aclib20 のバックアップ(No.1)

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- 1 (2020-09-23 (水) 23:49:48)
- 2 (2020-09-24 (木) 09:09:54)
aclib #20 - kray.c の紹介ページ

(by K, 2020.09.23)
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(1) 基本情報

krayは、Kがaclライブラリのデモのために用意したプログラムです。
オリジナルは https://gist.github.com/yhara/ea0e66e0d8bdd114d2401dd133539fa3 です。
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(2) 実行画面

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(3) ソースコード

#include <acl.c>

#define EPS		1.0e-4

typedef struct Vec_ {
	double x, y, z;
} Vec;

Vec Vec_new(double x, double y, double z)
{
	Vec v;
	v.x = x;
	v.y = y;
	v.z = z;
	return v;
}

double Util_clamp(double t, double min, double max)
{
	if (t < min) t = min;
	if (t > max) t = max;
	return t;
}

Vec Vec_add(Vec a, Vec b)    { return Vec_new(a.x + b.x, a.y + b.y, a.z + b.z); }
Vec Vec_sub(Vec a, Vec b)    { return Vec_new(a.x - b.x, a.y - b.y, a.z - b.z); }
Vec Vec_mul(double t, Vec v) { return Vec_new(t * v.x,   t * v.y,   t * v.z);   }
Vec Vec_multi(Vec a, Vec b)  { return Vec_new(a.x * b.x, a.y * b.y, a.z * b.z); }
double Vec_dot(Vec a, Vec b) { return a.x * b.x + a.y * b.y + a.z * b.z;        }
double Vec_length(Vec v)     { return sqrt(Vec_dot(v, v));                      }
Vec Vec_reflect(Vec v, Vec normal) { return Vec_add(v, Vec_mul(-2.0 * Vec_dot(normal, v), normal)); }
AInt32 Util_color(double t) { return (AInt32) (255.99999 * Util_clamp(t, 0.0, 1.0)); }
AInt32 Util_rgb(Vec v) { return aRgb8(Util_color(v.x), Util_color(v.y), Util_color(v.z)); }

Vec Vec_normalize(Vec v)
{
	double len = Vec_length(v);
	if (len > 1.0e-17)
		v = Vec_mul(1.0 / len, v);
	return v;
}

typedef struct Ray_ {
	Vec origin, dir;
} Ray;

Ray Ray_new(Vec origin, Vec dir)
{
	Ray r;
	r.origin = origin;
	r.dir = dir;
	return r;
}

typedef struct Isect_ {
	Vec hit_point, normal, color, ray_dir;
	double distance;
} Isect;

Isect Isect_new(Vec hit_point, Vec normal, Vec color, double distance, Vec ray_dir)
{
	Isect i;
	i.hit_point = hit_point;
	i.normal = normal;
	i.color = color;
	i.distance = distance;
	i.ray_dir = ray_dir;
	return i;
}

double Util_mod2(double t)
{
	t -= (AInt32) (t * (1.0 / 2.0)) * 2.0;
	if (t < 0.0)
		t += 2.0;
	return t;
}

typedef struct Sphere_ {
	double radius;
	Vec position, color;
} Sphere;

Sphere Sphere_new(double radius, Vec position, Vec color)
{
	Sphere s;
	s.radius = radius;
	s.position = position;
	s.color = color;
	return s;
}

void Sphere_intersect(Sphere s, Ray ray, Vec light, Isect *i)
{
	Vec rs = Vec_sub(ray.origin, s.position);
	double b = Vec_dot(rs, ray.dir);
	double c = Vec_dot(rs, rs) - s.radius * s.radius;
	double d = b * b - c;
	if (d < 0.0) return;
	double t = - b - sqrt(d);
	if (t < EPS || t > i->distance) return;
	i->hit_point = Vec_add(ray.origin, Vec_mul(t, ray.dir));
	i->normal = Vec_normalize(Vec_sub(i->hit_point, s.position));
	i->color = Vec_mul(Util_clamp(Vec_dot(light, i->normal), 0.1, 1.0), s.color);
	i->distance = t;
	i->ray_dir = ray.dir;
}

typedef struct Plane_ {
	Vec position, normal, color;
} Plane;

