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raycaster.c
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raycaster.c
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#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <math.h>
// pixel struct
typedef struct Pixel{
unsigned char red;
unsigned char green;
unsigned char blue;
} Pixel;
// object struct
typedef struct {
int kind;
double color[3];
union {
struct {
double width;
double height;
} camera;
struct {
double position[3];
double radius;
} sphere;
struct {
double position[3];
double normal[3];
} plane;
};
} Object;
// plane intersection
double plane_intersection(double* Ro, double* Rd, double* C, double* N) {
double subtract[3];
subtract[0] = C[0]-Ro[0];
subtract[1] = C[1]-Ro[1];
subtract[2] = C[2]-Ro[2];
double dot1 = N[0]*subtract[0] + N[1]*subtract[1] + N[2]*subtract[2];
double dot2 = N[0]*Rd[0] + N[1]*Rd[1] + N[2]*Rd[2];
return dot1/dot2;
}
// square root
static inline double sqr(double v) {
return v*v;
}
// sphere intersection
double sphere_intersection(double* Ro, double* Rd, double* C, double r) {
double a = (sqr(Rd[0]) + sqr(Rd[1]) + sqr(Rd[2]));
double b = (2*(Ro[0]*Rd[0] - Rd[0]*C[0] + Ro[1]*Rd[1] - Rd[1]*C[1] + Ro[2]*Rd[2] - Rd[2]*C[2]));
double c = sqr(Ro[0]) - 2*Ro[0]*C[0] + sqr(C[0]) + Ro[1] - 2*Ro[1]*C[1] + sqr(C[1]) + sqr(Ro[2]) - 2*Ro[2]*C[2] + sqr(C[2]) - sqr(r);
double det = sqr(b) - 4 * a * c;
if (det < 0) return -1;
det = sqrt(det);
double t0 = (-b - det) / (2*a);
if (t0 > 0) return t0;
double t1 = (-b + det) / (2*a);
if (t1 > 0) return t1;
return -1;
}
// object array
Object* object_array[128];
int obj = 0;
int line = 1;
// next char function
int next_c(FILE* json) {
int c = fgetc(json);
#ifdef DEBUG
printf("next_c: '%c'\n", c);
#endif
if (c == '\n') {
line += 1;
}
if (c == EOF) {
fprintf(stderr, "Error: Unexpected end of file on line number %d.\n", line);
exit(1);
}
return c;
}
// expect error
void expect_c(FILE* json, int d) {
int c = next_c(json);
if (c == d) return;
fprintf(stderr, "Error: Expected '%c' on line %d.\n", d, line);
exit(1);
}
// skip whitespace
void skip_ws(FILE* json) {
int c = next_c(json);
while (isspace(c)) {
c = next_c(json);
}
ungetc(c, json);
}
// next string
char* next_string(FILE* json) {
char buffer[129];
int c = next_c(json);
if (c != '"') {
fprintf(stderr, "Error: Expected string on line %d.\n", line);
exit(1);
}
c = next_c(json);
int i = 0;
while (c != '"') {
if (i >= 128) {
fprintf(stderr, "Error: Strings longer than 128 characters in length are not supported.\n");
exit(1);
}
if (c == '\\') {
fprintf(stderr, "Error: Strings with escape codes are not supported.\n");
exit(1);
}
if (c < 32 || c > 126) {
fprintf(stderr, "Error: Strings may contain only ascii characters.\n");
exit(1);
}
buffer[i] = c;
i += 1;
c = next_c(json);
}
buffer[i] = 0;
return strdup(buffer);
}
// next number
double next_number(FILE* json) {
double value;
fscanf(json, "%lf", &value);
return value;
}
// next vector
double* next_vector(FILE* json) {
double* v = malloc(3*sizeof(double));
expect_c(json, '[');
skip_ws(json);
v[0] = next_number(json);
skip_ws(json);
expect_c(json, ',');
skip_ws(json);
v[1] = next_number(json);
skip_ws(json);
expect_c(json, ',');
skip_ws(json);
v[2] = next_number(json);
skip_ws(json);
expect_c(json, ']');
return v;
}
// read scene
void read_scene(char* filename) {
int c;
FILE* json = fopen(filename, "r");
if (json == NULL) {
fprintf(stderr, "Error: Could not open file \"%s\"\n", filename);
exit(1);
}
skip_ws(json);
expect_c(json, '[');
skip_ws(json);
while (1) {
c = fgetc(json);
if (c == ']') {
fprintf(stderr, "Error: This is the worst scene file EVER.\n");
fclose(json);
return;
}
if (c == '{') {
skip_ws(json);
char* key = next_string(json);
if (strcmp(key, "type") != 0) {
fprintf(stderr, "Error: Expected \"type\" key on line number %d.\n", line);
exit(1);
}
skip_ws(json);
expect_c(json, ':');
skip_ws(json);
char* value = next_string(json);
object_array[obj] = malloc(sizeof(Object));
Object new;
