【Ray Tracing in One Weekend 超詳解】 光線追蹤1-10

 

《Ray Tracing in One Weekend》完結篇

最近課程上機實驗，封面圖渲染時間也超長，所以寫東西就落下了，見諒

這篇之后，我會繼續《Ray Tracing The Next Week》，還請多多關注

 

這幾天我在渲染這本書的封面圖，封面圖還沒出，不算結束，剛好安排了10節

今天呢，有兩件事：

1.闡述整個工程的文件組織即內容

2.闡述封面，完結

 

 

12.1工程文件組織

試過很多方法，問過很多老師，無奈，子類繼承實現的父類純虛函數實在無法和類聲明分成兩個文件（即聲明放於.h，其他實現放在.cpp中），室友說，純虛函數繼承實現和模板很類似

所以，我們在合適的時候使用hpp

在學習過程中，我們遇到了諸如反射、折射之類的函數，它們並不應該屬於某個具體子類，或者抽象基類

所以，我把它們寫在了泛型3D數學庫里面了

C++泛型3D數學庫是我們學光線追蹤的數學專用庫了吧算是

向量庫

基礎光學幾何函數庫

 

在回頭看我們的光線追蹤的項目代碼

1.工程定義文件

我們之前是在ray這個最基本的類中定義了一些基本的命名，爾后，發現，所有的東西都要用ray::val_type諸如此類的代碼去描述光線追蹤所用到的一些普遍類型，這個非常麻煩，代碼也長，后來，我們將它們移出了ray-class，放在了namespace rt中，但是，仍然放在ray文件中，這個很不合理，所以我們定義了一個RTdef.h，專門用於定義一些光線追蹤的常量和命名

/// RTdef.h

// -----------------------------------------------------
// [author]        lv
// [begin ]        2019.1.1
// [brief ]        the basic concept of rt
// -----------------------------------------------------
#pragma once

#include <lvgm\type_vec\type_vec.h>        //https://www.cnblogs.com/lv-anchoret/p/10163085.html
#include <lvgm\opticsfunc.hpp>            //https://www.cnblogs.com/lv-anchoret/p/10241904.html
#include <lvgm\randfunc.hpp>            //https://www.cnblogs.com/lv-anchoret/p/10241904.html

namespace rt
{
    using rtvar = lvgm::precision;

    using rtvec = lvgm::vec3<rtvar>;

    constexpr static rtvar rtInf() { return static_cast<rtvar>(0x3f3f3f3f); }        //最大值

    constexpr rtvar π = 3.1415926;

}

 

2.光線類

/// ray.h

// -----------------------------------------------------
// [author]        lv
// [begin ]        2018.12
// [brief ]        the ray-class for the ray-tracing project
//                from the 《ray tracing in one week》
// -----------------------------------------------------
#pragma once

#include "RTdef.h"

namespace rt
{

    class ray
    {
    public:
        ray()
            :_a{ rtvec() }
            , _b{ rtvec() }
        {  }

        ray(const rtvec& a, const rtvec& b)
            :_a(a)
            , _b(b)
        {  }

        ray(const ray& r)
            :_a(r._a)
            , _b(r._b)
        {    }

        inline rtvec origin()const { return _a; }

        inline rtvec direction()const { return _b; }

        inline rtvec go(const rtvar t)const { return _a + t * _b; }

    private:
        rtvec _a;

        rtvec _b;

    };
}

 

3.相機類

 

/// camera.h
//https://www.cnblogs.com/lv-anchoret/p/10221058.html
// -----------------------------------------------------
// [author]        lv
// [begin ]        2019.1
// [brief ]        the camera-class for the ray-tracing project
//                from the 《ray tracing in one week》
// -----------------------------------------------------

#pragma once

#include "ray.h"

namespace rt
{

class camera
    {
public:
    camera(rtvec lookfrom, rtvec lookat, rtvec vup, rtvar vfov, rtvar aspect, rtvar aperture, rtvar focus)
        :_eye(lookfrom)
        , _lens_radius(aperture / 2)
    {
        rtvar theta = vfov * π / 180;
        rtvar half_height = tan(theta / 2) * focus;        //tan(theta/2) = (height/2) / 焦距
        rtvar half_width = aspect * half_height;
        _w = (lookfrom - lookat).ret_unitization();
        _u = cross(vup, _w).ret_unitization();
        _v = cross(_w, _u);

