#define TIME_MULT 1.0
#define TIME (frameTimeCounter * TIME_MULT)

const float PI1 = 3.14159265;
const float TAU = PI1 * 2.0;
const float hPI = PI1 * 0.5;
const float rPI = 1.0 / PI1;
const float rTAU = 1.0 / TAU;

const float PHI = sqrt(5.0) * 0.5 + 0.5;
const float rLOG2 = 1.0 / log(2.0);

const float goldenAngle = TAU / PHI / PHI;

#define clamp01(x) clamp(x, 0.0, 1.0)
#define max0(x) max(x, 0.0)
#define min0(x) min(x, 0.0)
#define max3(a) max(max(a.x, a.y), a.z)
#define min3(a) min(min(a.x, a.y), a.z)
#define max4(a, b, c, d) max(max(a, b), max(c, d))
#define min4(a, b, c, d) min(min(a, b), min(c, d))

#define fsign(x) (clamp01(x * 1e35) * 2.0 - 1.0)
#define fstep(x, y) clamp01((y - x) * 1e35)

#define diagonal2(m) vec2((m)[0].x, (m)[1].y)
#define diagonal3(m) vec3(diagonal2(m), m[2].z)
#define diagonal4(m) vec4(diagonal3(m), m[2].w)

#define transMAD(mat, v) (mat3(mat) * (v) + (mat)[3].xyz)
#define projMAD(mat, v) (diagonal3(mat) * (v) + (mat)[3].xyz)

#define encodeColor(x) (x * 0.00005)
#define decodeColor(x) (x * 20000.0)

#define cubeSmooth(x) (x * x * (3.0 - 2.0 * x))

#define lumCoeff vec3(0.2125, 0.7154, 0.0721)

float facos(const float sx)
{
    float x = clamp(abs(sx), 0., 1.);
    float a = sqrt(1. - x) * (-0.16882 * x + 1.56734);
    return sx > 0. ? a : PI - a;
    // float c = clamp(-sx * 1e35, 0., 1.);
    // return c * pi + a * -(c * 2. - 1.); //no conditional version
}

vec2 sincos(float x)
{
    return vec2(sin(x), cos(x));
}

vec2 circlemap(float i, float n)
{
    return sincos(i * n * goldenAngle) * sqrt(i);
}

vec3 circlemapL(float i, float n)
{
    return vec3(sincos(i * n * goldenAngle), sqrt(i));
}

vec3 calculateRoughSpecular(const float i, const float alpha2, const int steps)
{

    float x = (alpha2 * i) / (1.0 - i);
    float y = i * float(steps) * 64.0 * 64.0 * goldenAngle;

    float c = inversesqrt(x + 1.0);
    float s = sqrt(x) * c;

    return vec3(cos(y) * s, sin(y) * s, c);
}

vec3 clampNormal(vec3 n, vec3 v)
{
    float NoV = clamp(dot(n, -v), 0., 1.);
    return normalize(NoV * v + n);
}

vec3 srgbToLinear(vec3 srgb)
{
    return mix(
        srgb / 12.92,
        pow(.947867 * srgb + .0521327, vec3(2.4)),
        step(.04045, srgb));
}

vec3 linearToSRGB(vec3 linear)
{
    return mix(
        linear * 12.92,
        pow(linear, vec3(1. / 2.4)) * 1.055 - .055,
        step(.0031308, linear));
}

vec3 blackbody(float Temp)
{
    float t = pow(Temp, -1.5);
    float lt = log(Temp);

    vec3 col = vec3(0.0);
    col.x = 220000.0 * t + 0.58039215686;
    col.y = 0.39231372549 * lt - 2.44549019608;
    col.y = Temp > 6500. ? 138039.215686 * t + 0.72156862745 : col.y;
    col.z = 0.76078431372 * lt - 5.68078431373;
    col = clamp01(col);
    col = Temp < 1000. ? col * Temp * 0.001 : col;

    return srgbToLinear(col);
}

float calculateHardShadows(float shadowDepth, vec3 shadowPosition, float bias)
{
    if (shadowPosition.z >= 1.0)
        return 1.0;

    return 1.0 - fstep(shadowDepth, shadowPosition.z - bias);
}

vec3 genUnitVector(vec2 xy)
{
    xy.x *= TAU;
    xy.y = xy.y * 2.0 - 1.0;
    return vec3(sincos(xy.x) * sqrt(1.0 - xy.y * xy.y), xy.y);
}

vec2 rotate(vec2 x, float r)
{
    vec2 sc = sincos(r);
    return mat2(sc.x, -sc.y, sc.y, sc.x) * x;
}

vec3 cartToSphere(vec2 coord)
{
    coord *= vec2(TAU, PI);
    vec2 lon = sincos(coord.x) * sin(coord.y);
    return vec3(lon.x, 2.0 / PI * coord.y - 1.0, lon.y);
}

vec2 sphereToCart(vec3 dir)
{
    float lonlat = atan(-dir.x, -dir.z);
    return vec2(lonlat * rTAU + 0.5, 0.5 * dir.y + 0.5);
}

mat3 getRotMat(vec3 x, vec3 y)
{
    float d = dot(x, y);
    vec3 cr = cross(y, x);

    float s = length(cr);

    float id = 1. - d;

    vec3 m = cr / s;

    vec3 m2 = m * m * id + d;
    vec3 sm = s * m;

    vec3 w = (m.xy * id).xxy * m.yzz;

    return mat3(
        m2.x, w.x - sm.z, w.y + sm.y,
        w.x + sm.z, m2.y, w.z - sm.x,
        w.y - sm.y, w.z + sm.x, m2.z);
}

// No intersection if returned y component is < 0.0
vec2 rsi(vec3 position, vec3 direction, float radius)
{
    float PoD = dot(position, direction);
    float radiusSquared = radius * radius;

    float delta = PoD * PoD + radiusSquared - dot(position, position);
    if (delta < 0.0)
        return vec2(-1.0);
    delta = sqrt(delta);

    return -PoD + vec2(-delta, delta);
}
float HaltonSeq3(int index)
{
    float r = 0.;
    float f = 1.;
    int i = index;
    while (i > 0)
    {
        f /= 3.0;
        r += f * (i % 3);
        i = int(i / 3.0);
    }
    return r;
}
float HaltonSeq2(int index)
{
    float r = 0.;
    float f = 1.;
    int i = index;
    while (i > 0)
    {
        f /= 2.0;
        r += f * (i % 2);
        i = int(i / 2.0);
    }
    return r;
}
