* aclib #20 - kray.c の紹介ページ
-(by [[K]], 2020.09.23)
** (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。
** (2) 実行画面
-http://k.osask.jp/files/pic20200923a.png
** (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;
Vec v = { x, y, 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;
Vec hit_point, normal, color;
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;
typedef struct Object_ {
Vec pos, col, nor;
double rad; // radius
} Object; // Sphere(pos, col, rad) or Plane(pos, col, nor).
Sphere Sphere_new(double radius, Vec position, Vec color)
void Sphere_intersect(Object s, Vec ray_origin, Vec ray_dir, Vec light, Isect *i)
{
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;
Vec rs = Vec_sub(ray_origin, s.pos);
double b = Vec_dot(rs, ray_dir);
double c = Vec_dot(rs, rs) - s.rad * s.rad;
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->hit_point = Vec_add(ray_origin, Vec_mul(t, ray_dir));
i->normal = Vec_normalize(Vec_sub(i->hit_point, s.pos));
i->color = Vec_mul(Util_clamp(Vec_dot(light, i->normal), 0.1, 1.0), s.col);
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)
void Plane_intersect(Object p, Vec ray_origin, Vec ray_dir, Vec light, Isect *i)
{
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);
double d = - Vec_dot(p.pos, p.nor);
double v = Vec_dot(ray_dir, p.nor);
if (v * v < 1.0e-30) return;
double t = - (Vec_dot(ray.origin, p.normal) + d) / v;
double t = - (Vec_dot(ray_origin, p.nor) + 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;
i->hit_point = Vec_add(ray_origin, Vec_mul(t, ray_dir));
i->normal = p.nor;
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->color = Vec_mul(d2 * (1.0 - Util_clamp(fabs(i->hit_point.z) * 0.04, 0.0, 1.0)), p.col);
i->distance = t;
i->ray_dir = ray.dir;
}
typedef struct Util_ {
Vec light;
Sphere s1, s2, s3;
Plane p;
Object s1, s2, s3, p;
} Util;
void Util_intersect(Util u, Ray ray, Isect *i)
void Util_intersect(Util u, Vec ray_origin, Vec ray_dir, 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);
Sphere_intersect(u.s1, ray_origin, ray_dir, u.light, i);
Sphere_intersect(u.s2, ray_origin, ray_dir, u.light, i);
Sphere_intersect(u.s3, ray_origin, ray_dir, u.light, i);
Plane_intersect (u.p, ray_origin, ray_dir, 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));
u.s1.rad = 0.5; u.s1.pos = Vec_new( 0.0, -0.5, 0.0); u.s1.col = Vec_new(1.0, 0.0, 0.0);
u.s2.rad = 1.0; u.s2.pos = Vec_new( 2.0, 0.0, cos(6.66)); u.s2.col = Vec_new(0.0, 1.0, 0.0);
u.s3.rad = 1.5; u.s3.pos = Vec_new(-2.0, 0.5, cos(3.33)); u.s3.col = Vec_new(0.0, 0.0, 1.0);
u.p.pos = Vec_new(0.0, -1.0, 0.0); u.p.nor = Vec_new(0.0, 1.0, 0.0); u.p.col = Vec_new(1.0, 1.0, 1.0);
AWindow *win = aOpenWin(512, 384, "kray", 1);
AInt16 ix, iy;
AInt16 ix, iy, j;
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));
Vec ray_dir = Vec_normalize(Vec_new(x, y, -1.0));
Util_intersect(u, Vec_new(0.0, 2.0, 6.0), ray_dir, &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(i.hit_point, Vec_reflect(i.ray_dir, i.normal));
Util_intersect(u, q, &i);
ray_dir = Vec_reflect(ray_dir, i.normal);
Util_intersect(u, i.hit_point, ray_dir, &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);
dest_col = Vec_add(dest_col, temp_col);
}
}
aSetPix(win, ix, iy, Util_rgb(dest_col));
}
aLeapFlushAll(win, 100);
}
aWait(-1);
}
** (4) 備考
-構造体を引数に渡すとき、ポインタ渡しにしていないので、おそらく無駄なコピーが発生し、速度的には不利だろうと思われます。
-しかしその辺をきちんと書くと、行数が数十行増えてしまうので、あえてこの書き方にしています。
-mandel.cと比べればそれほど遅くはないので、まあこれでもいいかなと思っています。
* こめんと欄
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