        //向量運算
        _start = _eye - half_width * _u - half_height * _v - focus * _w;//高和寬都乘了焦距，w也要乘，不然公式是錯的
        _horizontal = 2 * half_width * _u;
        _vertical = 2 * half_height * _v;
    }

    const ray get_ray(const rtvar u, const rtvar v)const
    {
        rtvec rd = rtvec(_lens_radius * lvgm::random_unit_plane());
        rtvec offset = _u * rd.x() + _v * rd.y();
        return ray{ _eye + offset, _start + u*_horizontal + v*_vertical - (_eye + offset) };
    }

    const ray get_ray(const lvgm::vec2<rtvar>& para)const    {    return get_ray(para.u(), para.v());    }

    inline const rtvec& eye()const { return _eye; }

    inline const rtvec& start()const { return _start; }

    inline const rtvec& horizontal()const { return _horizontal; }

    inline const rtvec& vertical()const { return _vertical; }

    inline const rtvec& u()const { return _u; }

    inline const rtvec& v()const { return _v; }

    inline const rtvec& w()const { return _w; }

    inline const rtvar lens_r()const { return _lens_radius; }

private:
    rtvec _u;

    rtvec _v;

    rtvec _w;

    rtvec _eye;

    rtvec _start;        //left-bottom

    rtvec _horizontal;

    rtvec _vertical;

    rtvar _lens_radius;  //the radius of lens

    };

}

 

 

4.碰撞相交部分

有一個碰撞相交基類

 

/// intersect.h
//https://www.cnblogs.com/lv-anchoret/p/10190092.html
// -----------------------------------------------------
// [author]        lv
// [begin ]        2018.12
// [brief ]        the intersect-class for the ray-tracing project
//                from the 《ray tracing in one week》
// -----------------------------------------------------
#pragma once

namespace rt
{
    class material;

struct hitInfo
    {
    lvgm::precision _t;        //ray 中的系數t
    rtvec _p;                //相交點、撞擊點
    rtvec _n;                //_p點的表面法線
    material* materialp;    //材質
    };

class intersect
    {
public:
    intersect() {  }

    /*
    @brief: 撞擊函數，求取撞擊點相關記錄信息
    @param: sight->視線
    系數t的上下界->篩選撞擊點
    rec->返回撞擊點信息
    @retur: 是否存在合法撞擊點
    */
    virtual bool hit(const ray& sight, rtvar t_min, rtvar t_max, hitInfo& rec)const = 0;

    virtual ~intersect() {  }
    };

}

 

 

 

后面有一個子類intersections是用於處理一組碰撞相交的類，類比於容器

/// intersections.h
//    https://www.cnblogs.com/lv-anchoret/p/10190092.html

// -----------------------------------------------------
// [author]        lv
// [begin ]        2018.12
// [brief ]        the intersections-class for the ray-tracing project
//                from the 《ray tracing in one week》
// -----------------------------------------------------
#pragma once

namespace rt
{

class intersections :public intersect
    {
public:
    intersections() {  }
        
    intersections(intersect** list, size_t n) :_list(list), _size(n) {  }
        
    virtual bool hit(const ray& sight, rtvar t_min, rtvar t_max, hitInfo& rec)const override;

private:
    intersect** _list;

    size_t _size;
    };


bool intersections::hit(const ray& sight, rtvar t_min, rtvar t_max, hitInfo& rec)const
{
    hitInfo t_rec;
    bool hitSomething = false;
    rtvar far = t_max;            //剛開始可以看到無限遠
    for (int i = 0; i < _size; ++i)
    {
        if (_list[i]->hit(sight, t_min, far, t_rec))
        {
            hitSomething = true;
            far = t_rec._t;            //將上一次的最近撞擊點作為視線可達最遠處
            rec = t_rec;
        }
    }
    return hitSomething;
}


}

 

還有一個子類sphere是一種幾何體用來做自身的碰撞檢測的，之后，我們可能還會加入心形幾何體類

/// sphere.h
//  https://www.cnblogs.com/lv-anchoret/p/10190092.html
// -----------------------------------------------------
// [author]        lv
// [begin ]        2018.1.1
// [brief ]        the sphere-class for the ray-tracing project
//                from the 《ray tracing in one week》
// -----------------------------------------------------
#pragma once

namespace rt
{

class sphere :public intersect
    {
public:
    sphere() {  }

        /*
        @para1: 球心坐標
        @para2: 球半徑
        @para3: 材質
        */
    sphere(const rtvec& h, rtvar r, material* ma) :_heart(h), _radius(r), _materialp(ma) {  } 

