MultiJittered采样类定义和测试

多重抖动在书上说的是水平和竖直方面随机交换。

类声明：

#pragma once
#ifndef __MULTIJITTERED_HEADER__
#define __MULTIJITTERED_HEADER__

#include "sampler.h"

class MultiJittered :public Sampler {
public:
	MultiJittered();
	~MultiJittered();
	MultiJittered(const integer samps);
	MultiJittered(const integer samps, const integer sets);
	MultiJittered(const MultiJittered& mji);
	MultiJittered& operator=(const MultiJittered& mji);
	virtual Sampler* clone() const;
	virtual void generate_samples();
private:
	void shuffled_x_coordinates(integer n);//水平抖动
	void shuffled_y_coordinates(integer n);//竖直抖动
	ldouble subcell_width;
};
#endif

类实现：

#include "pch.h"
#include "multijittered.h"

MultiJittered::MultiJittered() :Sampler() {
	generate_samples();
}

MultiJittered::~MultiJittered() {}

MultiJittered::MultiJittered(const integer samps) :Sampler(samps) {
	generate_samples();
}

MultiJittered::MultiJittered(const integer samps, const integer sets) : Sampler(samps, sets) {
	generate_samples();
}

MultiJittered::MultiJittered(const MultiJittered& mji):Sampler(mji) {
	generate_samples();
}

MultiJittered& MultiJittered::operator=(const MultiJittered& mji) {
	if (this == &mji)
		return *this;
	Sampler::operator=(mji);
	return *this;
}

Sampler* MultiJittered::clone() const {
	return new MultiJittered(*this);
}

void MultiJittered::generate_samples() {
	integer n = (integer)std::sqrt((ldouble)nsamples);
	subcell_width = 1.0 / nsamples;
	for (integer i = 0; i < nsamples * nsets; i++)
		samples.push_back(Point3());
	for (integer p = 0; p < nsets; p++)
		for (integer i = 0; i < n; i++)
			for (integer j = 0; j < n; j++) {
				samples[i * n + j + p * nsamples].x = (i * n + j) * subcell_width + random_ldouble(0, subcell_width);
				samples[i * n + j + p * nsamples].y = (j * n + i) * subcell_width + random_ldouble(0, subcell_width);
			}
	shuffled_x_coordinates(n);
	shuffled_y_coordinates(n);
}

void MultiJittered::shuffled_x_coordinates(integer n) {
	for (integer p = 0; p < nsets; p++) {
		for (integer i = 0; i < n; i++)
			for (integer j = 0; j < n; j++) {
				integer k = random_integer(j, n - 1);
				std::swap(samples[i * n + j + p * nsamples].x, samples[i * n + k + p * nsamples].x);
			}
	}
}

void MultiJittered::shuffled_y_coordinates(integer n) {
	for (integer p = 0; p < nsets; p++) {
		for (integer i = 0; i < n; i++)
			for (integer j = 0; j < n; j++) {
				integer k = random_integer(j, n - 1);
				std::swap(samples[j * n + i + p * nsamples].y, samples[k * n + i + p * nsamples].y);
			}
	}
}

测试结果图：