Symmetry issue involving normal maps

[natetheartist]

[semi-resolved]

Long time no post. Anyway-

I'm having a very annoying issue in UDK. Wherever I have symmetry, my normals get EFF'd up.

My UV's are separated and overlayed exactly.
It looks like its actually reading the green/z (?) channel as it's inverse on one side.

If someone could explain how to fix this, I'd be very appreciative.

example:

http://img375.imageshack.us/img375/6728/symmetryerror.jpg

[kdm3d]

Change your compression to on your normal map to TC_Normalmap_uncompressed... that shouldn't be necessary, but I found it to be in some cases...

[natetheartist]

Change your compression to on your normal map to TC_Normalmap_uncompressed... that shouldn't be necessary, but I found it to be in some cases...

I tried that, but as expected, it didn't have any effect.
I'm pretty sure this doesn't have anything to do with the compression, It has to do with the symmetry and possibly a channel of the normal that is getting flipped due to symmetry.
Thanks for tryin though :/

[moose]

where is your UV seam? are you mirroring vertically or horizontally?

[natetheartist]

where is your UV seam? are you mirroring vertically or horizontally?


please excuse my shitty mouse outlines:

here's an image of the uvs and where that particular image (above) is symmed

http://img830.imageshack.us/img830/6728/symmetryerror.jpg

Keep in mind though, that this happens wherever I symmetry anything with normals....so either its a global issue, or there's something I don't know about how to symmetry for udk.

[Mark Dygert]

What does the normal map look like when its applied in max?

Are you baking with both halves in the 0-1 space? If so offset one of the pieces one tile to the right, left, top or bottom so it falls outside the 0-1 rendering space but still lands on the exact spot it should one tile over.

It could be that you need to weld or unweld your UV seams before baking.

[natetheartist]

What does the normal map look like when its applied in max?

Are you baking with both halves in the 0-1 space? If so offset one of the pieces one tile to the right, left, top or bottom so it falls outside the 0-1 rendering space but still lands on the exact spot it should one tile over.

It could be that you need to weld or unweld your UV seams before baking.


Vig, long time.

No, the Symmed area is outside of the 0-1 space, Placed on the same uv coordinates as the piece that IS in the 0-1, but outside, -1 on U. However the seam lines up (in tilespace).
If you look at the first image posted, you can see that the problem isn't with the alignment, The problem is that for some reason the flipped UVs recieve lighting inverted lighting information on one channel.

This is bugging the hell out of me.

As you can see, it looks fine when rendered in MAX

http://img828.imageshack.us/img828/6728/symmetryerror.jpg

[natetheartist]

I found this thread:
http://www.polycount.com/forum/showthread.php?t=51088

Unfortunately, I believe I have a different issue. As you can see in the first post, its not a matter of a seam as much as a channel/lighting issue on one side of the symmetry.
I keep reading vague whispers of an inverse-lighting-across-mirrored-geometry problem....maybe that's it??? Any ideas???

[jacob07777]

Same thing happened with my Modeling and Architecture building. Just be sure when you're exporting the file in Max that it's the full object and you're not mirroring it in the editor. Then in Max just like reset xforms, so on and so forth

[kdm3d]

DONT do that tutorial for fixing seams...... theres no reason to if your baking correctly.

I had the same problem in UDK, and like I said, I fixed it by changing the normal map compression. Have you tried each setting of compression? Double check thats not the problem.

[natetheartist]

Same thing happened with my Modeling and Architecture building. Just be sure when you're exporting the file in Max that it's the full object and you're not mirroring it in the editor. Then in Max just like reset xforms, so on and so forth

The model is being exported as a whole. No geometric mirroring is being handled in UDK.

I spoke with Carlos at HighMoon, and he theorizes that UDK have an issue with horizontal symmetry, suggesting that I try rotating my uvs 90 degrees so that the symmetry is vertical (symmed across x instead of y). I'll try this when I get out of work and post the results.

I'm surprised that this hasn't been addressed anywhere (that i've seen). This has happened every time i try cross-planar symmetry. (same thing happened with my art-deco scene, jake.)

[Digital Dino]

Are you literally using symmetry? As in the modifier
Have you tried cloning a side and mirroring it instead?
I have quite a few models in UDK right now that I've cloned, mirrored, and welded down the center and I can't say that I've had that issue with the normals

[Fallen Prophet]

Did you collapse the mesh in Max before exporting to UDK? I'm not sure if it will help or not, but I've never seen that particular problem before.

