DiffVG/within_distance.h

#pragma once

#include "diffvg.h"
#include "edge_query.h"
#include "shape.h"
#include "vector.h"

DEVICE
inline
bool within_distance(const Circle &circle, const Vector2f &pt, float r) {
    auto dist_to_center = distance(circle.center, pt);
    if (fabs(dist_to_center - circle.radius) < r) {
        return true;
    }
    return false;
}

DEVICE
inline
bool within_distance(const Path &path, const BVHNode *bvh_nodes, const Vector2f &pt, float r) {
    auto num_segments = path.num_base_points;
    constexpr auto max_bvh_size = 128;
    int bvh_stack[max_bvh_size];
    auto stack_size = 0;
    bvh_stack[stack_size++] = 2 * num_segments - 2;
    while (stack_size > 0) {
        const BVHNode &node = bvh_nodes[bvh_stack[--stack_size]];
        if (node.child1 < 0) {
            // leaf
            auto base_point_id = node.child0;
            auto point_id = - node.child1 - 1;
            assert(base_point_id < num_segments);
            assert(point_id < path.num_points);
            if (path.num_control_points[base_point_id] == 0) {
                // Straight line
                auto i0 = point_id;
                auto i1 = (point_id + 1) % path.num_points;
                auto p0 = Vector2f{path.points[2 * i0], path.points[2 * i0 + 1]};
                auto p1 = Vector2f{path.points[2 * i1], path.points[2 * i1 + 1]};
                // project pt to line
                auto t = dot(pt - p0, p1 - p0) / dot(p1 - p0, p1 - p0);
                auto r0 = r;
                auto r1 = r;
                // override radius if path has thickness
                if (path.thickness != nullptr) {
                    r0 = path.thickness[i0];
                    r1 = path.thickness[i1];
                }
                if (t < 0) {
                    if (distance_squared(p0, pt) < r0 * r0) {
                        return true;
                    }
                } else if (t > 1) {
                    if (distance_squared(p1, pt) < r1 * r1) {
                        return true;
                    }
                } else {
                    auto r = r0 + t * (r1 - r0);
                    if (distance_squared(p0 + t * (p1 - p0), pt) < r * r) {
                        return true;
                    }
                }
            } else if (path.num_control_points[base_point_id] == 1) {
                // Quadratic Bezier curve
                auto i0 = point_id;
                auto i1 = point_id + 1;
                auto i2 = (point_id + 2) % path.num_points;
                auto p0 = Vector2f{path.points[2 * i0], path.points[2 * i0 + 1]};
                auto p1 = Vector2f{path.points[2 * i1], path.points[2 * i1 + 1]};
                auto p2 = Vector2f{path.points[2 * i2], path.points[2 * i2 + 1]};
                if (path.use_distance_approx) {
                    auto cp = quadratic_closest_pt_approx(p0, p1, p2, pt);
                    return distance_squared(cp, pt) < r * r;
                }
                auto eval = [&](float t) -> Vector2f {
                    auto tt = 1 - t;
                    return (tt*tt)*p0 + (2*tt*t)*p1 + (t*t)*p2;
                };
                auto r0 = r;
                auto r1 = r;
                auto r2 = r;
                // override radius if path has thickness
                if (path.thickness != nullptr) {
                    r0 = path.thickness[i0];
                    r1 = path.thickness[i1];
                    r2 = path.thickness[i2];
                }
                if (distance_squared(eval(0), pt) < r0 * r0) {
                    return true;
                }
                if (distance_squared(eval(1), pt) < r2 * r2) {
                    return true;
                }