Plane Plane_new(Vec position, Vec normal, Vec color)
{
	Plane p;
	p.position = position;
	p.normal = normal;
	p.color = color;
	return p;
}

void Plane_intersect(Plane p, Ray ray, Vec light, Isect *i)
{
	double d = - Vec_dot(p.position, p.normal);
	double v = Vec_dot(ray.dir, p.normal);
	if (v * v < 1.0e-30) return;
	double t = - (Vec_dot(ray.origin, p.normal) + d) / v;
	if (t < EPS || t > i->distance) return;
	i->hit_point = Vec_add(ray.origin, Vec_mul(t, ray.dir));
	i->normal = p.normal;
	double d2 = Util_clamp(Vec_dot(light, i->normal), 0.1, 1.0);
	if ((Util_mod2(i->hit_point.x) - 1.0) * (Util_mod2(i->hit_point.z) - 1.0) > 0.0)
		d2 *= 0.5;
	i->color = Vec_mul(d2 * (1.0 - Util_clamp(fabs(i->hit_point.z) * 0.04, 0.0, 1.0)), p.color);
	i->distance = t;
	i->ray_dir = ray.dir;
}

typedef struct Util_ {
	Vec light;
	Sphere s1, s2, s3;
	Plane p;
} Util;

void Util_intersect(Util u, Ray ray, Isect *i)
{
	i->distance = 1.0e+30;
	Sphere_intersect(u.s1, ray, u.light, i);
	Sphere_intersect(u.s2, ray, u.light, i);
	Sphere_intersect(u.s3, ray, u.light, i);
	Plane_intersect (u.p,  ray, u.light, i);
}

void aMain()
{
	Util u;
	Isect i;
	u.light = Vec_new(0.577, 0.577, 0.577);
	u.s1 = Sphere_new(0.5, Vec_new( 0.0, -0.5, 0.0),       Vec_new(1.0, 0.0, 0.0));
	u.s2 = Sphere_new(1.0, Vec_new( 2.0,  0.0, cos(6.66)), Vec_new(0.0, 1.0, 0.0));
	u.s3 = Sphere_new(1.5, Vec_new(-2.0,  0.5, cos(3.33)), Vec_new(0.0, 0.0, 1.0));
	u.p  = Plane_new(Vec_new(0.0, -1.0, 0.0), Vec_new(0.0, 1.0, 0.0), Vec_new(1.0, 1.0, 1.0));
	AWindow *win = aOpenWin(512, 384, "kray", 1);
	AInt16 ix, iy;
	for (iy = 0; iy < 384; iy++) {
		for (ix = 0; ix < 512; ix++) {
			double x = ix * (1.0 / 256.0) - 1.0;
			double y = (384 - iy) * (1.0 / 256.0) - 1.0;
			Ray ray = Ray_new(Vec_new(0.0, 2.0, 6.0), Vec_normalize(Vec_new(x, y, -1.0)));
			Util_intersect(u, ray, &i);
			Vec dest_col = Vec_mul(ray.dir.y, Vec_new(1.0, 1.0, 1.0));
			if (i.distance < 1.0e+30) {
				Vec temp_col = dest_col = i.color;
				AInt8 j;
				for (j = 1; j < 4; j++) {
					Ray q = Ray_new(Vec_add(i.hit_point, Vec_mul(EPS, i.normal)), Vec_reflect(i.ray_dir, i.normal));
					Util_intersect(u, q, &i);
					if (i.distance >= 1.0e+30) break;
					dest_col = Vec_add(dest_col, Vec_multi(temp_col, i.color));
					temp_col = Vec_multi(temp_col, i.color);
				}
			}
			aSetPix(win, ix, iy, Util_rgb(dest_col));
		}
		aLeapFlushAll(win, 100);
	}
	aWait(-1);
}
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