Crate uvgen

UV Map generator. Used to generate second texture coordinates for light maps.

Current implementation uses simple tri-planar mapping.

Example

#[derive(Copy, Clone, Debug, Default, PartialEq)]
pub struct Vertex {
    pub position: Vector3<f32>,
    pub tex_coord: Vector2<f32>,
}

impl Vertex {
    fn new(x: f32, y: f32, z: f32) -> Self {
        Self {
            position: Vector3::new(x, y, z),
            tex_coord: Default::default(),
        }
    }
}

// Create cube geometry.
let mut vertices = vec![
    Vertex::new(-0.5, -0.5, 0.5),
    Vertex::new(-0.5, 0.5, 0.5),
    Vertex::new(0.5, 0.5, 0.5),
    Vertex::new(0.5, -0.5, 0.5),
    Vertex::new(-0.5, -0.5, -0.5),
    Vertex::new(-0.5, 0.5, -0.5),
    Vertex::new(0.5, 0.5, -0.5),
    Vertex::new(0.5, -0.5, -0.5),
];

let mut triangles = vec![
    // Front
    [2, 1, 0],
    [3, 2, 0],
    // Back
    [4, 5, 6],
    [4, 6, 7],
    // Right
    [7, 6, 2],
    [2, 3, 7],
    // Left
    [0, 1, 5],
    [0, 5, 4],
    // Top
    [5, 1, 2],
    [5, 2, 6],
    // Bottom
    [3, 0, 4],
    [7, 3, 4],
];

let patch = uvgen::generate_uvs(
    vertices.iter().map(|v| v.position),
    triangles.iter().cloned(),
    0.005,
).unwrap();

// Apply patch to the initial data.
triangles = patch.triangles;
for &vertex_index in &patch.additional_vertices {
    let vertex = vertices[vertex_index as usize];
    vertices.push(vertex);
}

// Assign generated texture coordinates.
for (vertex, tex_coord) in vertices.iter_mut().zip(&patch.second_tex_coords) {
    vertex.tex_coord = *tex_coord;
}

Structs

SurfaceDataPatch

A patch for surface data that contains secondary texture coordinates and new topology for data. It is needed for serialization: during the UV generation, generator could multiply vertices to make seams, it adds new data to existing vertices. The problem is that we do not serialize surface data - we store only a “link” to resource from which we’ll load surface data on deserialization. But freshly loaded resource is not suitable for generated lightmap - in most cases it just does not have secondary texture coordinates. So we have to patch data after loading somehow with required data, this is where SurfaceDataPatch comes into play.

Functions

generate_uvs

Generates UV map for the given vertices and triangles.