#include<stdio.h>
#include<math.h>

const int max_iterations = 128;
const float stop_threshold = 0.01f;
const float grad_step = 0.01f;
const float clip_far = 10.0f;

const float PI = 3.14159265359f;
const float PI2 = 6.28318530718f;
const float DEG_TO_RAD = PI / 180.0f;

typedef struct { float x, y; }vec2;
typedef struct { float x, y,z; }vec3;
typedef struct { float m[9]; }mat3;

const vec3 light_pos = { 20.0f,50.0f,20.0f };

float min(float a, float b){return a < b ? a : b;}
float max(float a, float b){return a > b ? a : b;}
float clamp(float f, float a, float b) { return max(min(f, b), a); }
vec2 make2(float x, float y) { vec2 r = { x,y }; return r; }
vec2 add2(vec2 a, vec2 b) { vec2 r = { a.x + b.x,a.y + b.y }; return r; }
vec2 sub2(vec2 a, vec2 b) { vec2 r = { a.x - b.x,a.y - b.y }; return r; }
float dot2(vec2 a, vec2 b) { return a.x * b.x + a.y * b.y; }
float length2(vec2 v) { return sqrt(dot2(v, v)); }
vec3 make3(float x, float y, float z) { vec3 r = { x,y,z }; return r; }
vec3 add3(vec3 a, vec3 b) { vec3 r = { a.x + b.x,a.y + b.y,a.z + b.z }; return r; }
vec3 sub3(vec3 a, vec3 b) { vec3 r = { a.x - b.x,a.y - b.y,a.z - b.z }; return r; }
vec3 mul3(vec3 a, vec3 b) { vec3 r = { a.x * b.x,a.y * b.y,a.z * b.z }; return r; }
vec3 scale3(vec3 v, float s) { vec3 r = { v.x * s,v.y * s,v.z * s }; return r; }
float dot3(vec3 a, vec3 b) { return a.x * b.x + a.y * b.y + a.z * b.z; }
float length3(vec3 v) { return sqrt(dot3(v, v)); }
vec3 normalize3(vec3 v) { return scale3(v, 1.0f / length3(v)); }
vec3 mul(mat3 m, vec3 v) {
	return make3(
		m.m[0] * v.x + m.m[3] * v.y + m.m[6] * v.z,
		m.m[1] * v.x + m.m[4] * v.y + m.m[7] * v.z,
		m.m[2] * v.x + m.m[5] * v.y + m.m[8] * v.z );
}

mat3 rotationXY(float x, float y) {
	vec2 c = { cos(x),cos(y) }, s = { sin(x),sin(y) };
	mat3 m = {
		c.y   ,0.0f,-s.y,
		s.y * s.x,c.x,c.y * s.x,
		s.y * c.x,-s.x,c.y * c.x
	};
	return m;
}

float opI(float d1, float d2) { return max(d1, d2); }
float opU(float d1, float d2) { return min(d1, d2); }
float opS(float d1, float d2) { return max(-d1, d2); }

float sdPetal(vec3 p, float s) {
	p = add3(mul3(p, make3(0.8f, 1.5f, 0.8f)), make3(0.1f, 0.0f, 0.0f));
	vec2 q = make2(length2(make2(p.x, p.z)), p.y);

	float lower = length2(q) - 1.0f;
	lower = opS(length2(q) - 0.97f, lower);
	lower = opI(lower, q.y);

	float upper = length2(sub2(q, make2(s, 0.0f))) + 1.0f - s;
	upper = opS(upper, length2(sub2(q, make2(s, 0.0f))) + 0.97f - s);
	upper = opI(upper, -q.y);
	upper = opI(upper, q.x - 2.0f);

	float region = length3(sub3(p, make3(1.0f, 0.0f, 0.0f))) - 1.0f;
	return opI(opU(upper, lower), region);
}

float map(vec3 p) {
	float d = 1000.0f, s = 2.0f;
	mat3 r = rotationXY(0.1f, PI2 * 0.618034f);
	r.m[0] *= 1.08f; r.m[1] *= 1.08f; r.m[2] *= 1.08f;
	r.m[3] *= 0.995f; r.m[4] *= 0.995f; r.m[5] *= 0.995f;
	r.m[6] *= 1.08f; r.m[7] *= 1.08f; r.m[8] *= 1.08f;
	for (int i = 0; i < 21; i++) {
		d = opU(d, sdPetal(p, s));
		p = mul(r, p);
		p = add3(p, make3(0.0, -0.02, 0.0));
		s *= 1.05f;
	}
	return d;
}

vec3 gradient(vec3 pos) {
	const vec3 dx = { grad_step,0.0,0.0 };
	const vec3 dy = { 0.0,grad_step,0.0 };
	const vec3 dz = { 0.0,0.0,grad_step };
	return normalize3(make3(
		map(add3(pos, dx)) - map(sub3(pos, dx)),
		map(add3(pos, dy)) - map(sub3(pos, dy)),
		map(add3(pos, dz)) - map(sub3(pos, dz))));
}

float ray_marching(vec3 origin, vec3 dir, float start, float end) {
	float depth = start;
	for (int i = 0; i < max_iterations; i++) {
		float dist = map(add3(origin, scale3(dir, depth)));
		if (dist < stop_threshold)
			return depth;
		depth += dist * 0.3;
		if (depth >= end)
			return end;
	}
	return end;
}

float shading(vec3 v, vec3 n, vec3 eye) {
	vec3 ev = normalize3(sub3(v, eye));
	vec3 vl = normalize3(sub3(light_pos, v));
	float diffuse = dot3(vl, n) * 0.5f + 0.5f;
	vec3 h = normalize3(sub3(vl, ev));
	float rim = pow(1.0f - max(-dot3(n, ev), 0.0f), 2.0f) * 0.15f;
	float ao = clamp(v.y * 0.5f + 0.5f, 0.0f, 1.0f);
	return(diffuse + rim) * ao;
}

vec3 ray_dir(float fov, vec2 pos) {
	vec3 r = { pos.x,pos.y,-tan((90.0f - fov * 0.5f) * DEG_TO_RAD) };
	return normalize3(r);
}
	
float f(vec2 fragCoord) {
	vec3 dir = ray_dir(45.0f, fragCoord);
	vec3 eye = { 0.0f,0.0f,4.5f };
	mat3 rot = rotationXY(-1.0f, 1.0f);

	dir = mul(rot, dir);
	eye = mul(rot, eye);

	float depth = ray_marching(eye, dir, 0.0f, clip_far);
	vec3 pos = add3(eye, scale3(dir, depth));
	if (depth >= clip_far)
		return 0.0f;
	else
		return shading(pos, gradient(pos), eye);
}

int main() {
	puts("\033[91m");
		for (int y=0;y<80;y++){
			for (int x = 0; x < 160; x++)
				putchar(".,-:;+=*#@"[(int)(f(make2((x / 160.0f - 0.5f )*2.0f,(y/80.0f-0.5f)*-2.0f))*12.0f)]);
			putchar('\n');
		}
}