aobench - Siv3D/Reference-JP GitHub Wiki

# include <Siv3D.hpp>
const int32 WIDTH = 480;
const int32 HEIGHT = 480;
const int32 NSUBSAMPLES = 2;
const int32 NAO_SAMPLES = 8;

namespace ao
{
    struct Isect
    {
        double t;
        Vec3   p;
        Vec3   n;
        int32  hit;
    };

    struct Sphere
    {
        Vec3   center;
        double radius;
    };

    struct Plane
    {
        Vec3 p;
        Vec3 n;
    };

    struct Ray
    {
        Vec3 org;
        Vec3 dir;
    };

    Sphere spheres[3];

    Plane plane;

    void ray_sphere_intersect(Isect* isect, const Ray& ray, const Sphere& sphere)
    {
        const Vec3 rs = ray.org - sphere.center;
        const double B = rs.dot(ray.dir);
        const double C = rs.dot(rs) - sphere.radius * sphere.radius;
        const double D = B * B - C;

        if (D > 0.0)
        {
            const double t = -B - Sqrt(D);

            if ((t > 0.0) && (t < isect->t))
            {
                isect->t = t;
                isect->hit = 1;
                isect->p = ray.org + ray.dir * t;
                isect->n = (isect->p - sphere.center).normalized();
            }
        }
    }

    void ray_plane_intersect(Isect* isect, const Ray& ray, const Plane& _plane)
    {
        const double d = -_plane.p.dot(_plane.n);
        const double v = ray.dir.dot(_plane.n);

        if (Abs(v) < 1.0e-17)
        {
            return;
        }

        const double t = -(ray.org.dot(_plane.n) + d) / v;

        if ((t > 0.0) && (t < isect->t))
        {
            isect->t = t;
            isect->hit = 1;
            isect->p = ray.org + ray.dir * t;
            isect->n = _plane.n;
        }
    }

    std::array<Vec3, 3> orthoBasis(const Vec3& n)
    {
        std::array<Vec3, 3> basis;

        basis[2] = n;
        basis[1].set(0.0, 0.0, 0.0);

        if ((n.x < 0.6) && (n.x > -0.6))
        {
            basis[1].x = 1.0;
        }
        else if ((n.y < 0.6) && (n.y > -0.6))
        {
            basis[1].y = 1.0;
        }
        else if ((n.z < 0.6) && (n.z > -0.6))
        {
            basis[1].z = 1.0;
        }
        else
        {
            basis[1].x = 1.0;
        }

        basis[0] = basis[1].cross(basis[2]).normalized();
        basis[1] = basis[2].cross(basis[0]).normalized();

        return basis;
    }

    Vec3 ambient_occlusion(const Isect& isect)
    {
        const int32 ntheta = NAO_SAMPLES;
        const int32 nphi = NAO_SAMPLES;
        const double eps = 0.0001;
        const Vec3 p = isect.p + eps * isect.n;
        const std::array<Vec3, 3> basis = orthoBasis(isect.n);

        double occlusion = 0.0;

        for (int32 j = 0; j < ntheta; ++j)
        {
            for (int32 i = 0; i < nphi; ++i)
            {
                const double theta = Sqrt(Random());
                const double phi = TwoPi * Random();

                const double x = Cos(phi) * theta;
                const double y = Sin(phi) * theta;
                const double z = Sqrt(1.0 - theta * theta);

                const double rx = x * basis[0].x + y * basis[1].x + z * basis[2].x;
                const double ry = x * basis[0].y + y * basis[1].y + z * basis[2].y;
                const double rz = x * basis[0].z + y * basis[1].z + z * basis[2].z;

                const Ray ray = { p,{ rx, ry, rz } };

                Isect occIsect;
                occIsect.t = 1.0e+17;
                occIsect.hit = 0;

                ray_sphere_intersect(&occIsect, ray, spheres[0]);
                ray_sphere_intersect(&occIsect, ray, spheres[1]);
                ray_sphere_intersect(&occIsect, ray, spheres[2]);
                ray_plane_intersect(&occIsect, ray, plane);

                if (occIsect.hit)
                {
                    occlusion += 1.0;
                }
            }
        }

        occlusion = (ntheta * nphi - occlusion) / (ntheta * nphi);

        return{ occlusion, occlusion, occlusion };
    }

    void render(Image& image, const int32 w, const int32 h, const int32 nsubsamples)
    {
        for (int32 y = 0; y < h; ++y)
        {
            for (int32 x = 0; x < w; ++x)
            {
                Vec3 color{ 0.0, 0.0, 0.0 };

                for (int32 v = 0; v < nsubsamples; ++v)
                {
                    for (int32 u = 0; u < nsubsamples; ++u)
                    {
                        const double px = (x + (u / static_cast<double>(nsubsamples)) - (w / 2.0)) / (w / 2.0);
                        const double py = -(y + (v / static_cast<double>(nsubsamples)) - (h / 2.0)) / (h / 2.0);

                        const Ray ray = { { 0.0, 0.0, 0.0 }, Vec3{ px, py, -1.0 }.normalized() };

                        Isect isect;
                        isect.t = 1.0e+17;
                        isect.hit = 0;

                        ray_sphere_intersect(&isect, ray, spheres[0]);
                        ray_sphere_intersect(&isect, ray, spheres[1]);
                        ray_sphere_intersect(&isect, ray, spheres[2]);
                        ray_plane_intersect(&isect, ray, plane);

                        if (isect.hit)
                        {
                            color += ambient_occlusion(isect);
                        }
                    }
                }

                color /= nsubsamples * nsubsamples;

                image[y][x] = ColorF{ color.x, color.y, color.z };
            }
        }
    }

    void init_scene()
    {
        spheres[0].center.set(-2.0, 0.0, -3.5);
        spheres[0].radius = 0.5;

        spheres[1].center.set(-0.5, 0.0, -3.0);
        spheres[1].radius = 0.5;

        spheres[2].center.set(1.0, 0.0, -2.2);
        spheres[2].radius = 0.5;

        plane.p.set(0.0, -0.5, 0.0);
        plane.n.set(0.0, 1.0, 0.0);
    }
}

void Main()
{
    ao::init_scene();

    Image image(WIDTH, HEIGHT);

    Stopwatch stopwatch(true);

    ao::render(image, WIDTH, HEIGHT, NSUBSAMPLES);

    Println(stopwatch.ms(), L"ms");

    Texture(image).draw();

    WaitKey();
}