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harieamjari/box2.c

Created April 22, 2021 03:07
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box2.c
#include <assert.h> // so I wont have to do error handling
#include <math.h>
#include <png.h> // to output frames as png files
#include <stdio.h> // I/O
#include <stdlib.h>
#include <string.h>
#define FRAMES 50
/* this may be a vertex or a vector */
struct vec3D {
double x, y, z;
};
/* A triangle is composed of 3D vertices */
struct triangle3D {
struct vec3D vertex[3];
};
/* An object is composed of triangles */
struct object3D {
int faces;
struct triangle3D *face;
};
/* A scene is composed of objects */
struct scene3D {
int objects;
struct object3D *object;
};
int width, height;
static double dot_product(const struct vec3D a, const struct vec3D b) {
return a.x * b.x + a.y * b.y + a.z * b.z;
}
static double magnitude(const struct vec3D a) {
return sqrt(dot_product(a, a));
}
static struct object3D translate(const struct object3D ctx, const double dx,
const double dy, const double dz) {
struct triangle3D *face = malloc(sizeof(struct triangle3D) * ctx.faces);
assert(face != NULL);
for (int i = 0; i < ctx.faces; i++) {
face[i] =
(struct triangle3D){.vertex = {[0].x = ctx.face[i].vertex[0].x + dx,
[0].y = ctx.face[i].vertex[0].y + dy,
[0].z = ctx.face[i].vertex[0].z + dz,
[1].x = ctx.face[i].vertex[1].x + dx,
[1].y = ctx.face[i].vertex[1].y + dy,
[1].z = ctx.face[i].vertex[1].z + dz,
[2].x = ctx.face[i].vertex[2].x + dx,
[2].y = ctx.face[i].vertex[2].y + dy,
[2].z = ctx.face[i].vertex[2].z + dz}};
}
return (struct object3D){.faces = ctx.faces, .face = face};
}
static struct object3D rotate(const struct object3D ctx, const double dx,
const double dy, const double dz) {
struct triangle3D *face = malloc(sizeof(struct triangle3D) * ctx.faces);
assert(face != NULL);
for (int i = 0; i < ctx.faces; i++) {
face[i] = (struct triangle3D){
.vertex = {[0].x = cos(dz) * cos(dy) * ctx.face[i].vertex[0].x +
(cos(dz) * sin(dy) * sin(dx) - sin(dz) * cos(dx)) *
ctx.face[i].vertex[0].y +
(cos(dz) * sin(dy) * cos(dx) + sin(dz) * sin(dx)) *
ctx.face[i].vertex[0].z,
[0].y = sin(dz) * cos(dy) * ctx.face[i].vertex[0].x +
(sin(dz) * sin(dy) * sin(dx) + cos(dz) * cos(dx)) *
ctx.face[i].vertex[0].y +
(sin(dz) * sin(dy) * cos(dx) - cos(dz) * sin(dx)) *
ctx.face[i].vertex[0].z,
[0].z = -sin(dy) * ctx.face[i].vertex[0].x +
cos(dy) * sin(dx) * ctx.face[i].vertex[0].y +
cos(dy) * cos(dx) * ctx.face[i].vertex[0].z,
[1].x = cos(dz) * cos(dy) * ctx.face[i].vertex[1].x +
(cos(dz) * sin(dy) * sin(dx) - sin(dz) * cos(dx)) *
ctx.face[i].vertex[1].y +
(cos(dz) * sin(dy) * cos(dx) + sin(dz) * sin(dx)) *
ctx.face[i].vertex[1].z,
[1].y = sin(dz) * cos(dy) * ctx.face[i].vertex[1].x +
(sin(dz) * sin(dy) * sin(dx) + cos(dz) * cos(dx)) *
ctx.face[i].vertex[1].y +
(sin(dz) * sin(dy) * cos(dx) - cos(dz) * sin(dx)) *
ctx.face[i].vertex[1].z,
[1].z = -sin(dy) * ctx.face[i].vertex[1].x +
cos(dy) * sin(dx) * ctx.face[i].vertex[1].y +
cos(dy) * cos(dx) * ctx.face[i].vertex[1].z,
[2].x = cos(dz) * cos(dy) * ctx.face[i].vertex[2].x +
(cos(dz) * sin(dy) * sin(dx) - sin(dz) * cos(dx)) *
ctx.face[i].vertex[2].y +