                // The curve is (1-t)^2p0 + 2(1-t)tp1 + t^2p2
                // = (p0-2p1+p2)t^2+(-2p0+2p1)t+p0 = q
                // Want to solve (q - pt) dot q' = 0
                // q' = (p0-2p1+p2)t + (-p0+p1)
                // Expanding (p0-2p1+p2)^2 t^3 +
                //           3(p0-2p1+p2)(-p0+p1) t^2 +
                //           (2(-p0+p1)^2+(p0-2p1+p2)(p0-pt))t +
                //           (-p0+p1)(p0-pt) = 0
                auto A = sum((p0-2*p1+p2)*(p0-2*p1+p2));
                auto B = sum(3*(p0-2*p1+p2)*(-p0+p1));
                auto C = sum(2*(-p0+p1)*(-p0+p1)+(p0-2*p1+p2)*(p0-pt));
                auto D = sum((-p0+p1)*(p0-pt));
                float t[3];
                int num_sol = solve_cubic(A, B, C, D, t);
                for (int j = 0; j < num_sol; j++) {
                    if (t[j] >= 0 && t[j] <= 1) {
                        auto tt = 1 - t[j];
                        auto r = (tt*tt)*r0 + (2*tt*t[j])*r1 + (t[j]*t[j])*r2;
                        auto p = eval(t[j]);
                        if (distance_squared(p, pt) < r*r) {
                            return true;
                        }
                    }
                }
            } else if (path.num_control_points[base_point_id] == 2) {
                // Cubic Bezier curve
                auto i0 = point_id;
                auto i1 = point_id + 1;
                auto i2 = point_id + 2;
                auto i3 = (point_id + 3) % path.num_points;
                auto p0 = Vector2f{path.points[2 * i0], path.points[2 * i0 + 1]};
                auto p1 = Vector2f{path.points[2 * i1], path.points[2 * i1 + 1]};
                auto p2 = Vector2f{path.points[2 * i2], path.points[2 * i2 + 1]};
                auto p3 = Vector2f{path.points[2 * i3], path.points[2 * i3 + 1]};
                auto eval = [&](float t) -> Vector2f {
                    auto tt = 1 - t;
                    return (tt*tt*tt)*p0 + (3*tt*tt*t)*p1 + (3*tt*t*t)*p2 + (t*t*t)*p3;
                };
                auto r0 = r;
                auto r1 = r;
                auto r2 = r;
                auto r3 = r;
                // override radius if path has thickness
                if (path.thickness != nullptr) {
                    r0 = path.thickness[i0];
                    r1 = path.thickness[i1];
                    r2 = path.thickness[i2];
                    r3 = path.thickness[i3];
                }
                if (distance_squared(eval(0), pt) < r0*r0) {
                    return true;
                }
                if (distance_squared(eval(1), pt) < r3*r3) {
                    return true;
                }
                // The curve is (1 - t)^3 p0 + 3 * (1 - t)^2 t p1 + 3 * (1 - t) t^2 p2 + t^3 p3
                // = (-p0+3p1-3p2+p3) t^3 + (3p0-6p1+3p2) t^2 + (-3p0+3p1) t + p0
                // Want to solve (q - pt) dot q' = 0
                // q' = 3*(-p0+3p1-3p2+p3)t^2 + 2*(3p0-6p1+3p2)t + (-3p0+3p1)
                // Expanding 
                // 3*(-p0+3p1-3p2+p3)^2 t^5
                // 5*(-p0+3p1-3p2+p3)(3p0-6p1+3p2) t^4
                // 4*(-p0+3p1-3p2+p3)(-3p0+3p1) + 2*(3p0-6p1+3p2)^2 t^3
                // 3*(3p0-6p1+3p2)(-3p0+3p1) + 3*(-p0+3p1-3p2+p3)(p0-pt) t^2
                // (-3p0+3p1)^2+2(p0-pt)(3p0-6p1+3p2) t
                // (p0-pt)(-3p0+3p1)
                double A = 3*sum((-p0+3*p1-3*p2+p3)*(-p0+3*p1-3*p2+p3));
                double B = 5*sum((-p0+3*p1-3*p2+p3)*(3*p0-6*p1+3*p2));
                double C = 4*sum((-p0+3*p1-3*p2+p3)*(-3*p0+3*p1)) + 2*sum((3*p0-6*p1+3*p2)*(3*p0-6*p1+3*p2));
                double D = 3*(sum((3*p0-6*p1+3*p2)*(-3*p0+3*p1)) + sum((-p0+3*p1-3*p2+p3)*(p0-pt)));
                double E = sum((-3*p0+3*p1)*(-3*p0+3*p1)) + 2*sum((p0-pt)*(3*p0-6*p1+3*p2));
                double F = sum((p0-pt)*(-3*p0+3*p1));
                // normalize the polynomial
                B /= A;
                C /= A;
                D /= A;
                E /= A;
                F /= A;
                // Isolator Polynomials:
                // https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.133.2233&rep=rep1&type=pdf
                //                                       x/5 + B/25
                //                                    /-----------------------------------------------------
                // 5x^4 + 4B x^3 + 3C x^2 + 2D x + E /   x^5 +    B x^4 +       C x^3 +      D x^2 +      E x + F
                //                                       x^5 + 4B/5 x^4 +    3C/5 x^3 +   2D/5 x^2 +    E/5 x
                //                                      ----------------------------------------------------
                //                                              B/5 x^4 +    2C/5 x^3 +   3D/5 x^2 +   4E/5 x + F
