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// This file is part of the 64k demo project.
// Möller-Trumbore ray-triangle intersection algorithm.
// Reference: "Fast, Minimum Storage Ray-Triangle Intersection"
struct TriangleHit {
uv: vec2<f32>,
z: f32,
N: vec3<f32>,
hit: bool,
};
fn ray_triangle_intersection(
orig: vec3<f32>,
dir: vec3<f32>,
p0: vec3<f32>,
p1: vec3<f32>,
p2: vec3<f32>
) -> TriangleHit {
let d10 = p1 - p0;
let d20 = p2 - p0;
let N = cross(d10, d20);
let det = -dot(dir, N);
let invdet = 1.0 / det;
let d0 = orig - p0;
let nd = cross(d0, dir);
let uv = vec2<f32>(dot(d20, nd), -dot(d10, nd)) * invdet;
let z = dot(d0, N) * invdet;
let hit = det > 0.0 && z >= 0.0 && uv.x >= 0.0 && uv.y >= 0.0 && (uv.x + uv.y) < 1.0;
return TriangleHit(uv, z, N, hit);
}
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