(cos(dz) * sin(dy) * cos(dx) + sin(dz) * sin(dx)) *
ctx.face[i].vertex[2].z,
[2].y = sin(dz) * cos(dy) * ctx.face[i].vertex[2].x +
(sin(dz) * sin(dy) * sin(dx) + cos(dz) * cos(dx)) *
ctx.face[i].vertex[2].y +
(sin(dz) * sin(dy) * cos(dx) - cos(dz) * sin(dx)) *
ctx.face[i].vertex[2].z,
[2].z = -sin(dy) * ctx.face[i].vertex[2].x +
cos(dy) * sin(dx) * ctx.face[i].vertex[2].y +
cos(dy) * cos(dx) * ctx.face[i].vertex[2].z}};
}
return (struct object3D){.faces = ctx.faces, .face = face};
}
static struct vec3D cross_product(const struct vec3D a, const struct vec3D b) {
/* designated initializers */
return (struct vec3D){.x = a.y * b.z - a.z * b.y,
.y = a.z * b.x - a.x * b.z,
.z = a.x * b.y - a.y * b.x};
}
static struct vec3D normalize(const struct vec3D ctx) {
double mg = magnitude(ctx);
return (struct vec3D){.x = ctx.x / mg, .y = ctx.y / mg, .z = ctx.z / mg};
}
int main(int argc, char *argv[]) {
double Pz = 150.0;
(void)(width = 1000), height = 720;
struct triangle3D face[] = {
#include "faces.txt"
};
struct object3D box = {.faces = 8, .face = face};
struct vec3D light_source = {
.x = 0.0, .y = 0.0, .z = -1.0}; /* magnitude = 1 */
int frame_ctr = 0;
#pragma omp parallel for
for (int i = 0; i < FRAMES; i++) {
char buff[100] = {0};
sprintf(buff, "tt-%03d.png", i);
FILE *fp = fopen(buff, "wb");
assert(fp != NULL);
printf("\r%s: %d/%d", buff, frame_ctr++, FRAMES - 1);
fflush(stdout);
png_structp png =
png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
assert(png);
png_infop info = png_create_info_struct(png);
assert(info);
int tem = setjmp(png_jmpbuf(png));
assert(!tem);
png_init_io(png, fp);
png_set_IHDR(png, info, width, height, 8, PNG_COLOR_TYPE_RGBA,
PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
PNG_FILTER_TYPE_DEFAULT);
png_write_info(png, info);
png_bytep *row = NULL;
row = malloc(sizeof(png_bytep) * height);
assert(row != NULL);
for (int y = 0; y < height; y++) {
row[y] = malloc(sizeof(png_bytep) * width);
assert(row[y] != NULL);
}
for (int y = 0; y < height; y++) {
png_bytep line = row[y];
for (int x = 0; x < width; x++) {
double Px = x - (width / 2), Py = (height / 2) - y;
struct vec3D ray = {Px, Py, Pz};
double _magnitude = magnitude(ray);
struct vec3D normalized_ray = {ray.x / _magnitude, ray.y / _magnitude,
ray.z / _magnitude};
/* RANDOM SPEED */
struct object3D rotbox =
rotate(box, (double)i * 3.0 / 180.0, M_PI * (double)i * 4.0 / 180.0,
(double)i * 7.0 / 180.0);
struct object3D trbox = translate(rotbox, 0.0, 0.0, 100.0);
free(rotbox.face);
struct vec3D BmA;
struct vec3D CmA;
struct vec3D pvec;
double illumination;
double det, t = INFINITY; /* portable? */
int intersect = 0;
/* check if all triangle intersects */
for (int triangle = 0; triangle < trbox.faces; triangle++) {
BmA = (struct vec3D){.x = trbox.face[triangle].vertex[1].x -
trbox.face[triangle].vertex[0].x,
.y = trbox.face[triangle].vertex[1].y -
trbox.face[triangle].vertex[0].y,
.z = trbox.face[triangle].vertex[1].z -
trbox.face[triangle].vertex[0].z};
CmA = (struct vec3D){.x = trbox.face[triangle].vertex[2].x -
trbox.face[triangle].vertex[0].x,
.y = trbox.face[triangle].vertex[2].y -
trbox.face[triangle].vertex[0].y,
