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#include <limits.h>
#include <float.h>
#include <stdint.h>
#include <math.h>
#include "vecmath.h"
#include "picture.h"
#define EPSILON 0.001
typedef enum {
kAmbientLight,
kPointLight,
kDirectionalLight,
} LightType;
typedef struct {
LightType type;
float intensity;
Vec3f vec;
} Light;
Vec3f screen_proj(int width, int height, Vec2i sp) {
Vec3f ret;
float maxlen = width > height ? width : height;
ret.z = 1.0;
ret.x = (sp.x - width / 2.0) / maxlen;
ret.y = (-sp.y + height / 2.0) / maxlen;
return ret;
}
typedef struct {
Vec3f center;
float r;
Color color;
float specular;
} Ball;
Ball balls[] = {
{
.center = {.x = 0, .y = -1, .z = 3},
.r = 1,
.specular = 500,
},
{
.center = {.x = 2, .y = 0, .z = 4},
.r = 1,
.specular = 500,
},
{
.center = {.x = -2, .y = 0, .z = 4},
.r = 1,
.specular = 10,
},
{
.center = {0, -5001, 0},
.r = 5000,
.specular = 1000,
},
};
Light lights[] = {
{
.type = kAmbientLight,
.intensity = 0.2,
},
{
.type = kPointLight,
.intensity = 0.6,
.vec = {2.0, 1.0, 0.0},
},
{
.type = kDirectionalLight,
.intensity = 0.2,
.vec = {1.0, 4.0, 4.0}
},
};
Color gBackgroupColor = {0,0,0};
void init_color() {
balls[0].color = icolor(0x95e1d3);
balls[1].color = icolor(0xfce38a);
balls[2].color = icolor(0xf38181);
balls[3].color = icolor(0xeaffd0);
gBackgroupColor = icolor(0xeaeaea);
}
float ball_intersect(Vec3f start, Vec3f ray, Ball *ball) {
Vec3f sc = vec3f_sub(start, ball->center);
float a = vec3f_dot(ray, ray);
float b = 2 * vec3f_dot(sc, ray);
float c = vec3f_dot(sc, sc) - ball->r * ball->r;
float delta = b*b - 4*a*c;
if (delta < 0) {
return -1;
}
float t1 = (-b + sqrt(delta)) / (2*a);
float t2 = (-b - sqrt(delta)) / (2*a);
return t1 < t2 ? t1 : t2;
}
bool is_in_shadow(Vec3f pos, Light light) {
Vec3f ray;
if (light.type == kPointLight) {
ray = vec3f_sub(light.vec, pos);
} else if (light.type == kDirectionalLight) {
ray = light.vec;
} else {
return false;
}
float tmin = FLT_MAX;
for (int i = 0; i < sizeof(balls) / sizeof(Ball); i++) {
float t = ball_intersect(pos, ray, &balls[i]);
if (t > EPSILON && t < tmin) tmin = t;
}
if (light.type == kPointLight) {
return tmin < 1;
}
if (light.type == kDirectionalLight) {
return tmin != FLT_MAX;
}
return false;
}
float specular_coeff(Vec3f l, Vec3f n, Vec3f v, float s) {
Vec3f r = vec3f_sub(vec3f_mul(2 * vec3f_dot(n, l), n), l);
v = vec3f_normalize(v);
float prod = vec3f_dot(r, vec3f_neg(v));
if (prod < 0) return 0;
else return pow(vec3f_dot(r, vec3f_neg(v)), s);
}
Color ball_surface_color(Ball *ball, Vec3f point, Vec3f view) {
Vec3f norm = vec3f_normalize(vec3f_sub(point, ball->center));
float amp = 0;
for (int i = 0; i < sizeof(lights) / sizeof(Light); i++) {
if (lights[i].type == kAmbientLight) {
amp += lights[i].intensity;
} else if (lights[i].type == kPointLight) {
if (is_in_shadow(point, lights[i])) continue;
Vec3f l = vec3f_normalize(vec3f_sub(lights[i].vec, point));
float prod = vec3f_dot(l, norm);
if (prod > 0) amp += prod * lights[i].intensity;
if (ball->specular > 0) {
amp += specular_coeff(l, norm, view, ball->specular)
* lights[i].intensity;
}
} else if (lights[i].type == kDirectionalLight) {
if (is_in_shadow(point, lights[i])) continue;
Vec3f l = vec3f_normalize(lights[i].vec);
float prod = vec3f_dot(l, norm);
if (prod > 0) amp += prod * lights[i].intensity;
if (ball->specular > 0) {
amp += specular_coeff(l, norm, view, ball->specular)
* lights[i].intensity;
}
}
}
return (Color){
ball->color.r * amp,
ball->color.g * amp,
ball->color.b * amp
};
}
Color calc_color(Vec3f v) {
Vec3f start = {.x = 0, .y = 0, .z = 0};
float tmin = 0.1;
float tmax = FLT_MAX;
int nearest_idx = -1;
float t_nearest = FLT_MAX;
for (int i = 0; i < sizeof(balls) / sizeof(Ball); i++) {
float t = ball_intersect(start, v, &balls[i]);
if (t < t_nearest && t < tmax && t > tmin) {
t_nearest = t;
nearest_idx = i;
}
}
if (nearest_idx >= 0) {
Vec3f intersection = vec3f_add(start, vec3f_mul(t_nearest, v));
return ball_surface_color(&balls[nearest_idx], intersection, v);
} else {
return gBackgroupColor;
}
}
int main() {
init_color();
int img_w = 800*2;
int img_h = 800*2;
Picture pic = new_picture(img_w, img_h);
for (int x = 0; x < img_w; x++) {
for (int y = 0; y < img_h; y++) {
Vec2i screen_pos = {x, y};
Vec3f v = screen_proj(img_w, img_h, screen_pos);
set_pixel(pic, screen_pos, calc_color(v));
}
}
Picture newpic = picture_downscale_2x(pic);
writeBMP("test.bmp", newpic);
delete_picture(pic);
delete_picture(newpic);
return 0;
}
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