bdef86ea6e
# 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>
86 lines
2.7 KiB
Rust
86 lines
2.7 KiB
Rust
#![allow(clippy::all)]
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use glam::{Vec2, Vec3};
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mod generated;
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/// The interface by which mikktspace interacts with your geometry.
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pub trait Geometry {
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/// Returns the number of faces.
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fn num_faces(&self) -> usize;
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/// Returns the number of vertices of a face.
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fn num_vertices_of_face(&self, face: usize) -> usize;
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/// Returns the position of a vertex.
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fn position(&self, face: usize, vert: usize) -> [f32; 3];
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/// Returns the normal of a vertex.
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fn normal(&self, face: usize, vert: usize) -> [f32; 3];
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/// Returns the texture coordinate of a vertex.
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fn tex_coord(&self, face: usize, vert: usize) -> [f32; 2];
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/// Sets the generated tangent for a vertex.
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/// Leave this function unimplemented if you are implementing
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/// `set_tangent_encoded`.
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fn set_tangent(
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&mut self,
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tangent: [f32; 3],
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_bi_tangent: [f32; 3],
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_f_mag_s: f32,
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_f_mag_t: f32,
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bi_tangent_preserves_orientation: bool,
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face: usize,
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vert: usize,
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) {
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let sign = if bi_tangent_preserves_orientation {
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1.0
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} else {
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-1.0
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};
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self.set_tangent_encoded([tangent[0], tangent[1], tangent[2], sign], face, vert);
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}
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/// Sets the generated tangent for a vertex with its bi-tangent encoded as the 'W' (4th)
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/// component in the tangent. The 'W' component marks if the bi-tangent is flipped. This
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/// is called by the default implementation of `set_tangent`; therefore, this function will
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/// not be called by the crate unless `set_tangent` is unimplemented.
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fn set_tangent_encoded(&mut self, _tangent: [f32; 4], _face: usize, _vert: usize) {}
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}
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/// Generates tangents for the input geometry.
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///
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/// # Errors
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///
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/// Returns `false` if the geometry is unsuitable for tangent generation including,
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/// but not limited to, lack of vertices.
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pub fn generate_tangents<I: Geometry>(geometry: &mut I) -> bool {
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unsafe { generated::genTangSpace(geometry, 180.0) }
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}
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fn get_position<I: Geometry>(geometry: &mut I, index: usize) -> Vec3 {
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let (face, vert) = index_to_face_vert(index);
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geometry.position(face, vert).into()
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}
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fn get_tex_coord<I: Geometry>(geometry: &mut I, index: usize) -> Vec3 {
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let (face, vert) = index_to_face_vert(index);
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let tex_coord: Vec2 = geometry.tex_coord(face, vert).into();
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let val = tex_coord.extend(1.0);
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val
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}
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fn get_normal<I: Geometry>(geometry: &mut I, index: usize) -> Vec3 {
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let (face, vert) = index_to_face_vert(index);
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geometry.normal(face, vert).into()
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}
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fn index_to_face_vert(index: usize) -> (usize, usize) {
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(index >> 2, index & 0x3)
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}
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fn face_vert_to_index(face: usize, vert: usize) -> usize {
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face << 2 | vert & 0x3
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}
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