Baking tearing normals (Both cycles and BI) #43696

New Issue

Andrej Ivanis · 2015-02-16T21:55:57+01:00

Andrej Ivanis commented

2015-02-16 21:55:57 +01:00

There seams to be a bug that normal are teared sometimes this happens with both Cycles (with or without cage) and BI.
Here is the scene setup: bake_bug.blend
This is tangent normal map I got by baking in Cycles with cage, you can see that middle row of bolts is teared sometimes:

I thought there might be a problem with my geometry, but I checked in xNormal it doesn't happen:

There seams to be a bug that normal are teared sometimes this happens with both Cycles (with or without cage) and BI. Here is the scene setup: [bake_bug.blend](https://archive.blender.org/developer/F143853/bake_bug.blend) This is tangent normal map I got by baking in Cycles with cage, you can see that middle row of bolts is teared sometimes: ![bake_2_copy.png](https://archive.blender.org/developer/F143850/bake_2_copy.png) ![bake_2.png](https://archive.blender.org/developer/F143854/bake_2.png) I thought there might be a problem with my geometry, but I checked in xNormal it doesn't happen: ![bla_normals.png](https://archive.blender.org/developer/F143857/bla_normals.png)

Andrej Ivanis commented

2015-02-16 21:55:57 +01:00

Changed status to: 'Open'

Andrej Ivanis commented

2015-02-16 21:55:57 +01:00

Added subscriber: @aivanis

Sergey Sharybin commented

2015-02-17 10:16:58 +01:00

Added subscriber: @Sergey

Julian Eisel commented

2015-02-19 15:31:04 +01:00

Added subscriber: @JulianEisel

Julian Eisel commented

2015-02-19 15:31:04 +01:00

Tried to recreate but getting an error: Error: Uninitialized image "test" from object "fence2_LOD0.008_Circle.009". I'm a noob when it comes to baking, but seems like you didn't pack some images?
Also, could you test if the issue still appears in the latest buildbot builds? Some information about your OS and graphics card might be interesting as well.

Tried to recreate but getting an error: `Error: Uninitialized image "test" from object "fence2_LOD0.008_Circle.009"`. I'm a noob when it comes to baking, but seems like you didn't pack some images? Also, could you test if the issue still appears in the latest buildbot builds? Some information about your OS and graphics card might be interesting as well.

Andrej Ivanis commented

2015-02-19 18:07:43 +01:00

Hi,
I just tested with 2.73.8 version (I downloaded few days ago) and it still appears. Sorry about the error either change image source to generated or here is fixed file bake_bug.blend , just open it and press bake.

OS is Mac OS 10.9.5, graphic card NVIDIA GeForce GT 650M 1024 MB

I get tearing when I bake with either CPU or GPU and also it doesn't appear just on normal map, but on other maps too.

Hi, I just tested with 2.73.8 version (I downloaded few days ago) and it still appears. Sorry about the error either change image source to generated or here is fixed file [bake_bug.blend](https://archive.blender.org/developer/F144852/bake_bug.blend) , just open it and press bake. OS is Mac OS 10.9.5, graphic card NVIDIA GeForce GT 650M 1024 MB I get tearing when I bake with either CPU or GPU and also it doesn't appear just on normal map, but on other maps too.

Julian Eisel commented

2015-02-21 20:15:16 +01:00

Added subscriber: @dfelinto

Julian Eisel commented

2015-02-21 20:15:16 +01:00

Need @dfelinto's brain here! Maybe there's something wrong in the file?

Dalai Felinto commented

2015-02-22 04:41:20 +01:00

Added subscriber: @AndyDavies-3

Dalai Felinto commented

2015-02-22 04:41:20 +01:00

@AndyDavies-3 I haven't tested/checked the file, but if BI has this issue as well I think you could possibly help with other tests (xnormal, ...). Thanks ;)

Andy Davies commented

2015-02-22 05:21:11 +01:00

Interesting. I will take a look tomorrow

marc dion commented

2015-03-12 01:59:34 +01:00

Added subscriber: @MarcClintDion

marc dion commented

2015-03-12 01:59:34 +01:00

From an artists perspective this is easy enough to deal with until a code solution presents itself.

