UV: tweak packing heuristics to reduce rotations #112295

Brecht Van Lommel · 2023-09-12T18:32:55+02:00

Brecht Van Lommel commented

2023-09-12 18:32:55 +02:00

UV unwrapping and packing have always done island rotations, but it is happening now in more cases where users prefer it not to. These changes make it less likely that islands will be rotated.

When finding the best packing method, use area as tie breaker

When multiple packing methods result in effectively the same bounds,
prefer the packer that uses the smallest area. When all islands can
easily fit this is usually the box packer instead of alpaca. The zigzag
method of the latter has a tendendcy to take up more area and rotate
islands.

Fix #110724: smart UV project unnecessarily rotates islands

Disable best fit rotation of all islands at end of UV packing

This has a tendency to place islands diagonally in the image which is
not usually wanted, even if it's maximimizing the number of pixels for
the island.

Fix #109906: UV unwrap packs island diagonally instead of straight

UV unwrapping and packing have always done island rotations, but it is happening now in more cases where users prefer it not to. These changes make it less likely that islands will be rotated. #### When finding the best packing method, use area as tie breaker When multiple packing methods result in effectively the same bounds, prefer the packer that uses the smallest area. When all islands can easily fit this is usually the box packer instead of alpaca. The zigzag method of the latter has a tendendcy to take up more area and rotate islands. Fix #110724: smart UV project unnecessarily rotates islands #### Disable best fit rotation of all islands at end of UV packing This has a tendency to place islands diagonally in the image which is not usually wanted, even if it's maximimizing the number of pixels for the island. Fix #109906: UV unwrap packs island diagonally instead of straight

👍 1 ❤️ 1

Brecht Van Lommel added 2 commits 2023-09-12 18:33:07 +02:00

1a26211db4 UV: disable best fit rotation of all islands at end of UV packing

This has a tendency to place islands diagonally in the image which is
not usually wanted, even if it's maximimizing the number of pixels for
the island.

Fix #109906: UV unwrap packs island diagonally instead of straight

buildbot/vexp-code-patch-coordinator Build done. Details

8772523be6 UV: when finding the best packing method, use area as tie breaker

When multiple packing methods results in effectively the same bounds,
prefer the packer that uses the smallest area. When all islands can
easily fit this is usually the box packer instead of alpaca. The zigzag
method of the latter has a tendendcy to take up more area and rotate
islands.

Fix #110724: smart UV project unnecessarily rotates islands

Brecht Van Lommel changed title from ~~UV: tweaking packing heuristics to reduce rotations~~ to UV: tweak packing heuristics to reduce rotations

2023-09-12 18:33:19 +02:00

Brecht Van Lommel requested review from Campbell Barton 2023-09-12 18:33:42 +02:00

Brecht Van Lommel requested review from Chris Blackbourn 2023-09-12 18:33:42 +02:00

Dalai Felinto commented

2023-09-12 20:59:14 +02:00

@blender-bot package

Blender Bot commented

2023-09-12 20:59:17 +02:00

Package build started. Download here when ready.

Package build started. [Download here](https://builder.blender.org/download/patch/PR112295) when ready.

Campbell Barton approved these changes 2023-09-13 01:54:05 +02:00

Campbell Barton commented

2023-09-13 01:57:31 +02:00

Shouldn't the aspect be taken into account? (params.target_aspect_y)
Both these reports use a square image so the difference isn't noticeable.

e.g.

    return (BLI_rctf_size_x(&b) / params.target_aspect_y) * BLI_rctf_size_y(&b) <
           (BLI_rctf_size_x(&a) / params.target_aspect_y) * BLI_rctf_size_y(&a);

Shouldn't the aspect be taken into account? (`params.target_aspect_y`) Both these reports use a square image so the difference isn't noticeable. e.g. ``` return (BLI_rctf_size_x(&b) / params.target_aspect_y) * BLI_rctf_size_y(&b) < (BLI_rctf_size_x(&a) / params.target_aspect_y) * BLI_rctf_size_y(&a); ```

Brecht Van Lommel commented

2023-09-13 02:01:31 +02:00

Dividing both sides by the same factor makes no difference, but I can indeed add it for clarity.

Campbell Barton commented

2023-09-13 02:05:34 +02:00

It's only dividing the width by the aspect though, so unless we know the height is the same, it could make a difference.

Dalai Felinto commented

2023-09-13 11:12:10 +02:00

@blender-bot package

(the build has failed on Windows and MacOS apparently :/ - trying it again for @DanielBystedt )

@blender-bot package (the build has failed on Windows and MacOS apparently :/ - trying it again for @DanielBystedt )

Blender Bot commented

2023-09-13 11:12:13 +02:00

Package build started. Download here when ready.

Package build started. [Download here](https://builder.blender.org/download/patch/PR112295) when ready.

Julien Kaspar commented

2023-09-13 12:39:29 +02:00

I did a bit of testing with various Human Base Meshes and other character files.

When unwrapping a large amount of uv islands the results are the same between this PR and main. Both do a good job in keeping UVs aligned with the object axes.

When unwrapping individual uv islands this PR does a much better job. The unwrapped UVs are consistently well aligned 👍

In this example I unwrapped each UV island individually and packed them afterwards without rotating them. The rotation of UV islands in the PR is typically the same as unwrapping everything at the same time.

main	PR

I did a bit of testing with various [Human Base Meshes](https://www.blender.org/download/demo-files/) and other character files. When unwrapping a large amount of uv islands the results are the same between this PR and main. Both do a good job in keeping UVs aligned with the object axes. ![GEO-body_male_realistic_unwrap_all_pr.png](/attachments/5e286c6a-762e-4ce8-9ca0-a8f121b6b1e7) When unwrapping individual uv islands this PR does a much better job. The unwrapped UVs are consistently well aligned 👍 In this example I unwrapped each UV island individually and packed them afterwards without rotating them. The rotation of UV islands in the PR is typically the same as unwrapping everything at the same time. | main | PR | | -------- | -------- | | ![GEO-body_male_realistic_unwrap_individual_main.png](/attachments/e7c9f046-f3e5-4061-8bd9-7de908a6ae00) | ![GEO-body_male_realistic_unwrap_individual_pr.png](/attachments/b0d8da77-85c2-49f7-becf-cf73ba6fa14a) |

GEO-body_male_realistic_unwrap_all_pr.png

1.6 MiB

GEO-body_male_realistic_unwrap_individual_pr.png

1.6 MiB

GEO-body_male_realistic_unwrap_individual_main.png

1.9 MiB

Brecht Van Lommel referenced this issue from a commit

2023-09-14 19:05:13 +02:00

UV: disable best fit rotation of all islands at end of UV packing

Brecht Van Lommel referenced this issue from a commit

2023-09-14 19:05:16 +02:00

UV: when finding the best packing method, use area as tie breaker