    ~sphere() { if (_materialp)    delete _materialp; }
        
    virtual bool hit(const ray& sight, rtvar t_min, rtvar t_max, hitInfo& rec)const override;

    inline const rtvar r()const            { return _radius;    }

    inline const rtvec& heart()const    { return _heart;    }

    inline rtvar& r()                    { return _radius;    }

    inline rtvec& heart()                { return _heart;    }

private:
    rtvec _heart;

    rtvar _radius;

    material* _materialp;
    };



bool sphere::hit(const ray& sight, rtvar t_min, rtvar t_max, hitInfo& rec)const
{
    rtvec trace = sight.origin() - _heart;
    rtvar a = dot(sight.direction(), sight.direction());
    rtvar b = 2.0 * dot(trace, sight.direction());
    rtvar c = dot(trace, trace) - _radius * _radius;
    rtvar delt = b*b - 4.0*a*c;
    if (delt > 0)
    {
        rec.materialp = _materialp;
        rtvar x = (-b - sqrt(delt)) / (2.0*a);
        if (x < t_max && x > t_min)
        {
            rec._t = x;
            rec._p = sight.go(rec._t);
            rec._n = (rec._p - _heart) / _radius;
            return true;
        }
        x = (-b + sqrt(delt)) / (2.0*a);
        if (x < t_max && x > t_min)
        {
            rec._t = x;
            rec._p = sight.go(x);
            rec._n = (rec._p - _heart) / _radius;
            return true;
        }
    }
    return false;
}

}

 

一個總文件

/// RThit.h
//    https://www.cnblogs.com/lv-anchoret/p/10190092.html

// -----------------------------------------------------
// [author]        lv
// [begin ]        2019.1
// [brief ]        some intersects
//                intersections
//                sphere
//                heart
// -----------------------------------------------------

#pragma once

#include "ray.h"
#include "intersect.h"

#include "sphere.hpp"
#include "intersections.hpp"

 

5.材質類

材質有一個基類和三個子類

/// material.h

// -----------------------------------------------------
// [author]        lv
// [begin ]        2018.12
// [brief ]        the material-class for the ray-tracing project
//                from the 《ray tracing in one week》
// -----------------------------------------------------
#pragma once

namespace rt
{

//abstract basic class
class material
    {
public:

    /*
    @brief: produce a scattered ray
    @param: InRay -> Incident light
            info -> the information of intersect-point(hit-point)
            attenuation -> when scattered, how much the ray should be attenuated by tis reflectance R
            scattered -> as we talk, it is a new sight; or
                         it is the scattered ray with the intersect-point
    @retur: the function calculate a scattered ray or not
    */
    virtual bool scatter(const ray& InRay, const hitInfo& info, rtvec& attenuation, ray& scattered)const = 0;

    };

}

 

/// diffuse.hpp
// https://www.cnblogs.com/lv-anchoret/p/10198423.html

// -----------------------------------------------------
// [author]        lv
// [begin ]        2018.12
// [brief ]        one of the materials
// -----------------------------------------------------

#pragma once

namespace rt
{
//diffuse material
class lambertian : public material
    {
public:
    lambertian(const rtvec& a) :_albedo(a) {  }

    bool scatter(const ray& rIn, const hitInfo& info, rtvec& attenuation, ray& scattered)const override
    {
        rtvec target = info._p + info._n + lvgm::random_unit_sphere();
        scattered = ray{ info._p, target - info._p };
        attenuation = _albedo;
        return true;
    }
protected:

    rtvec _albedo;
    };

}

 

/// metal.hpp
// https://www.cnblogs.com/lv-anchoret/p/10206773.html

// -----------------------------------------------------
// [author]        lv
// [begin ]        2018.12
// [brief ]        one of the materials
// -----------------------------------------------------