Add some control loops so the geometry is not as long and thin.

To delete the loops afterwards:

(i) Select them all,

(ii) Use 'x' then 'g' to remove them.

Keeping the quads closer to being square shaped also helps to eliminate the oval shaped stretching that can be seen on the end bolts.

You should rebuild the cage since it looks like adding loops can invalidate the cage. Maybe indices are no longer in the proper order?

From an artists perspective this is easy enough to deal with until a code solution presents itself. Add some control loops so the geometry is not as long and thin. ![loops.png](https://archive.blender.org/developer/F149976/loops.png) To delete the loops afterwards: (i) Select them all, (ii) Use 'x' then 'g' to remove them. Keeping the quads closer to being square shaped also helps to eliminate the oval shaped stretching that can be seen on the end bolts. You should rebuild the cage since it looks like adding loops can invalidate the cage. Maybe indices are no longer in the proper order?

Andy Davies commented

2015-03-12 03:58:23 +01:00

Forgot to check this. Sorry!

Marc is correct that adding extra loops can control the projection of the bake, though I must say that tearing is a very unusual symptom as normally the geometry skews when the rays are averaged across the surface.
In addition the centre of an object is usually projected correctly with the ends skewing, so the tearing is quite worrying as is definitely a bug. The tearing doesn't appear in xNormal using unmodified geometry.

I just wanted to point out that while Marc is totally correct about the add/remove loops trick, it should be noted that people shouldn't really be doing it when baking directly to tangent space maps. It's an extremely destructive process and will break your normal map as it encodes data based on the geometry present at the time of the bake and once that geometry is gone it will still try to compensate for it resulting in broken shading.
You can however add extra loops, bake to an object space normal map, remove the loops and then convert back to tangent space without such worries (following Marc's steps)

Forgot to check this. Sorry! Marc is correct that adding extra loops can control the projection of the bake, though I must say that tearing is a very unusual symptom as normally the geometry skews when the rays are averaged across the surface. In addition the centre of an object is usually projected correctly with the ends skewing, so the tearing is quite worrying as is definitely a bug. The tearing doesn't appear in xNormal using unmodified geometry. ![46_Skewing.jpg](https://archive.blender.org/developer/F150003/46_Skewing.jpg) ![xNormal_normals.png](https://archive.blender.org/developer/F149998/xNormal_normals.png) I just wanted to point out that while Marc is totally correct about the add/remove loops trick, it should be noted that people shouldn't really be doing it when baking directly to tangent space maps. It's an extremely destructive process and will break your normal map as it encodes data based on the geometry present at the time of the bake and once that geometry is gone it will still try to compensate for it resulting in broken shading. You can however add extra loops, bake to an object space normal map, remove the loops and then convert back to tangent space without such worries (following Marc's steps)

marc dion commented

2015-03-12 15:57:24 +01:00

Andy makes a good point about baking to Object Space maps first.

Here's more detail on how to prepare a model for texture baking when using Blender's Selected to Active Tool. I posted it to B-Stack Exchange since it's more user-help then debugging. ;)

http://blender.stackexchange.com/questions/27042/how-can-i-bake-textures-without-artifacts-until-the-time-that-the-following-baki/27043#27043

Andy, feel free to comment on any mistakes or omissions I may have made in that post so they can be corrected.

I think it's often better to work with geometry that is made up of proportional, evenly spaced quads just as we'd do for curved animation models in regards to polygon flow.

It seems as if evenly spaced and proportional geometry is able to guide the rays in a way that reduces floating precision errors.

We can see a weird little unit-circle 'math black hole' in action by squaring a series of numbers when their values are greater than 1.0; then comparing the results against what happens when that series of numbers is then squared using their less than 1.0 counterparts. (x > 1.0 versus x < 1.0)

an example:
- 5.0 x 5.0 = 25.0 <-this moves away from 0.0 (and is 5 times larger)

- 0.5 x 0.5 =   0.25 <-this moves towards 0.0  (and is 50% smaller)

(i) Small numbers collapse down to zero when multiplied against other small numbers, the smaller they are, the faster it happens.

