1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
|
//
// Created by Keuin on 2022/4/12.
//
#ifndef RT_VIEWPORT_H
#define RT_VIEWPORT_H
#include "timer.h"
#include "bitmap.h"
#include "ray.h"
#include "vec.h"
#include "hitlist.h"
#include <cstdlib>
#include <memory>
#include <limits>
#include <vector>
#include <iostream>
#include <cstdint>
#include <random>
// bias context, used for placing sub-pixels
class bias_ctx {
bool enabled; // put all together, eliminating a virtual function call
std::mt19937_64 mt;
std::uniform_real_distribution<double> uni{0.0, 1.0};
public:
bias_ctx(bool enabled, uint64_t seed = 0UL) : enabled(enabled), mt(std::mt19937_64{seed}) {}
void operator()(double &bx, double &by) {
if (enabled) {
bx = uni(mt);
by = uni(mt);
} else {
bx = 0.0;
by = 0.0;
}
}
};
class viewport {
const double half_width, half_height; // viewport size
const vec3d center; // coordinate of the viewport center point
public:
viewport() = delete;
viewport(double width, double height, vec3d viewport_center) :
half_width(width / 2.0), half_height(height / 2.0), center(viewport_center) {}
/**
* Generate the image seen on given viewpoint.
* @param bx bias on x axis (0.0 <= bx < 1.0)
* @param by bias on y axis (0.0 <= by < 1.0)
* @return
*/
bitmap8b render(const hitlist &world, vec3d viewpoint,
uint16_t image_width, uint16_t image_height,
bias_ctx &bias) const {
bitmap8b image{image_width, image_height};
double bx, by;
const auto r = center - viewpoint;
const int img_hw = image_width / 2, img_hh = image_height / 2;
// iterate over every pixel on the image
for (int j = -img_hh + 1; j <= img_hh; ++j) { // axis y, transformation is needed
for (int i = -img_hw; i < img_hw; ++i) { // axis x
bias(bx, by); // get a random bias (bx, by) for sub-pixel sampling
assert(0 <= bx);
assert(0 <= by);
assert(bx < 1.0);
assert(by < 1.0);
const vec3d off{
.x=1.0 * i / img_hw * half_width + bx,
.y=1.0 * j / img_hh * half_height + by,
.z=0.0
}; // offset on screen plane
const auto dir = r + off; // direction vector from camera to current pixel on screen
const ray3d ray{viewpoint, dir}; // from camera to pixel (on the viewport)
const auto pixel = world.color(ray);
image.set(i + img_hw, -j + img_hh, pixel);
}
}
return image;
}
};
#endif //RT_VIEWPORT_H
|
