bevy/crates/bevy_mikktspace/src/lib.rs

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#![allow(clippy::type_complexity)]
Generate vertex tangents using mikktspace (#3872) # 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>
2022-05-31 22:53:54 +00:00
#![allow(clippy::all)]
use glam::{Vec2, Vec3};
mod generated;
/// The interface by which mikktspace interacts with your geometry.
pub trait Geometry {
/// Returns the number of faces.
fn num_faces(&self) -> usize;
/// Returns the number of vertices of a face.
fn num_vertices_of_face(&self, face: usize) -> usize;
/// Returns the position of a vertex.
fn position(&self, face: usize, vert: usize) -> [f32; 3];
/// Returns the normal of a vertex.
fn normal(&self, face: usize, vert: usize) -> [f32; 3];
/// Returns the texture coordinate of a vertex.
fn tex_coord(&self, face: usize, vert: usize) -> [f32; 2];
/// Sets the generated tangent for a vertex.
/// Leave this function unimplemented if you are implementing
/// `set_tangent_encoded`.
fn set_tangent(
&mut self,
tangent: [f32; 3],
_bi_tangent: [f32; 3],
_f_mag_s: f32,
_f_mag_t: f32,
bi_tangent_preserves_orientation: bool,
face: usize,
vert: usize,
) {
let sign = if bi_tangent_preserves_orientation {
1.0
} else {
-1.0
};
self.set_tangent_encoded([tangent[0], tangent[1], tangent[2], sign], face, vert);
}
/// Sets the generated tangent for a vertex with its bi-tangent encoded as the 'W' (4th)
/// component in the tangent. The 'W' component marks if the bi-tangent is flipped. This
/// is called by the default implementation of `set_tangent`; therefore, this function will
/// not be called by the crate unless `set_tangent` is unimplemented.
fn set_tangent_encoded(&mut self, _tangent: [f32; 4], _face: usize, _vert: usize) {}
}
/// Generates tangents for the input geometry.
///
/// # Errors
///
/// Returns `false` if the geometry is unsuitable for tangent generation including,
/// but not limited to, lack of vertices.
pub fn generate_tangents<I: Geometry>(geometry: &mut I) -> bool {
unsafe { generated::genTangSpace(geometry, 180.0) }
}
fn get_position<I: Geometry>(geometry: &mut I, index: usize) -> Vec3 {
let (face, vert) = index_to_face_vert(index);
geometry.position(face, vert).into()
}
fn get_tex_coord<I: Geometry>(geometry: &mut I, index: usize) -> Vec3 {
let (face, vert) = index_to_face_vert(index);
let tex_coord: Vec2 = geometry.tex_coord(face, vert).into();
let val = tex_coord.extend(1.0);
val
}
fn get_normal<I: Geometry>(geometry: &mut I, index: usize) -> Vec3 {
let (face, vert) = index_to_face_vert(index);
geometry.normal(face, vert).into()
}
fn index_to_face_vert(index: usize) -> (usize, usize) {
(index >> 2, index & 0x3)
}
fn face_vert_to_index(face: usize, vert: usize) -> usize {
face << 2 | vert & 0x3
}