                //                                              B/5 x^4 + 4B^2/25 x^3 + 3BC/25 x^2 + 2BD/25 x + BE/25
                //                                      ----------------------------------------------------
                //                                     (2C/5 - 4B^2/25)x^3 + (3D/5-3BC/25)x^2 + (4E/5-2BD/25) + (F-BE/25)
                auto p1A = ((2 / 5.f) * C - (4 / 25.f) * B * B);
                auto p1B = ((3 / 5.f) * D - (3 / 25.f) * B * C);
                auto p1C = ((4 / 5.f) * E - (2 / 25.f) * B * D);
                auto p1D = F - B * E / 25.f;
                // auto q1A = 1 / 5.f;
                // auto q1B = B / 25.f;
                // x/5 + B/25 = 0
                // x = -B/5
                auto q_root = -B/5.f;
                double p_roots[3];
                int num_sol = solve_cubic(p1A, p1B, p1C, p1D, p_roots);
                float intervals[4];
                if (q_root >= 0 && q_root <= 1) {
                    intervals[0] = q_root;
                }
                for (int j = 0; j < num_sol; j++) {
                    intervals[j + 1] = p_roots[j];
                }
                auto num_intervals = 1 + num_sol;
                // sort intervals
                for (int j = 1; j < num_intervals; j++) {
                    for (int k = j; k > 0 && intervals[k - 1] > intervals[k]; k--) {
                        auto tmp = intervals[k];
                        intervals[k] = intervals[k - 1];
                        intervals[k - 1] = tmp;
                    }
                }
                auto eval_polynomial = [&] (double t) {
                    return t*t*t*t*t+
                           B*t*t*t*t+
                           C*t*t*t+
                           D*t*t+
                           E*t+
                           F;
                };
                auto eval_polynomial_deriv = [&] (double t) {
                    return 5*t*t*t*t+
                           4*B*t*t*t+
                           3*C*t*t+
                           2*D*t+
                           E;
                };
                auto lower_bound = 0.f;
                for (int j = 0; j < num_intervals + 1; j++) {
                    if (j < num_intervals && intervals[j] < 0.f) {
                        continue;
                    }
                    auto upper_bound = j < num_intervals ?
                        min(intervals[j], 1.f) : 1.f;
                    auto lb = lower_bound;
                    auto ub = upper_bound;
                    auto lb_eval = eval_polynomial(lb);
                    auto ub_eval = eval_polynomial(ub);
                    if (lb_eval * ub_eval > 0) {
                        // Doesn't have root
                        continue;
                    }
                    if (lb_eval > ub_eval) {
                        swap_(lb, ub);
                    }
                    auto t = 0.5f * (lb + ub);
                    for (int it = 0; it < 20; it++) {
                        if (!(t >= lb && t <= ub)) {
                            t = 0.5f * (lb + ub);
                        }
                        auto value = eval_polynomial(t);
                        if (fabs(value) < 1e-5f || it == 19) {
                            break;
                        }
                        // The derivative may not be entirely accurate,
                        // but the bisection is going to handle this
                        if (value > 0.f) {
                            ub = t;
                        } else {
                            lb = t;
                        }
                        auto derivative = eval_polynomial_deriv(t);
                        t -= value / derivative;
                    }
                    auto tt = 1 - t;
                    auto r = (tt*tt*tt)*r0 + (3*tt*tt*t)*r1 + (3*tt*t*t)*r2 + (t*t*t)*r3;
                    if (distance_squared(eval(t), pt) < r * r) {
                        return true;
                    }
                    if (upper_bound >= 1.f) {
                        break;
                    }
                    lower_bound = upper_bound;
                }
            } else {
                assert(false);
            }
        } else {
            assert(node.child0 >= 0 && node.child1 >= 0);
            const AABB &b0 = bvh_nodes[node.child0].box;
            if (within_distance(b0, pt, bvh_nodes[node.child0].max_radius)) {
                bvh_stack[stack_size++] = node.child0;
            }
            const AABB &b1 = bvh_nodes[node.child1].box;
            if (within_distance(b1, pt, bvh_nodes[node.child1].max_radius)) {
                bvh_stack[stack_size++] = node.child1;
            }
            assert(stack_size <= max_bvh_size);
        }
    }
    return false;
}