.z = trbox.face[triangle].vertex[2].z -
trbox.face[triangle].vertex[0].z};
pvec = (struct vec3D)cross_product(ray, CmA);
double illum =
dot_product(normalize(cross_product(BmA, CmA)), light_source);
det = dot_product(BmA, pvec);
double u = dot_product(pvec,
(struct vec3D){
.x = -trbox.face[triangle].vertex[0].x,
.y = -trbox.face[triangle].vertex[0].y,
.z = -trbox.face[triangle].vertex[0].z}) /
det;
if (u < 0.0 || u > 1.0) {
*(line + (x * 4) + 0) = 0xA0;
*(line + (x * 4) + 1) = 0xA0;
*(line + (x * 4) + 2) = 0xA0;
*(line + (x * 4) + 3) = 0xFF;
continue;
}
double v =
dot_product(
cross_product(
(struct vec3D){.x = -trbox.face[triangle].vertex[0].x,
.y = -trbox.face[triangle].vertex[0].y,
.z = -trbox.face[triangle].vertex[0].z},
BmA),
ray) /
det;
if (v < 0.0 || u + v > 1.0) {
*(line + (x * 4) + 0) = 0xA0;
*(line + (x * 4) + 1) = 0xA0;
*(line + (x * 4) + 2) = 0xA0;
*(line + (x * 4) + 3) = 0xFF;
continue;
}
double temp =
dot_product(CmA, cross_product(
(struct vec3D){
.x = -trbox.face[triangle].vertex[0].x,
.y = -trbox.face[triangle].vertex[0].y,
.z = -trbox.face[triangle].vertex[0].z},
BmA)) /
det; /*
double mm = magnitude((struct vec3D){normalized_ray.x*temp,
normalized_ray.y*temp, normalized_ray.z*temp});*/
if (t > temp) {
illumination = illum;
t = temp;
intersect = 1;
}
}
free(trbox.face);
if (!intersect) {
*(line + (x * 4) + 0) = 0xA0;
*(line + (x * 4) + 1) = 0xA0;
*(line + (x * 4) + 2) = 0xA0;
*(line + (x * 4) + 3) = 0xFF;
continue;
}
*(line + (x * 4) + 0) =
(unsigned char)(((illumination + 1.0) / 2.0) * 255.0);
*(line + (x * 4) + 1) =
(unsigned char)(((illumination + 1.0) / 2.0) * 255.0);
*(line + (x * 4) + 2) =
(unsigned char)(((illumination + 1.0) / 2.0) * 255.0);
*(line + (x * 4) + 3) = 0xFF;
}
}
png_write_image(png, row);
png_write_end(png, NULL);
for (int y = 0; y < height; y++)
free(row[y]);
free(row);
fclose(fp);
png_destroy_write_struct(&png, &info);
}
putchar('\n');
return 0;
}
Raw
faces.txt
[0].vertex = {[0].x = -20.0,
[0].y = -50.0,
[0].z = -20.0,
[1].x = -20.0,
[1].y = 50.0,
[1].z = -20.0,
[2].x = 20.0,
[2].y = 50.0,
[2].z = -20.0},
[1].vertex = {[0].x = -20.0,
[0].y = -50.0,
[0].z = -20.0,
[1].x = 20.0,
[1].y = 50.0,
[1].z = -20.0,
[2].x = 20.0,
[2].y = -50.0,
[2].z = -20.0},
[2].vertex = {[2].x = -20.0,
[2].y = -50.0,
[2].z = 20.0,
[1].x = -20.0,
[1].y = 50.0,
[1].z = 20.0,
[0].x = 20.0,
[0].y = 50.0,
[0].z = 20.0},
[3].vertex = {[2].x = -20.0,
[2].y = -50.0,
[2].z = 20.0,
[1].x = 20.0,
[1].y = 50.0,
[1].z = 20.0,
[0].x = 20.0,
[0].y = -50.0,
[0].z = 20.0},
[4].vertex = {[2].x = -20.0,
[2].y = -50.0,
[2].z = -20.0,
[1].x = -20.0,
[1].y = 50.0,
[1].z = -20.0,
[0].x = -20.0,
[0].y = -50.0,
[0].z = 20.0},
[5].vertex = {[0].x = -20.0,
[0].y = -50.0,
[0].z = 20.0,
[1].x = -20.0,
[1].y = 50.0,
[1].z = 20.0,
[2].x = -20.0,
[2].y = 50.0,
[2].z = -20.0},
[6].vertex = {[0].x = 20.0,
[0].y = -50.0,
[0].z = -20.0,
[1].x = 20.0,
[1].y = 50.0,
[1].z = -20.0,
[2].x = 20.0,
[2].y = -50.0,
[2].z = 20.0},
[7].vertex = {[2].x = 20.0,
[2].y = -50.0,
[2].z = 20.0,
[1].x = 20.0,
[1].y = 50.0,
[1].z = 20.0,
[0].x = 20.0,
[0].y = 50.0,
[0].z = -20.0}
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