#pragma once

namespace rt
{
//metal material
class metal :public material
    {
public:

    metal(const rtvec& a, const rtvar f = 0.) :_albedo(a) 
        { 
        if (f < 1 && f >= 0)_fuzz = f;
        else _fuzz = 1;
        }
    
    virtual bool scatter(const ray& rIn, const hitInfo& info, rtvec& attenuation, ray& scattered)const
    {
        rtvec target = reflect(rIn.direction().ret_unitization(), info._n);
        scattered = ray{ info._p, target + _fuzz * lvgm::random_unit_sphere() };
        attenuation = _albedo;
        return dot(scattered.direction(), info._n) != 0;
    }

    inline static rtvec reflect(const rtvec& in, const rtvec& n) { return in - 2 * dot(in, n)*n; }
    
protected:

    rtvec _albedo;

    rtvar _fuzz;
    };

}

 

 

/// dielectric.hpp
// https://www.cnblogs.com/lv-anchoret/p/10217719.html

// -----------------------------------------------------
// [author]        lv
// [begin ]        2019.1
// [brief ]        one of the materials
// -----------------------------------------------------
#pragma once

namespace rt
{
    class dielectric :public material
    {
    public:
        dielectric(const rtvar RI) :_RI(RI) {  }

        virtual bool scatter(const ray& InRay, const hitInfo& info, rtvec& attenuation, ray& scattered)const override;

    protected:
        rtvar _RI;

        inline rtvar schlick(const rtvar cosine)const;
    };
    


    bool dielectric::scatter(const ray& InRay, const hitInfo& info, rtvec& attenuation, ray& scattered)const
    {
        rtvec outward_normal;
        rtvec refracted;
        rtvec reflected = reflect(InRay.direction(), info._n);
        rtvar eta;
        rtvar reflect_prob;
        rtvar cos;
        attenuation = rtvec(1., 1., 1.);

        if (dot(InRay.direction(), info._n) > 0)
        {
            outward_normal = -info._n;
            eta = _RI;
            cos = _RI * dot(InRay.direction(), info._n) / InRay.direction().normal();
        }
        else
        {
            outward_normal = info._n;
            eta = 1.0 / _RI;
            cos = -dot(InRay.direction(), info._n) / InRay.direction().normal();
        }

        if (refract(InRay.direction(), outward_normal, eta, refracted))
            reflect_prob = schlick(cos);    //如果有折射，計算反射系數
        else
            reflect_prob = 1.0;        //如果沒有折射，那么為全反射

        if (lvgm::rand01() < reflect_prob)
            scattered = ray(info._p, reflected);
        else
            scattered = ray(info._p, refracted);

        return true;
    }

    inline rtvar dielectric::schlick(const rtvar cosine)const
    {
        rtvar r0 = (1. - _RI) / (1. + _RI);
        r0 *= r0;
        return r0 + (1 - r0)*pow((1 - cosine), 5);
    }
}

 

總文件

/// RTmaterial.h

// -----------------------------------------------------
// [author]        lv
// [begin ]        2019.1
// [brief ]        some materials
//                diffuse
//                metal
//                dielectric
// -----------------------------------------------------
#pragma once

#include "ray.h"
#include "intersect.h"
#include "material.h"

#include "diffuse.hpp"
#include "metal.hpp"
#include "dielectric.hpp"

 

我們所有的文件就寫完了

 

12.2封面完結

這個圖讓我學會了分段渲染。。。

這個圖非常好看，於是乎，整了一個600*400的，整整渲染了兩天（....），內心是崩潰的

我試過並發編程，結果效果不好（自己也不怎么會上鎖。。。）

所以，就只能單線程處理，時間超過十個小時左右吧，VS那個時間過程診斷框就壞死了。。。

有時候，不能一直渲染，這個時候，被迫結束后，只需要讀取已有文件的行數，然后計算出渲染了多少個點了，然后在渲染的雙重for循環中從下一個點開始渲染寫入文件即可，就可以隨時隨地想停就停，想渲染就渲染，因為圖像本事就是一個一個像素點，我們只需要24w個點的文件數據即可，你也可以並發寫入多個文件，最后拼在一起

 

我們采用的相機參數是這樣的

據說是官方的，我也不清楚

還有一個文章寫得非常好，是寫相機的參數測試的，大家可以閱讀一下，對相機的參數有一個更直觀深入的了解

相機各個參數測試效果

 

因為這個圖實在是渲染了好久，所以也沒有出一些其他的效果圖，可能之后會更，大家可以自己設置球體以及相機，歡迎在評論區發出你的渲染圖~

 