(ii) Large numbers can cause the small decimal numbers to become truncated because of floating point round-off which is biased towards preserving the larger numbers. The larger the spread between the high and low values, the worse it gets.

(iii) Multiplying large numbers against small numbers exaggerates the problem further because the very small numbers can quickly collapse the large numbers down to near zero.

If barycentric coordinates are being used to map ray/position hits over to the UV coordinates; long thin triangles may prove to be especially susceptible to floating point round-off errors along one axis more than the other.

I have no idea if that's the case here, and no solid idea how to fix it even if this is part of the problem. :(

Andy makes a good point about baking to Object Space maps first. Here's more detail on how to prepare a model for texture baking when using Blender's Selected to Active Tool. I posted it to B-Stack Exchange since it's more user-help then debugging. ;) http://blender.stackexchange.com/questions/27042/how-can-i-bake-textures-without-artifacts-until-the-time-that-the-following-baki/27043#27043 Andy, feel free to comment on any mistakes or omissions I may have made in that post so they can be corrected. ------ I think it's often better to work with geometry that is made up of proportional, evenly spaced quads just as we'd do for curved animation models in regards to polygon flow. It seems as if evenly spaced and proportional geometry is able to guide the rays in a way that reduces floating precision errors. - We can see a weird little unit-circle 'math black hole' in action by squaring a series of numbers when their values are greater than 1.0; then comparing the results against what happens when that series of numbers is then squared using their less than 1.0 counterparts. (x > 1.0 versus x < 1.0) ------- an example: - 5.0 x 5.0 = 25.0 <-this moves away from 0.0 (and is 5 times larger) - 0.5 x 0.5 = 0.25 <-this moves towards 0.0 (and is 50% smaller) ------- (i) Small numbers collapse down to zero when multiplied against other small numbers, the smaller they are, the faster it happens. (ii) Large numbers can cause the small decimal numbers to become truncated because of floating point round-off which is biased towards preserving the larger numbers. The larger the spread between the high and low values, the worse it gets. (iii) Multiplying large numbers against small numbers exaggerates the problem further because the very small numbers can quickly collapse the large numbers down to near zero. ![unitCircle_float_Trig_precision.png](https://archive.blender.org/developer/F150194/unitCircle_float_Trig_precision.png) ![DSCF1768.png](https://archive.blender.org/developer/F150196/DSCF1768.png) If barycentric coordinates are being used to map ray/position hits over to the UV coordinates; long thin triangles may prove to be especially susceptible to floating point round-off errors along one axis more than the other. ![DSCF1770.png](https://archive.blender.org/developer/F150207/DSCF1770.png) I have no idea if that's the case here, and no solid idea how to fix it even if this is part of the problem. :(

Krzysztof Rećko commented

2015-03-29 00:32:15 +01:00

Added subscriber: @chrisr

Krzysztof Rećko commented

2015-03-29 00:32:15 +01:00

Hey guys, @MarcClintDion was partly right (it's about floating point precision). Took a while to find and fix it though... I hope I've done it right (D1207) :) Any idea who could do review??

Hey guys, @MarcClintDion was partly right (it's about floating point precision). Took a while to find and fix it though... I hope I've done it right ([D1207](https://archive.blender.org/developer/D1207)) :) Any idea who could do review??

blender-admin commented

2015-04-06 07:56:33 +02:00

This issue was referenced by 8cc475c40b

This issue was referenced by 8cc475c40b8e0b316430b536dac7ca0251994124

Campbell Barton commented

2015-04-06 07:58:53 +02:00

Changed status from 'Open' to: 'Resolved'

Campbell Barton closed this issue

2015-04-06 07:58:53 +02:00

Campbell Barton commented

2015-04-06 07:58:53 +02:00

Closed by commit 8cc475c40b.

Closed by commit 8cc475c40b.

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Baking tearing normals (Both cycles and BI) #43696