functions.cginc

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float3 RGBtoHSV(float3 c)
{
    float4 K = float4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
    float4 p = lerp(float4(c.bg, K.wz), float4(c.gb, K.xy), step(c.b, c.g));
    float4 q = lerp(float4(p.xyw, c.r), float4(c.r, p.yzx), step(p.x, c.r));

    float d = q.x - min(q.w, q.y);
    float e = 1.0e-10;
    return float3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);
}

float3 HSVtoRGB(float3 c)
{
    float4 K = float4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
    float3 p = abs(frac(c.xxx + K.xyz) * 6.0 - K.www);
    return float3(c.z * lerp(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y));
}

float3 oppositeColor(float3 color1, float3 color2)
{
    float3 color1hsv = RGBtoHSV(color1);
    float3 color2hsv = RGBtoHSV(color2);
    float3 oppositeColor = float3(fmod(((color1hsv.x * 360) + 180), 360) / 360, color2hsv.yz);

    return HSVtoRGB(oppositeColor);
}

bool equalHue(float3 color1, float3 color2)
{
    float3 color1hsv = RGBtoHSV(color1);
    float3 color2hsv = RGBtoHSV(color2);

    if (abs(color1hsv.x - color2hsv.x) < 0.05)
        return true;
    else
        return false;
}

float3 huePreservingColorAdd(float3 color1, float3 color2)
{
    if (equalHue(color1, color2))
        return color1 + color2;

    float3 color2Prime = oppositeColor(color1, color2);
    float3 result = color1 + color2Prime;

    // If color1 was the dominant color, the result should now be the same hue as color1.
    // If this isn't the case, switch colors.
    if (!equalHue(color1, result))
    {
        float3 color1Prime = oppositeColor(color2, color1);
        result = color1Prime + color2;
    }

    return result;
}

/*
float3 huePreservingColorAddBias(float3 color1, float3 color2, float bias)
{
    if (equalHue(color1, color2))
        return color1 + color2;

    float3 color2Prime = oppositeColor(color1, color2);
    float3 result = color1 + color2Prime;

    if (!equalHue(color1, result))
    {
        float3 color1Prime = oppositeColor(color2, color1);
        result = lerp(color1Prime + color2, color2, bias);
    } else {
        result = lerp(color1 + color2Prime, color1, bias);
    }

    return result;
}
*/

/*
float4 blendFrontToBack(float4 src, float4 dest)
{
    // Front to back blending:
    // GL_ONE_MINUS_DST_ALPHA, GL_ONE

    //finalColor.rgb = finalColor.rgb + (1.0 - finalColor.a) * color.rgb;
    //finalColor.a = finalColor.a + (1.0 - finalColor.a) * color.a;

    src.rgb *= src.a;
    dest = (1.0 - dest.a) * src + dest;

    return dest;
}

float4 blendBackToFront(float4 src, float4 dest)
{
    src.rgb *= src.a;
    dest = src + (1.0 - src.a) * dest;

    //dest = src.a * src + (1.0 - src.a) * dest;

    return dest;
}
*/