if (strcmp(value, "camera") == 0) {
(*object_array[obj]).kind = 0;
printf("Found camera\n");
} else if (strcmp(value, "sphere") == 0) {
(*object_array[obj]).kind = 1;
printf("Found sphere\n");
} else if (strcmp(value, "plane") == 0) {
(*object_array[obj]).kind = 2;
printf("Found plane\n");
} else {
fprintf(stderr, "Error: Unknown type, \"%s\", on line number %d.\n", value, line);
exit(1);
}
skip_ws(json);
while (1) {
c = next_c(json);
if (c == '}') {
obj++;
break;
} else if (c == ',') {
skip_ws(json);
char* key = next_string(json);
skip_ws(json);
expect_c(json, ':');
skip_ws(json);
if ((strcmp(key, "width") == 0) ||
(strcmp(key, "height") == 0) ||
(strcmp(key, "radius") == 0)) {
double value = next_number(json);
if(strcmp(key, "width") == 0){
if((*object_array[obj]).kind == 0) (*object_array[obj]).camera.width = value;
}
else if(strcmp(key, "height") == 0){
if((*object_array[obj]).kind == 0) (*object_array[obj]).camera.height = value;
}
else if(strcmp(key, "radius") == 0){
(*object_array[obj]).sphere.radius = value;
}
} else if ((strcmp(key, "color") == 0) ||
(strcmp(key, "position") == 0) ||
(strcmp(key, "normal") == 0)) {
double* value = next_vector(json);
if(strcmp(key, "color") == 0){
(*object_array[obj]).color[0] = value[0];
(*object_array[obj]).color[1] = value[1];
(*object_array[obj]).color[2] = value[2];
}
else if(strcmp(key, "position") == 0){
if((*object_array[obj]).kind == 1){
(*object_array[obj]).sphere.position[0] = value[0];
(*object_array[obj]).sphere.position[1] = value[1];
(*object_array[obj]).sphere.position[2] = value[2];
}
else if((*object_array[obj]).kind == 2){
(*object_array[obj]).plane.position[0] = value[0];
(*object_array[obj]).plane.position[1] = value[1];
(*object_array[obj]).plane.position[2] = value[2];
}
}
else if(strcmp(key, "normal") == 0){
(*object_array[obj]).plane.normal[0] = value[0];
(*object_array[obj]).plane.normal[1] = value[1];
(*object_array[obj]).plane.normal[2] = value[2];
}
} else {
fprintf(stderr, "Error: Unknown property, \"%s\", on line %d.\n",
key, line);
}
skip_ws(json);
} else {
fprintf(stderr, "Error: Unexpected value on line %d\n", line);
exit(1);
}
}
skip_ws(json);
c = next_c(json);
if (c == ',') {
skip_ws(json);
} else if (c == ']') {
fclose(json);
object_array[obj] = NULL;
return;
} else {
fprintf(stderr, "Error: Expecting ',' or ']' on line %d.\n", line);
exit(1);
}
}
}
}
// normalize
static inline void normalize(double* v) {
double len = sqrt(sqr(v[0]) + sqr(v[1]) + sqr(v[2]));
v[0] /= len;
v[1] /= len;
v[2] /= len;
}
// main
int main(int argc, char **argv) {
FILE* output;
output = fopen(argv[4], "wb+");
fprintf(output, "P3\n");
fprintf(output, "%d %d\n%d\n", atoi(argv[1]), atoi(argv[2]), 1);
read_scene(argv[3]);
int i = 0;
double w;
double h;
while(1){
if (object_array[i]->kind == 0){
w = object_array[i]->camera.width;
h = object_array[i]->camera.height;
printf("Camera found and variables set.\n");
break;
}
i++;
}
double cx = 0;
double cy = 0;
int M = atoi(argv[2]);
int N = atoi(argv[1]);
double pixheight = h / M;
double pixwidth = w / N;
double* color;
for (int y = M; y > 0; y--) {
for (int x = 0; x < N; x += 1) {
double Ro[3] = {0, 0, 0};
double Rd[3] = {
cx - (w/2) + pixwidth * (x + 0.5),
cy - (h/2) + pixheight * (y + 0.5),
1
};
normalize(Rd);
double best_t = INFINITY;
for (int i=0; object_array[i] != 0; i++) {
double t = 0;
switch(object_array[i]->kind) {
case 0:
break;
case 1:
t = sphere_intersection(Ro, Rd,
object_array[i]->sphere.position,
object_array[i]->sphere.radius);
break;
case 2:
t = plane_intersection(Ro, Rd,
object_array[i]->plane.position,
object_array[i]->plane.normal);
break;
default:
fprintf(stderr, "Error...");
exit(1);
}
if (t > 0 && t < best_t) {
best_t = t;
color = object_array[i]->color;
}
}
Pixel new;
if (best_t > 0 && best_t != INFINITY) {
new.red = color[0];
new.green = color[1];
new.blue = color[2];
fprintf(output, "%i %i %i ", new.red, new.green, new.blue);
} else {
fprintf(output, "0 0 0 ");
}
}
}
fclose(output);
return 0;
}