tiny.geometry.Mesh

1/// A borrowed triangle list: triangle `i` joins the positions named by2/// `indices[3 i .. 3 i + 3]`.3pub const Mesh = struct {4    positions: []const Vec3,5    indices: []const u32,67    pub fn triangleCount(mesh: Mesh) usize {8        assert(mesh.indices.len % 3 == 0);9        return mesh.indices.len / 3;10    }1112    /// Whether the index list names whole triangles over existing, finite13    /// positions, within `max_triangles`.14    pub fn isWellFormed(mesh: Mesh) bool {15        if (mesh.indices.len % 3 != 0) return false;16        if (mesh.indices.len / 3 > max_triangles) return false;17        for (mesh.indices) |index| {18            if (index >= mesh.positions.len) return false;19        }20        for (mesh.positions) |p| {21            if (!std.math.isFinite(p.x) or !std.math.isFinite(p.y) or !std.math.isFinite(p.z)) return false;22        }23        return true;24    }2526    pub fn triangle(mesh: Mesh, index: usize) Triangle {27        const base = index * 3;28        assert(base + 3 <= mesh.indices.len);29        return .{30            .a = mesh.positions[mesh.indices[base + 0]],31            .b = mesh.positions[mesh.indices[base + 1]],32            .c = mesh.positions[mesh.indices[base + 2]],33        };34    }3536    /// The box around every triangle, empty for a mesh with none.37    pub fn bounds(mesh: Mesh) Aabb {38        var box = Aabb.empty;39        for (mesh.indices) |index| box = box.joinPoint(mesh.positions[index]);40        return box;41    }4243    /// The nearest triangle the ray meets with `t` in `[t_min, t_max]`.44    pub fn raycast(mesh: Mesh, ray: Ray, t_min: f32, t_max: f32) ?RayHit {45        assert(t_min <= t_max);46        var best: ?RayHit = null;47        for (0..mesh.triangleCount()) |index| {48            const hit = intersect.rayTriangle(ray, mesh.triangle(index)) orelse continue;49            if (hit.t < t_min or hit.t > t_max) continue;50            if (best) |held| {51                if (hit.t >= held.t) continue;52            }53            best = .{ .t = hit.t, .u = hit.u, .v = hit.v, .triangle = @intCast(index) };54        }55        return best;56    }5758    /// Whether the ray meets any triangle with `t` in `[t_min, t_max]`.59    pub fn raycastAny(mesh: Mesh, ray: Ray, t_min: f32, t_max: f32) bool {60        assert(t_min <= t_max);61        for (0..mesh.triangleCount()) |index| {62            const hit = intersect.rayTriangle(ray, mesh.triangle(index)) orelse continue;63            if (hit.t >= t_min and hit.t <= t_max) return true;64        }65        return false;66    }6768    /// The triangles the sphere touches, lowest indices first, into `out`.69    pub fn overlapSphere(mesh: Mesh, sphere: Sphere, out: []u32) Overlap {70        var count: usize = 0;71        for (0..mesh.triangleCount()) |index| {72            if (!intersect.sphereTriangle(sphere, mesh.triangle(index))) continue;73            if (count == out.len) return .{ .count = count, .complete = false };74            out[count] = @intCast(index);75            count += 1;76        }77        return .{ .count = count, .complete = true };78    }7980    /// The triangles the capsule touches, lowest indices first, into `out`.81    pub fn overlapCapsule(mesh: Mesh, capsule: Capsule, out: []u32) Overlap {82        var count: usize = 0;83        for (0..mesh.triangleCount()) |index| {84            if (!intersect.capsuleTriangle(capsule, mesh.triangle(index))) continue;85            if (count == out.len) return .{ .count = count, .complete = false };86            out[count] = @intCast(index);87            count += 1;88        }89        return .{ .count = count, .complete = true };90    }9192    /// The first triangle the sphere touches as it moves by `displacement`.93    pub fn sweepSphere(mesh: Mesh, sphere: Sphere, displacement: Vec3) ?SweepHit {94        var best: ?SweepHit = null;95        for (0..mesh.triangleCount()) |index| {96            const hit = sweep.sphereTriangle(sphere, displacement, mesh.triangle(index)) orelse continue;97            if (best) |held| {98                if (hit.t >= held.t) continue;99            }100            best = .{ .t = hit.t, .point = hit.point, .normal = hit.normal, .triangle = @intCast(index) };101        }102        return best;103    }104105    /// The first triangle the capsule touches as it moves by `displacement`.106    pub fn sweepCapsule(mesh: Mesh, capsule: Capsule, displacement: Vec3) ?SweepHit {107        var best: ?SweepHit = null;108        for (0..mesh.triangleCount()) |index| {109            const hit = sweep.capsuleTriangle(capsule, displacement, mesh.triangle(index)) orelse continue;110            if (best) |held| {111                if (hit.t >= held.t) continue;112            }113            best = .{ .t = hit.t, .point = hit.point, .normal = hit.normal, .triangle = @intCast(index) };114        }115        return best;116    }117};

1pub const Mesh = mesh.Mesh;