// ------------------------- Grain --------------------------------------------

//uniform sampler2D bgl_RenderedTexture; //rendered scene sampler
//uniform float bgl_RenderedTextureWidth; //scene sampler width
//uniform float bgl_RenderedTextureHeight; //scene sampler height
//uniform float timer;

const float permTexUnit = 1.0/256.0;        // Perm texture texel-size
const float permTexUnitHalf = 0.5/256.0;    // Half perm texture texel-size

//float width = tex.x;
//float height = tex.y;

const float grainamount = 0.05; //grain amount
bool colored = false; //colored noise?
float coloramount = 0.6;
float grainsize = 1.6; //grain particle size (1.5 - 2.5)
float lumamount = 1.0; //

float fract (float inp)
{
    return (inp-floor(inp));
}

float4 mix (float x, float y, float a)
{
    return x * (1 - a) + y * a;
}

//a random texture generator, but you can also use a pre-computed perturbation texture
float4 rnm(in float2 tc)
{
    float noise =  sin(dot(tc + float2(timer,timer),float2(12.9898,78.233))) * 43758.5453;

    float noiseR =  fract(noise)*2.0-1.0;
    float noiseG =  fract(noise*1.2154)*2.0-1.0;
    float noiseB =  fract(noise*1.3453)*2.0-1.0;
    float noiseA =  fract(noise*1.3647)*2.0-1.0;

    return float4(noiseR,noiseG,noiseB,noiseA);
}

float fade(in float t) {
    return t*t*t*(t*(t*6.0-15.0)+10.0);
}

float pnoise3D(in float3 p)
{
    float3 pi = permTexUnit*floor(p)+permTexUnitHalf; // Integer part, scaled so +1 moves permTexUnit texel
    // and offset 1/2 texel to sample texel centers
    float3 pf = fract(p);     // Fractional part for interpolation

    // Noise contributions from (x=0, y=0), z=0 and z=1
    float perm00 = rnm(pi.xy).a ;
    float3  grad000 = rnm(float2(perm00, pi.z)).rgb * 4.0 - 1.0;
    float n000 = dot(grad000, pf);
    float3  grad001 = rnm(float2(perm00, pi.z + permTexUnit)).rgb * 4.0 - 1.0;
    float n001 = dot(grad001, pf - float3(0.0, 0.0, 1.0));

    // Noise contributions from (x=0, y=1), z=0 and z=1
    float perm01 = rnm(pi.xy + float2(0.0, permTexUnit)).a ;
    float3  grad010 = rnm(float2(perm01, pi.z)).rgb * 4.0 - 1.0;
    float n010 = dot(grad010, pf - float3(0.0, 1.0, 0.0));
    float3  grad011 = rnm(float2(perm01, pi.z + permTexUnit)).rgb * 4.0 - 1.0;
    float n011 = dot(grad011, pf - float3(0.0, 1.0, 1.0));

    // Noise contributions from (x=1, y=0), z=0 and z=1
    float perm10 = rnm(pi.xy + float2(permTexUnit, 0.0)).a ;
    float3  grad100 = rnm(float2(perm10, pi.z)).rgb * 4.0 - 1.0;
    float n100 = dot(grad100, pf - float3(1.0, 0.0, 0.0));
    float3  grad101 = rnm(float2(perm10, pi.z + permTexUnit)).rgb * 4.0 - 1.0;
    float n101 = dot(grad101, pf - float3(1.0, 0.0, 1.0));

    // Noise contributions from (x=1, y=1), z=0 and z=1
    float perm11 = rnm(pi.xy + float2(permTexUnit, permTexUnit)).a ;
    float3  grad110 = rnm(float2(perm11, pi.z)).rgb * 4.0 - 1.0;
    float n110 = dot(grad110, pf - float3(1.0, 1.0, 0.0));
    float3  grad111 = rnm(float2(perm11, pi.z + permTexUnit)).rgb * 4.0 - 1.0;
    float n111 = dot(grad111, pf - float3(1.0, 1.0, 1.0));

    // Blend contributions along x
    float4 n_x = mix(float4(n000, n001, n010, n011), float4(n100, n101, n110, n111), fade(pf.x));

    // Blend contributions along y
    float2 n_xy = mix(n_x.xy, n_x.zw, fade(pf.y));

    // Blend contributions along z
    float n_xyz = mix(n_xy.x, n_xy.y, fade(pf.z));

    // We're done, return the final noise value.
    return n_xyz;
}

//2d coordinate orientation thing
float2 coordRot(in float2 tc, in float angle, in float width, in float height)
{
    float aspectr = width/height;
    float rotX = ((tc.x*2.0-1.0)*aspectr*cos(angle)) - ((tc.y*2.0-1.0)*sin(angle));
    float rotY = ((tc.y*2.0-1.0)*cos(angle)) + ((tc.x*2.0-1.0)*aspectr*sin(angle));
    rotX = ((rotX/aspectr)*0.5+0.5);
    rotY = rotY*0.5+0.5;
    return float2(rotX,rotY);
}

float4 GrainPass( float4 colorInput, float2 tex )
{
    float width = tex.x;
    float height = tex.y;
    //float aspectr = (width / height);
    float2 texCoord = float2 (tex[0], tex[1]);

    float3 rotOffset = float3(1.425,3.892,5.835); //rotation offset values
    float2 rotCoordsR = coordRot(texCoord, timer + rotOffset.x, width, height);
    //float3 noise = float3(pnoise3D(float3(rotCoordsR*float2(width/grainsize,height/grainsize),0.0)));
    float2 rot = rotCoordsR*float2(width/grainsize,height/grainsize);
    float pNoise = pnoise3D(float3(rot.x,rot.y,0.0));
    float3 noise = float3(pNoise, pNoise, pNoise);

    if (colored)
    {
        float2 rotCoordsG = coordRot(texCoord, timer + rotOffset.y, width, height);
        float2 rotCoordsB = coordRot(texCoord, timer + rotOffset.z, width, height);
        noise.g = mix(noise.r,pnoise3D(float3(rotCoordsG*float2(width/grainsize,height/grainsize),1.0)),coloramount);
        noise.b = mix(noise.r,pnoise3D(float3(rotCoordsB*float2(width/grainsize,height/grainsize),2.0)),coloramount);
    }

    float3 col = colorInput.rgb;

    //noisiness response curve based on scene luminance
    float3 lumcoeff = float3(0.299,0.587,0.114);
    float luminance = mix(0.0,dot(col, lumcoeff),lumamount);
    float lum = smoothstep(0.2,0.0,luminance);
    lum += luminance;


    noise = mix(noise,0.0,pow(lum,4.0));
    col = col+noise*grainamount;

    return float4(col,1.0);
}