I cant get the edge of this blade to bake right. The blade is mirrored with smoothing splits for each uv island.
Could it be my topology on the high poly? if so what is the best way to model a blades edge for a clean bake?

Help would be met with many songs of appreciation.

Problem (circled in red)

Additional info

High poly

High poly cage (zoomed in to problem area)

Normal map

Marshkin · Jan 2015

It could be the angle on your high poly is too sharp? (this is a wild guess since baking normals still gives me sass on a regular basis)

Can we see your low poly mesh and your UV layout?

AdvisableRobin · Jan 2015

When you are baking the normal map, are the mirrored UVs overlapping or did you offset them out of the 0 to 1 space?

Quack! · Jan 2015

You should have at least 8px of padding on your uv island normal map edges at this resolution. Not having that can cause artifacting.

marks · Jan 2015

Quack! wrote: »

You should have at least 8px of padding on your uv island normal map edges at this resolution. Not having that can cause artifacting.

You can never have enough padding. I set mine to like 9999px whenever I bake anything.

Trevor · Jan 2015

Mirrored uvs are all offset out of 0-1 space.
Cranked padding up to 20, no help. That green border is still there.

Here is the Low poly over the high poly (top) and just the low poly (bottom

UVs

EarthQuake · Jan 2015

What are you rendering in? I've seen similar issues with Maya shaders that had nothing to do with the art content itself.

Trevor · Jan 2015

Rendering in 3ds max

Edit: AA set to Mitchell and supersampling set to Hammersley

AdvisableRobin · Jan 2015

Couldn't it be because the lowpoly's blade portion doesn't have the same thickness that the highpoly does?

JedTheKrampus · Jan 2015

I'd put my money on it being a problem with the 3ds Max tangent basis. Try rendering the normal map in Xnormal (make sure you have export tangents and binormals unchecked on your lowpoly model, and that smoothing groups are exported on your lowpoly) and rendering the knife itself in Toolbag with tangent space set to Mikk, or Blender or UE4. (For UE4 you'll need to change the tangent space swizzle from X+Y+Z+ to X+Y-Z+ in Xnormal of course.)

Trevor · Jan 2015

I dont think its the tangent basis. Just did a bake in Xnormal, got the exact same results.

sushi · Jan 2015

if you can afford it, try adding more geometry

EarthQuake · Jan 2015

Try loading this into Marmoset TB2, grab the demo if you don't have a copy. I'm almost entirely convinced this is a shader problem and not actually anything wrong with your content. Feel free to package the model/nm up and I'll look at it myself too.

rollin · Jan 2015

edit: no no no.. not right
edit2: ok new guess.. the lp is catching the edge of the hp. this would cause the green border. padding wont make it go away. Together with the shader bleeding these green pixel into the blade would cause such an edge. Just as test.. what happens if you paint away this green/blue edge and what happens if you make the lp-knife-edge a bit shorter then the hp so that it does not catch the rounding

Trevor · Jan 2015

@Earthquake: The very first image with the problem area circled in red is a TB2 render. I would be happy to package it up for download, It would be my first time doing such a thing. what site would you recommend for the download?

@Rollin: Made the LP knife edge shorter, didnt work and gave me some other very slight artifacts. Painting it away worked BUT isnt the whole concept of this to NOT paint away errors on normal maps since each pixel is a stored vector?

rollin · Jan 2015

Yes theoretically it is not correct but what you are doing is to make the lowpoly look like the highpoly.. but it is NOT the highpoly.. so there must be something wrong about the lowpoly + nm.

Your problem demonstrates one of these cases. What you see is a correctly baked normal projection but your mind tells you "no no, the edge of the blade can't look like that". Both, the bake and your mind are correct

I'm sure you can build the lowpoly in a way or use a cage to directly bake correct.. But that's nothing else as just making the projection a bit more correct.
Painting over it is just the faster way and a bit hacky but imo everything is allowed what gets the job done

edit: just as an additional note: how big do you like the pixel to be which is storing the cutting-edge normal facing in the cut direction of a sharp blade?

EarthQuake · Jan 2015

Dropbox should work. If you include the high and can try rebaking it as well.

Trevor · Jan 2015

Here is the link to everything used for the bake including the resulting normal map from Xnormal. Thanks Earthquake!

https://www.dropbox.com/sh/58nauexstfzfc4m/AADLB21Fa2zPt_fJZQxyfDO0a?dl=0

rollin wrote: »

edit: just as an additional note: how big do you like the pixel to be which is storing the cutting-edge normal facing in the cut direction of a sharp blade?

Im afraid I dont quite understand the question. Aren't the pixel sizes all the same in this case?

rollin · Jan 2015

was just joking. Point is, even one pixel of a 4k map would be too big to represent the blade edge normal. So you loose nothing. It's more of a workflow problem if you paint in your normal map. If you just do it for you and nobody else is working on it's up to you. In a professional workflow it would be good if you could setup your hp and lp to bake without this green edge.

EarthQuake · Jan 2015

Just took a quick look here and haven't tried to rebake, but it looks like your normal map doesn't have any edge padding. Try to re-bake it with edge padding and see if that helps.

Trevor · Jan 2015

Edge padding didnt help, tried that a couple of times.

rollin · Jan 2015

I took a look. Check how the edge of the high an lowpoly match up. How should this bake without a border?

make the hp as sharp as the low (as far as possible) and match the middle line. You have an offset to the right if you look in the direction from the grip to the blade.

Also you have offseted the uv shell which is a bit better aligned to the hp.
So you are baking from the less good side.

Make this clean and you get a better result. Maybe loosing most of the border. A bit waviness will stay if you don't put more polys into the rounding of the blade edge.

Trevor · Jan 2015

That worked!

Correct

Thank you all so much. This problem was really getting under my skin.

Need help with Normal map issue

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