If you can't find a better solution, a cheap workaround would be to go back into Max, select the polygons on the side that is getting distorted, flip their normal direction, and re-export the mesh. It's not an explanation as to what is causing the problem but it should fix it.

[chadabees]

I believe that when you use symmetry for UDK you have to have the UV's setup to mirror left/right not top/bottom.

[natetheartist]

I believe that when you use symmetry for UDK you have to have the UV's setup to mirror left/right not top/bottom.

I'll test this asap.

In the meantime, can you explain why this is? You're the second person to suggest that. I'd love to understand the route of the problem.

[P442]

turn on backface cull on your model in max and make sure those faces aren't flipped

[chadabees]

I believe that when you use symmetry for UDK you have to have the UV's setup to mirror left/right not top/bottom.

To be honest I didn't have a clue why but I did have a forum post bookmarked from the epic forums where someone said, "this is due the way the shadow maps (not the lightmaps) are encoded with the normal maps. Because the shadow maps are used for static lighting, these artifacts will be merely visible or won't be visible at all when using the realtime lighting. You won't see it in maya or other 3d application either becuase they don't use shadow maps - at least not in the same way like UE does."

http://forums.epicgames.com/showthread.php?t=665046

Not sure if this is the correct reason or not.

[Ben Apuna]

Info about mirroring straight from the source:

http://udn.epicgames.com/Three/LightMapUnwrapping.html

A recent thread about it.

http://www.polycount.com/forum/showthread.php?t=75993

Basically make sure to mirror your UVs so the seam is vertical up/down not horizontal left/right. But keep in mind that at best it will only reduce the problem and not completely eliminate it.

Lightmap UVs and baking lights will also play a huge role in how bad the seams are.

[natetheartist]

I tried everything.

When looking at the mesh in the mesh editor window, a combination of the 128 color blend fix and the tc_uncompressednormalmap helped. In fact, it solved the problem *in the mesh editor*.

Unfortunately, the second i ran a build, the problem was as bad an apparent as ever.

I also tried several different things with my lightmap. Including increasing its resolution all the way to 512.

I also tried turning the UV's so that the mirroring was horizontal instead of vertical to no avail.

I'm *SO* depressed that I can't figure this out. This seems like a really apparent issue. I'm surprised it hasn't been addressed in any of the many recent UDK builds.

I've spent too long and gotten too stressed about this. I think I'm going to give up and just move on for now. If no one (including me) can figure out a way around this within the next few days, I'll probably just give in and spend the texture space to not use symmetry on anything planar. ....seems sooo wasteful

http://img59.imageshack.us/img59/6343/halpx.jpg

[Ben Apuna]

Don't trust anything you see in the static mesh viewer unless you only plan to use dynamic lighting, because that's what it's showing you.

1. Rotate those sections 90° in the primary UV set, don't forget to re-bake the normal map or use these Normal Map Actions for Photoshop (http://www.sinistergfx.com/data/ps/sgfx_normal_map_actions.zip) by Will "sinistergfx" Fuller (http://www.sinistergfx.com/) for quick normal map 90° rotating.

2. Redo your lightmap UVs (see this tutorial (http://stephenjameson.com/tutorials/lightmap-uvs-tutorial/) written for UT3, everything is still valid except you don't need padding around the outer edge of 0-1 UV space anymore)

Currently they are packed way too close together, you need at least 4 lightmap pixels in between each UV shell otherwise light from the different shells will bleed onto each other.

Merge those two shells together so there isn't a seam. Any seams in the lightmap UVs will result in a visual seam after building lighting.

3. Then change the Indirect Normal Influence Boost setting from 0.3 to 0.

View -> World Properties -> Lightmass -> Lightmass Settings -> Indirect Normal Influence Boost

4. Finally rebuild your lighting.

Following those steps should result in a less visible seam.

I hope that helps.

[natetheartist]

Don't trust anything you see in the static mesh viewer unless you only plan to use dynamic lighting, because that's what it's showing you......

....Following those steps should result in a less visible seam.

I hope that helps.

I was about to give up, and yet,
here you are....
...rocking like a hurricane....


I'll give this a shot once i've mopped up the tears and pulled hair from my keyboard.
Thanks in advance.

[Ben Apuna]

That's cool, don't give up.

