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#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#define WIDTH 1080
#define HEIGHT 1080
#define BUFFER_SIZE (WIDTH * HEIGHT * 4)
#define LENGTH(array) (sizeof(array) / sizeof(array[0]))
#define MAX(x, y) (x > y ? x : y)
#define MIN(x, y) (x < y ? x : y)
#define POW2(x) ((x) * (x))
#define POW3(x) ((x) * (x) * (x))
#define POW4(x) ((x) * (x) * (x) * (x))
#define POW5(x) ((x) * (x) * (x) * (x) * (x))
typedef struct {
float position[3];
float radius;
float diffuse[3];
} Object;
typedef struct {
float position[3];
float diffuse[3];
} Light;
static Object objects[2] = {{.position={1.5, 0, -20}, .radius=.1, .diffuse={0, 0, .3}},
{.position={-1.5, 0, -30}, .radius=.1, .diffuse={0, 0, .3}}};
static Light lights[1] = {{.position={0, 2, -4}, .diffuse={0, .7, .7}}};
static unsigned char buffer[BUFFER_SIZE];
static float
dot(float x[3], float y[3]) {
return x[0] * y[0] + x[1] * y[1] + x[2] * y[2];
}
static void
normalize(float x[3]) {
float len;
int i;
len = sqrt(dot(x, x));
for(i = 0; i < 3; ++i)
x[i] /= len;
}
static void
trace(float s[3], float d[3], float pixel[3], int N) {
int i, j;
float D;
float l[3];
float n[3];
float t;
float v[3];
float vd, vv;
float y[3];
Object *object = objects;
Light *light = lights;
for(j = 0; j < LENGTH(objects); ++j) {
object = &objects[j];
for(i = 0; i < 3; ++i)
v[i] = s[i] - object->position[i];
vd = dot(v, d);
vv = dot(v, v);
D = POW2(2 * vd) - 4 * (vv - POW2(object->radius));
if(D < 0) {
pixel[0] += .3;
pixel[1] += .15;
pixel[2] += .075;
} else {
t = MIN(-vd + sqrt(D), -vd - sqrt(D));
for(i = 0; i < 3; ++i) {
y[i] = s[i] + t * d[i];
n[i] = y[i] - object->position[i];
l[i] = light->position[i] - object->position[i];
}
normalize(n);
normalize(l);
for(i = 0; i < 3; ++i) {
n[i] = (object->diffuse[i] + light->diffuse[i]) * dot(n, l);
//n[i] = object->diffuse[i];
pixel[i] += n[i];
}
if(N)
trace(y, n, pixel, N - 1);
}
}
}
static void
display(void) {
int i, j;
float x, y;
float s[3] = {0, 0, 1};
float d[3];
float pixel[3];
memset(buffer, '\0', sizeof(buffer));
for(i = 0; i < BUFFER_SIZE; i += 4) {
x = (i / 4) % WIDTH - WIDTH / 2;
y = (i / 4) / WIDTH - HEIGHT / 2;
d[0] = x / (WIDTH / 2);
d[1] = y / (HEIGHT / 2);
d[2] = -1;
memset(pixel, '\0', sizeof(pixel));
trace(s, d, pixel, 0);
//printf("%f %f %f\n", pixel[0], pixel[1], pixel[2]);
for(j = 0; j < 3; ++j)
buffer[i + j] = MIN(255 * pixel[j], 255);
}
glDrawPixels(WIDTH, HEIGHT, GL_BGRA, GL_UNSIGNED_BYTE, buffer);
glutSwapBuffers();
}
static void
reshape(int w, int h) {
glViewport(0, 0, w, h);
}
static void
keyboard(unsigned char key, int x, int y) {
if (key == 27)
exit(0);
}
static int
init(int argc, char **argv, int w, int h) {
glutInit(&argc, argv);
glutInitWindowPosition(0, 0);
glutInitWindowSize(w, h);
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
glutCreateWindow(argv[0]);
glDepthMask(0);
glDisable(GL_DEPTH_TEST);
glDisable(GL_BLEND);
return 0;
}
int
main(int argc, char **argv) {
if (init(argc, argv, WIDTH, HEIGHT))
return 1;
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutKeyboardFunc(keyboard);
glutMainLoop();
return 0;
}
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