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这个算法是均匀采样算法，继承于Sampler类。

类声明：

#pragma once
#ifndef __REGULAR_HEADER__
#define __REGULAR_HEADER__
 
#include "sampler.h"
 
class Regular :public Sampler {
public:
    Regular();
    ~Regular();
    Regular(const integer samps);
    Regular(const integer samps, const integer sets);
    Regular(const Regular& reg);
    Regular& operator=(const Regular& reg);
    virtual Sampler* clone() const;
    virtual void generate_samples();
};
#endif　　

类实现：

#include "pch.h"
#include "regular.h"
 
Regular::Regular() :Sampler() {
    generate_samples();
}
 
Regular::~Regular() {}
 
Regular::Regular(const integer samps) : Sampler(samps) {
    generate_samples();
}
 
Regular::Regular(const integer samps, const integer sets) : Sampler(samps, sets) {
    generate_samples();
}
 
Regular::Regular(const Regular& reg) : Sampler(reg) {
    generate_samples();
}
 
Regular& Regular::operator=(const Regular& reg) {
    if (this == &reg)
        return *this;
    Sampler::operator=(reg);
    return *this;
}
 
Sampler* Regular::clone() const {
    return new Regular(*this);
}
 
void Regular::generate_samples() {
    integer n = (integer)std::sqrt((ldouble)nsamples);
    for (integer p = 0; p < nsets; p++) {
        for (integer i=0;i<n;i++)
            for (integer j = 0; j < n; j++) {
                Point2 sp((j + 0.5) / n, (i + 0.5) / n); //均匀采样
                samples.push_back(sp);
            }
    }
}

测试采样算法：

添加Sampler类和采样数到ViewPlane类中，增加函数（若无特殊声明，不再重复修改的部分）

void set_samples(const integer n);

void set_sampler(Sampler* const sp);

ViewPlane类具体声明如下：

#pragma once
#ifndef __VIEWPLANE_HEADER__
#define __VIEWPLANE_HEADER__
 
#include "../../Types.h"
 
class Sampler;
 
class ViewPlane {
public:
    ViewPlane();
    ViewPlane(const ViewPlane& vp);
    void set_hres(const integer hr);
    void set_vres(const integer vr);
    void set_pixelsize(const ldouble ps);
    void set_gamma(const ldouble ga);
    void set_samples(const integer n);//新增
    void set_sampler(Sampler* const sp);//新增
    integer hres;
    integer vres;
    integer nsamples;//新增
    ldouble s;
    ldouble g;
    Sampler* sampler;//新增
};
 
#endif　

需要修改的类成员：

#include "pch.h"
#include "viewplane.h"
#include "../samplers/jittered.h"
 
 
ViewPlane::ViewPlane() :hres(200), vres(100), s(0.02), g(1), nsamples(16), sampler(nullptr) {}
 
ViewPlane::ViewPlane(const ViewPlane& vp) 
    : hres(vp.hres), vres(vp.vres), s(vp.s), g(vp.g), nsamples(vp.nsamples), sampler(vp.sampler) {}
 
...
 
void ViewPlane::set_samples(const integer n) {//和书上不同，剔除特殊性，增加兼容性
    nsamples = n;
    sampler->clear();
    sampler->set_num_samples(nsamples);
    sampler->setup_shuffled_indices();
    sampler->generate_samples();
}
 
void ViewPlane::set_sampler(Sampler* const sp) {
    if (sampler != nullptr) {
        delete sampler;
        sampler = nullptr;
    }
    nsamples = sp->get_num_samples();
    sampler = sp;
}

World类只修改build和render部分：

void World::build() {
    vp.set_hres(200);
    vp.set_vres(100);
    vp.set_sampler(new Regular());//所有采样修改都在这里测试
    tracer_ptr = new MultiSphere(this);
    Geometrics* obj = new Sphere(0, 0.5);
    obj->set_color(RGBColor(1, 0, 0));
    add_object(obj);
    obj = new Sphere(Point3(0, -100.5, 0), 100);
    obj->set_color(RGBColor(0, 0, 1));
    add_object(obj);
}

render部分若无特殊声明，之后不再重复修改部分。

void World::render() {
    Ray ray;
    ldouble x, y;
    open_window(vp.hres, vp.vres);
    Point3 sp;
    ray.o = Point3(0, 0, 1);
    for (integer r = vp.vres - 1; r >= 0; r--)//render from left-corner to right-corner
        for (integer c = 0; c < vp.hres; c++) {
            RGBColor color;
            for (integer p = 0; p < vp.nsamples; p++) {//增加样本
                sp = vp.sampler->sample_unit_square();
                x = vp.s * (c - 0.5 * vp.hres + sp.x);
                y = vp.s * (r - 0.5 * vp.vres + sp.y);
                ray.d = Point3(x, y, -1);
                color += tracer_ptr->trace_ray(ray);
            }
            color /= vp.nsamples;
            display_pixel(r, c, color);
        }
}