But remember before you invest more blood sweat and tears, this won't eliminate the seam 100%, it'll only make it less visible.

If you really need it 100% seamless then you'd best not mirror that section. At least for this model it's not that huge a piece so you won't lose that much texture res by making it unique.

On the other hand sometimes it's possible to get away with a seam. Once an object is fully textured and lit it becomes less visible. As long as you aren't planning to texture it in a pristine shiny state.

Definitely at least rotate those UVs though, even if you decide to live with the seam. Mirroring in the other direction should yield a better result.

Well best of luck with this thing. I personally think this is one of the most frustrating aspects of making art assets for Unreal.

[natetheartist]

That's cool, don't give up.
...I personally think this is one of the most frustrating aspects of making art assets for Unreal...


Currently redoing my lightmaps. Looks like that link you left is broken. Could you relink me?

[natetheartist]

Is this spacing better for the lightmap?

Also, what resolution lightmap do you recommend for an asset that is around 128x128x32 Unreal Units?
http://img821.imageshack.us/img821/5338/halpf.jpg

[natetheartist]

New results:

much improved. Looks like the lightmap is getting pretty cruddy looking, but I'm sure some diffuse and spec will help that a lot.
lighting should help too, I'm sure.

http://img202.imageshack.us/img202/990/halpjn.jpg

[Ben Apuna]

It's looking better, I think that's just about as good a result as you will get on that front panel while still mirroring it.

That link works for me strange... well here it is in long form:

http://stephenjameson.com/tutorials/lightmap-uvs-tutorial/

http://stephenjameson.com/tutorials/lightmap-uvs-tutorial/

Hopefully that works for you.

About your lightmap UVs. Depending on the resolution you are setting for you lightmap, they're still too close together in some parts. I think for that size of an object not more than 64x64 pixels, but it kind of depends also on how big your scene will be. The more objects the more lightmaps get made which means more memory needed to store the lightmaps.

Also you don't need that padding around the outer edge of 0-1 UV space for lighmap UVs. You only need the padding between the different shells.

For a portfolio piece I think it's totally acceptable to crank up the quality so it just "looks good", just don't go too far overboard giving everything a 2048 or 4096! lightmap even a 1024 is kind of nuts unless it's for a huge object. I've found UDK/Lightmass to be pretty good at preserving shadow details even at lower resolutions than you might think.

It's perfectly fine to stretch and twist lightmap UV shells into nice rectangles and squares so that they can get packed closer together without wasting precious texture space. When you're using a 32x32 or 64x64 every pixel counts...

Try to merge as many lightmap shells as you can so you don't need as much space devoted to padding. Though you need to watch out, taking this too far can result in an undefined blobby mess. But for organic objects this is the ideal approach.

Sometimes you can just planar unwrap a side of an object and it'll work out great as long as nothing protrudes too far in or out. If that happens just break the offending UVs off and make them a separate shell.

I wish UDK supported non-square lightmap resolutions, but oh well...

[moose]

i asked about the UV mirroring because the orientation does matter. Turn those puppies 180 degrees! mirroring on V will cause that seam. Mirror on U! It is due to how lightmaps work. While all the stuff you have done so far is definitely good (lightmaps, etc), try mirroring across U instead of V.

[Papa_Austin]

hey Nate with that little bit of seam you have left, why not just apply a detail normal? it will also help hide the seam even more

[Pope Adam]

Gotta bump this thread... I'm having a very similar issue...

Strange thing is... mine was working just fine for about 3 months, when all of a sudden, these shading errors start showing up and I can't figure out how to get back to how it was before... Here's my screenie.

http://dl.dropbox.com/u/29303569/NGHS/Progress_Shots/issues_001.jpg

[Xendance]

Try clearing the swarm cache. You can do that in the application that fires up when you build lighting.

[Pope Adam]

I got a fix - copy/paste from my other thread where i was investigating the problem:

no light maps at all yet... and the lighting is unbaked...

howeveR!! i found a solution - I found what went wrong... in my normal map texture, the "unpack min" settings had gotten set to 0 0 0 instead of -1 -1 -1 somehow...

totally screwed me over for like 3 hours tonight - and now i feel dumb for posting this. Anyway, if this happens to anyone else, after you've exhausted all the other threads on this issue, check your unpack min and unpack max numbers in the texture viewer inside the content browser.

cheers - adm