下面是代碼：

#define LOWPRECISION

#include <fstream>
#include "RTmaterial.h"
#include "RThit.h"
#include "camera.h"
#define stds std::
using namespace rt;

rtvec lerp(const ray& sight, intersect* world, int depth)
{
    hitInfo info;
    if (world->hit(sight, (rtvar)0.001, rtInf(), info))
    {
        ray scattered;
        rtvec attenuation;
        if (depth < 50 && info.materialp->scatter(sight, info, attenuation, scattered))
            return attenuation * lerp(scattered, world, depth + 1);
        else
            return rtvec(0, 0, 0);
    }
    else
    {
        rtvec unit_dir = sight.direction().ret_unitization();
        rtvar t = 0.5*(unit_dir.y() + 1.);
        return (1. - t)*rtvec(1., 1., 1.) + t*rtvec(0.5, 0.7, 1.0);
    }
}

intersect* random_sphere()
{
    int cnt = 500;
    intersect **list = new intersect*[cnt + 1];
    list[0] = new sphere(rtvec(0, -1000, 0), 1000, new lambertian(rtvec(0.5, 0.5, 0.5)));
    int size = 1;
    for (int a = -11; a < 11; ++a)
        for (int b = -11; b < 11; ++b)
        {
            rtvar choose_mat = lvgm::rand01();
            rtvec center(a + 0.9 * lvgm::rand01(), 0.2, b + 0.9*lvgm::rand01());
            if ((center - rtvec(4, 0.2, 0)).normal()>0.9)
            {
                if (choose_mat < 0.75)
                {
                    list[size++] = new sphere(center, 0.2, new lambertian(rtvec(lvgm::rand01()*lvgm::rand01(), lvgm::rand01()*lvgm::rand01(), lvgm::rand01()*lvgm::rand01())));
                }
                else if (choose_mat < 0.9)
                {
                    list[size++] = new sphere(center, 0.2, new metal(rtvec(0.5*(1 + lvgm::rand01()), 0.5*(1 + lvgm::rand01()), 0.5*(1 + lvgm::rand01())), 0.5*lvgm::rand01()));
                }
                else
                {
                    list[size++] = new sphere(center, 0.2, new dielectric(1.5));
                }
            }
        }
    
    list[size++] = new sphere(rtvec(0, 1, 0), 1.0, new dielectric(1.5));
    list[size++] = new sphere(rtvec(-4, 1, 0), 1.0, new lambertian(rtvec(0.4, 0.2, 0.1)));
    list[size++] = new sphere(rtvec(4, 1, 0), 1.0, new metal(rtvec(0.7, 0.6, 0.5), 0.));

    return new intersections(list, size);
}

void build_12_1()
{
    stds ofstream file("graph12-1.ppm");
    size_t W = 200, H = 120, sample = 100;

    if (file.is_open())
    {
        file << "P3\n" << W << " " << H << "\n255\n" << stds endl;

        intersect* world = random_sphere();

        rtvec lookfrom(13, 2, 3);
        rtvec lookat(0, 0, 0);
        float dist_to_focus = (lookfrom - lookat).normal();
        float aperture = 0.0;
        camera cma(lookfrom, lookat, rtvec(0, 1, 0), 20, rtvar(W) / rtvar(H), aperture, 0.7*dist_to_focus);

        for (int y = H - 1; y >= 0; --y)
            for (int x = 0; x < W; ++x)
            {
                rtvec color;
                for (int cnt = 0; cnt < sample; ++cnt)
                {
                    lvgm::vec2<rtvar> para{
                        (lvgm::rand01() + x) / W,
                        (lvgm::rand01() + y) / H };
                    color += lerp(cma.get_ray(para), world, 0);
                }
                color /= sample;
                color = rtvec(sqrt(color.r()), sqrt(color.g()), sqrt(color.b()));    //gamma 校正
                int r = int(255.99 * color.r());
                int g = int(255.99 * color.g());
                int b = int(255.99 * color.b());
                file << r << " " << g << " " << b << stds endl;
            }
        file.close();

        if (world)delete world;

        stds cout << "complished" << stds endl;
    }
    else
        stds cerr << "open file error" << stds endl;
}


int main()
{
    build_12_1();
}

 

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