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#include<graphics.h>#include<conio.h>#include <math.h> // fminf(), sinf(), cosf(), sqrt()#include <stdlib.h> // rand(), RAND_MAX
#define TWO_PI 6.28318530718f#define W 1024#define H 1024#define N 256#define MAX_STEP 64#define MAX_DISTANCE 2.0f#define EPSILON 1e-6f
typedef struct { float sd, emissive; } Result;
unsigned char img[W * H * 3];
float capsuleSDF(float x, float y, float ax, float ay, float bx, float by, float r) {  float vx = x - ax, vy = y - ay, ux = bx - ax, uy = by - ay;  float t = fmaxf(fminf((vx * ux + vy * uy) / (ux * ux + uy * uy), 1.0f), 0.0f);  float dx = vx - ux * t, dy = vy - uy * t;  return sqrtf(dx * dx + dy * dy) - r;}
Result scene(float x, float y) {  x = fabsf(x - 0.5f) + 0.5f;  Result a = { capsuleSDF(x, y, 0.75f, 0.25f, 0.75f, 0.75f, 0.05f), 1.0f };  Result b = { capsuleSDF(x, y, 0.75f, 0.25f, 0.50f, 0.75f, 0.05f), 1.0f };  return a.sd < b.sd ? a : b;}
float trace(float ox, float oy, float dx, float dy) {  float t = 0.0f;  for (int i = 0; i < MAX_STEP && t < MAX_DISTANCE; i++) {    Result r = scene(ox + dx * t, oy + dy * t);    if (r.sd < EPSILON)      return r.emissive;    t += r.sd;  }  return 0.0f;}
float sample(float x, float y) {  float sum = 0.0f;  for (int i = 0; i < N; i++) {    float a = TWO_PI * (i + (float)rand() / RAND_MAX) / N;    sum += trace(x, y, cosf(a), sinf(a));  }  return sum / N;}
int main() {  initgraph(W, H);  unsigned char* p = img;  for (int y = 0; y < H; y++)  {    for (int x = 0; x < W; x++, p += 3)    {      p[0] = p[1] = p[2] = (int)(fminf(sample((float)x / W, (float)y / H) * 255.0f, 255.0f));      putpixel(x, y, RGB(p[0], p[1], p[2]));    }  }  _getch();}

#include<graphics.h>#include<conio.h>#include <math.h> // fabsf(), fminf(), fmaxf(), sinf(), cosf(), sqrt()#include <stdlib.h> // rand(), RAND_MAX
#define TWO_PI 6.28318530718f#define W 1024#define H 1024#define N 256#define MAX_STEP 64#define MAX_DISTANCE 5.0f#define EPSILON 1e-6f#define BIAS 1e-4f#define MAX_DEPTH 5
typedef struct { float sd, emissive, reflectivity, eta; } Result;
unsigned char img[W * H * 3];
float circleSDF(float x, float y, float cx, float cy, float r) {  float ux = x - cx, uy = y - cy;  return sqrtf(ux * ux + uy * uy) - r;}
float capsuleSDF(float x, float y, float ax, float ay, float bx, float by, float r) {  float vx = x - ax, vy = y - ay, ux = bx - ax, uy = by - ay;  float t = fmaxf(fminf((vx * ux + vy * uy) / (ux * ux + uy * uy), 1.0f), 0.0f);  float dx = vx - ux * t, dy = vy - uy * t;  return sqrtf(dx * dx + dy * dy) - r;}
Result unionOp(Result a, Result b) {  return a.sd < b.sd ? a : b;}
Result scene(float x, float y) {  x = fabsf(x - 0.5f) + 0.5f;  Result a = { capsuleSDF(x, y, 0.75f, 0.25f, 0.75f, 0.75f, 0.05f), 0.0f, 0.2f, 1.5f };  Result b = { capsuleSDF(x, y, 0.75f, 0.25f, 0.50f, 0.75f, 0.05f), 0.0f, 0.2f, 1.5f };  y = fabsf(y - 0.5f) + 0.5f;  Result c = { circleSDF(x, y, 1.05f, 1.05f, 0.05f), 5.0f, 0.0f, 0.0f };  return unionOp(a, unionOp(b, c));}
void gradient(float x, float y, float* nx, float* ny) {  *nx = (scene(x + EPSILON, y).sd - scene(x - EPSILON, y).sd) * (0.5f / EPSILON);  *ny = (scene(x, y + EPSILON).sd - scene(x, y - EPSILON).sd) * (0.5f / EPSILON);}
void reflect(float ix, float iy, float nx, float ny, float* rx, float* ry) {  float idotn2 = (ix * nx + iy * ny) * 2.0f;  *rx = ix - idotn2 * nx;  *ry = iy - idotn2 * ny;}
int refract(float ix, float iy, float nx, float ny, float eta, float* rx, float* ry) {  float idotn = ix * nx + iy * ny;  float k = 1.0f - eta * eta * (1.0f - idotn * idotn);  if (k < 0.0f)    return 0; // Total internal reflection  float a = eta * idotn + sqrtf(k);  *rx = eta * ix - a * nx;  *ry = eta * iy - a * ny;  return 1;}
float trace(float ox, float oy, float dx, float dy, int depth) {  float t = 1e-3f;  float sign = scene(ox, oy).sd > 0.0f ? 1.0f : -1.0f;  for (int i = 0; i < MAX_STEP && t < MAX_DISTANCE; i++) {    float x = ox + dx * t, y = oy + dy * t;    Result r = scene(x, y);    if (r.sd * sign < EPSILON) {      float sum = r.emissive;      if (depth < MAX_DEPTH && (r.reflectivity > 0.0f || r.eta > 0.0f)) {        float nx, ny, rx, ry, refl = r.reflectivity;        gradient(x, y, &nx, &ny);        nx *= sign;        ny *= sign;        if (r.eta > 0.0f) {          if (refract(dx, dy, nx, ny, sign < 0.0f ? r.eta : 1.0f / r.eta, &rx, &ry))            sum += (1.0f - refl) * trace(x - nx * BIAS, y - ny * BIAS, rx, ry, depth + 1);          else            refl = 1.0f; // Total internal reflection        }        if (refl > 0.0f) {          reflect(dx, dy, nx, ny, &rx, &ry);          sum += refl * trace(x + nx * BIAS, y + ny * BIAS, rx, ry, depth + 1);        }      }      return sum;    }    t += r.sd * sign;  }  return 0.0f;}
float sample(float x, float y) {  float sum = 0.0f;  for (int i = 0; i < N; i++) {    float a = TWO_PI * (i + (float)rand() / RAND_MAX) / N;    sum += trace(x, y, cosf(a), sinf(a), 0);  }  return sum / N;}
int main() {  initgraph(W, H);  unsigned char* p = img;  for (int y = 0; y < H; y++)  {    for (int x = 0; x < W; x++, p += 3)    {      p[0] = p[1] = p[2] = (int)(fminf(sample((float)x / W, (float)y / H) * 255.0f, 255.0f));      putpixel(x,y,RGB(p[0],p[1],p[2]));    }  }  _getch();}