DEVICE
inline
int within_distance(const Rect &rect, const Vector2f &pt, float r) {
    auto test = [&](const Vector2f &p0, const Vector2f &p1) {
        // project pt to line
        auto t = dot(pt - p0, p1 - p0) / dot(p1 - p0, p1 - p0);
        if (t < 0) {
            if (distance_squared(p0, pt) < r * r) {
                return true;
            }
        } else if (t > 1) {
            if (distance_squared(p1, pt) < r * r) {
                return true;
            }
        } else {
            if (distance_squared(p0 + t * (p1 - p0), pt) < r * r) {
                return true;
            }
        }
        return false;
    };
    auto left_top = rect.p_min;
    auto right_top = Vector2f{rect.p_max.x, rect.p_min.y};
    auto left_bottom = Vector2f{rect.p_min.x, rect.p_max.y};
    auto right_bottom = rect.p_max;
    // left
    if (test(left_top, left_bottom)) {
        return true;
    }
    // top
    if (test(left_top, right_top)) {
        return true;
    }
    // right
    if (test(right_top, right_bottom)) {
        return true;
    }
    // bottom
    if (test(left_bottom, right_bottom)) {
        return true;
    }
    return false;
}

DEVICE
inline
bool within_distance(const Shape &shape, const BVHNode *bvh_nodes, const Vector2f &pt, float r) {
    switch (shape.type) {
        case ShapeType::Circle:
            return within_distance(*(const Circle *)shape.ptr, pt, r);
        case ShapeType::Ellipse:
            // https://www.geometrictools.com/Documentation/DistancePointEllipseEllipsoid.pdf
            assert(false);
            return false;
        case ShapeType::Path:
            return within_distance(*(const Path *)shape.ptr, bvh_nodes, pt, r);
        case ShapeType::Rect:
            return within_distance(*(const Rect *)shape.ptr, pt, r);
    }
    assert(false);
    return false;
}

DEVICE
inline
bool within_distance(const SceneData &scene,
                     int shape_group_id,
                     const Vector2f &pt) {
    const ShapeGroup &shape_group = scene.shape_groups[shape_group_id];
    // pt is in canvas space, transform it to shape's local space
    auto local_pt = xform_pt(shape_group.canvas_to_shape, pt);

    constexpr auto max_bvh_stack_size = 64;
    int bvh_stack[max_bvh_stack_size];
    auto stack_size = 0;
    bvh_stack[stack_size++] = 2 * shape_group.num_shapes - 2;
    const auto &bvh_nodes = scene.shape_groups_bvh_nodes[shape_group_id];

    while (stack_size > 0) {
        const BVHNode &node = bvh_nodes[bvh_stack[--stack_size]];
        if (node.child1 < 0) {
            // leaf
            auto shape_id = node.child0;
            const auto &shape = scene.shapes[shape_id];
            if (within_distance(shape, scene.path_bvhs[shape_id],
                                local_pt, shape.stroke_width)) {
                return true;
            }
        } else {
            assert(node.child0 >= 0 && node.child1 >= 0);
            const AABB &b0 = bvh_nodes[node.child0].box;
            if (inside(b0, local_pt, bvh_nodes[node.child0].max_radius)) {
                bvh_stack[stack_size++] = node.child0;
            }
            const AABB &b1 = bvh_nodes[node.child1].box;
            if (inside(b1, local_pt, bvh_nodes[node.child1].max_radius)) {
                bvh_stack[stack_size++] = node.child1;
            }
            assert(stack_size <= max_bvh_stack_size);
        }
    }

    return false;
}

DEVICE
inline
bool within_distance(const SceneData &scene,
                     int shape_group_id,
                     const Vector2f &pt,
                     EdgeQuery *edge_query) {
    if (edge_query == nullptr || shape_group_id != edge_query->shape_group_id) {
        // Specialized version
        return within_distance(scene, shape_group_id, pt);
    }
    const ShapeGroup &shape_group = scene.shape_groups[shape_group_id];
    // pt is in canvas space, transform it to shape's local space
    auto local_pt = xform_pt(shape_group.canvas_to_shape, pt);

    constexpr auto max_bvh_stack_size = 64;
    int bvh_stack[max_bvh_stack_size];
    auto stack_size = 0;
    bvh_stack[stack_size++] = 2 * shape_group.num_shapes - 2;
    const auto &bvh_nodes = scene.shape_groups_bvh_nodes[shape_group_id];

    auto ret = false;
    while (stack_size > 0) {
        const BVHNode &node = bvh_nodes[bvh_stack[--stack_size]];
        if (node.child1 < 0) {
            // leaf
            auto shape_id = node.child0;
            const auto &shape = scene.shapes[shape_id];
            if (within_distance(shape, scene.path_bvhs[shape_id],
                                local_pt, shape.stroke_width)) {
                ret = true;
                if (shape_id == edge_query->shape_id) {
                    edge_query->hit = true;
                }
            }
        } else {
            assert(node.child0 >= 0 && node.child1 >= 0);
            const AABB &b0 = bvh_nodes[node.child0].box;
            if (inside(b0, local_pt, bvh_nodes[node.child0].max_radius)) {
                bvh_stack[stack_size++] = node.child0;
            }
            const AABB &b1 = bvh_nodes[node.child1].box;
            if (inside(b1, local_pt, bvh_nodes[node.child1].max_radius)) {
                bvh_stack[stack_size++] = node.child1;
            }
            assert(stack_size <= max_bvh_stack_size);
        }
    }

    return ret;
}