// --------------------------------
// common lighting operations
// --------------------------------

float3 lRenderSun(float3 ray_dir, float3 sun_dir, float3 sun_col = float3(0.8, 0.4, 0.1)) {
	float alignment = min(acos(dot(ray_dir, sun_dir)), 1);
	float sun_amount = pow(0.025/alignment, 3);
	return sun_amount * sun_col;
}

// a basic procedural sky
float3 lRenderSky(float3 ray_dir, float3 sun_dir) {
	float3 rendered_sun = lRenderSun(ray_dir, sun_dir);
	float a = 1 - abs(ray_dir.y);
	return lerp(float3(0.3, 0.3, 0.7), float3(0.6, 0.7, 0.9), a) + rendered_sun;
}

//calculate sky light
float3 lSky(float3 normal, float3 sky_col = float3(0.35, 0.43, 0.46)) {
	return sky_col * (0.5 + 0.5 * normal.y);
}

float lSun(float3 normal, float3 sun_dir, float3 sun_col = float3(1, 0.78, 0.43)) {
	return sun_col * max(dot(normal, sun_dir), 0);
}

// soft shadows
float lShadow(float3 p, float3 sun_dir, float sharpness = 8) {
	float shadow = 1;
	for (float ray_len = 0.001; ray_len < MAX_DIST / 2.0;)
	{
		float dist = DISTANCE_FN(p + sun_dir * ray_len);
		if (dist < SURF_DIST) return 0;
		shadow = min(shadow, sharpness * dist / ray_len);
		ray_len += dist;
	}
	return shadow;
}

// max ray steps, from last bounce (reset on each reflection)
#ifndef SHADOW_MAX_STEPS
#define SHADOW_MAX_STEPS 128
#endif

// max ray length, from last bounce (length is reset on each reflection)
#ifndef SHADOW_MAX_DIST
#define SHADOW_MAX_DIST 128
#endif

// the largest surface distance that is counted as a hit
#ifndef SHADOW_SURF_DIST
#define SHADOW_SURF_DIST 0.001
#endif

// soft shadows
// float lShadow(float3 p, float3 sun_dir, float sharpness = 8) {
// 	float light = 1;
// 	float ray_len = SHADOW_SURF_DIST*2;
// 	for (int steps = 0; steps < SHADOW_MAX_STEPS; steps++) {
// 		float dist = DISTANCE_FN(p + sun_dir * ray_len);
// 		light = min(light, sharpness * dist / ray_len);
// 		ray_len += dist;
// 		if (dist < SHADOW_SURF_DIST) return 0;
// 		if (ray_len > SHADOW_MAX_DIST) return light;
// 	}
// 	return light;
// }

// --------------------------------
// misc
// --------------------------------

float3 HSV(float h, float s, float v) {
	h *= 6;
	float c = s * v;
	float x = c * (1 - abs(fmod(h, 2) - 1));
	float m = v - c;
	c += m;
	x += m;

	float3 colors[6] = {
		float3(c, x, m),
		float3(x, c, m),
		float3(m, c, x),
		float3(m, x, c),
		float3(x, m, c),
		float3(c, m, x)};

	return colors[int(h)];
}