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# Objective Models can be produced that do not have vertex tangents but do have normal map textures. The tangents can be generated. There is a way that the vertex tangents can be generated to be exactly invertible to avoid introducing error when recreating the normals in the fragment shader. ## Solution - After attempts to get https://github.com/gltf-rs/mikktspace to integrate simple glam changes and version bumps, and releases of that crate taking weeks / not being made (no offense intended to the authors/maintainers, bevy just has its own timelines and needs to take care of) it was decided to fork that repository. The following steps were taken: - mikktspace was forked to https://github.com/bevyengine/mikktspace in order to preserve the repository's history in case the original is ever taken down - The README in that repo was edited to add a note stating from where the repository was forked and explaining why - The repo was locked for changes as its only purpose is historical - The repo was integrated into the bevy repo using `git subtree add --prefix crates/bevy_mikktspace git@github.com:bevyengine/mikktspace.git master` - In `bevy_mikktspace`: - The travis configuration was removed - `cargo fmt` was run - The `Cargo.toml` was conformed to bevy's (just adding bevy to the keywords, changing the homepage and repository, changing the version to 0.7.0-dev - importantly the license is exactly the same) - Remove the features, remove `nalgebra` entirely, only use `glam`, suppress clippy. - This was necessary because our CI runs clippy with `--all-features` and the `nalgebra` and `glam` features are mutually exclusive, plus I don't want to modify this highly numerically-sensitive code just to appease clippy and diverge even more from upstream. - Rebase https://github.com/bevyengine/bevy/pull/1795 - @jakobhellermann said it was fine to copy and paste but it ended up being almost exactly the same with just a couple of adjustments when validating correctness so I decided to actually rebase it and then build on top of it. - Use the exact same fragment shader code to ensure correct normal mapping. - Tested with both https://github.com/KhronosGroup/glTF-Sample-Models/tree/master/2.0/NormalTangentMirrorTest which has vertex tangents and https://github.com/KhronosGroup/glTF-Sample-Models/tree/master/2.0/NormalTangentTest which requires vertex tangent generation Co-authored-by: alteous <alteous@outlook.com>
35 lines
1.5 KiB
Markdown
35 lines
1.5 KiB
Markdown
# bevy_mikktspace
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This is a fork of [https://github.com/gltf-rs/mikktspace](https://github.com/gltf-rs/mikktspace), which in turn is a port of the Mikkelsen Tangent Space Algorithm reference implementation to Rust. It has been forked for use in the bevy game engine to be able to update maths crate dependencies in lock-step with bevy releases. It is vendored in the bevy repository itself as [crates/bevy_mikktspace](https://github.com/bevyengine/bevy/tree/main/crates/bevy_mikktspace).
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Port of the [Mikkelsen Tangent Space Algorithm](https://en.blender.org/index.php/Dev:Shading/Tangent_Space_Normal_Maps) reference implementation.
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Requires at least Rust 1.52.1.
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## Examples
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### generate
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Demonstrates generating tangents for a cube with 4 triangular faces per side.
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```sh
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cargo run --example generate
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```
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## License agreement
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Licensed under either of
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* Apache License, Version 2.0
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([LICENSE-APACHE](LICENSE-APACHE) or [http://www.apache.org/licenses/LICENSE-2.0](http://www.apache.org/licenses/LICENSE-2.0))
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* MIT license
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([LICENSE-MIT](LICENSE-MIT) or [http://opensource.org/licenses/MIT](http://opensource.org/licenses/MIT))
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at your option. AND parts of the code are licensed under:
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* Zlib license
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[https://opensource.org/licenses/Zlib](https://opensource.org/licenses/Zlib)
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Unless you explicitly state otherwise, any contribution intentionally submitted
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for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
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dual licensed as above, without any additional terms or conditions.
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