fxaa.glsl

//!DESC FXAA Anti-aliasing
//!HOOK SCALED
//!BIND HOOKED

// FXAA implementation based on NVIDIA's FXAA 3.11 implementation

// FXAA preset configuration
#define FXAA_PRESET 5

#if (FXAA_PRESET == 3)
    #define FXAA_EDGE_THRESHOLD      (1.0/8.0)
    #define FXAA_EDGE_THRESHOLD_MIN  (1.0/24.0)
    #define FXAA_SEARCH_STEPS        16
    #define FXAA_SEARCH_THRESHOLD    (1.0/4.0)
    #define FXAA_SUBPIX_CAP          (3.0/4.0)
    #define FXAA_SUBPIX_TRIM         (1.0/4.0)
#endif
#if (FXAA_PRESET == 4)
    #define FXAA_EDGE_THRESHOLD      (1.0/8.0)
    #define FXAA_EDGE_THRESHOLD_MIN  (1.0/24.0)
    #define FXAA_SEARCH_STEPS        24
    #define FXAA_SEARCH_THRESHOLD    (1.0/4.0)
    #define FXAA_SUBPIX_CAP          (3.0/4.0)
    #define FXAA_SUBPIX_TRIM         (1.0/4.0)
#endif
#if (FXAA_PRESET == 5)
    #define FXAA_EDGE_THRESHOLD      (1.0/16.0)
    #define FXAA_EDGE_THRESHOLD_MIN  (1.0/16.0)
    #define FXAA_SEARCH_STEPS        32
    #define FXAA_SEARCH_THRESHOLD    (1.0/4.0)
    #define FXAA_SUBPIX_CAP          (7.0/8.0)
    #define FXAA_SUBPIX_TRIM         (1.0/4.0)
#endif

#define FXAA_SUBPIX_TRIM_SCALE (1.0/(1.0 - FXAA_SUBPIX_TRIM))

// Return the luma, the estimation of luminance from rgb inputs.
// This approximates luma using one FMA instruction,
// skipping normalization and tossing out blue.
// FxaaLuma() will range 0.0 to 2.963210702.
float FxaaLuma(vec3 rgb) {
    return rgb.y * (0.587/0.299) + rgb.x;
}

vec3 FxaaLerp3(vec3 a, vec3 b, float amountOfA) {
    return (vec3(-amountOfA) * b) + ((a * vec3(amountOfA)) + b);
}

vec4 FxaaTexOff(sampler2D tex, vec2 pos, ivec2 off, vec2 rcpFrame) {
    float x = pos.x + float(off.x) * rcpFrame.x;
    float y = pos.y + float(off.y) * rcpFrame.y;
    return texture(tex, vec2(x, y));
}

// pos is the output of FxaaVertexShader interpolated across screen.
// xy -> actual texture position {0.0 to 1.0}
// rcpFrame should be a uniform equal to {1.0/frameWidth, 1.0/frameHeight}
vec3 FxaaPixelShader(vec2 pos, sampler2D tex, vec2 rcpFrame) {
    vec3 rgbN = FxaaTexOff(tex, pos.xy, ivec2( 0,-1), rcpFrame).xyz;
    vec3 rgbW = FxaaTexOff(tex, pos.xy, ivec2(-1, 0), rcpFrame).xyz;
    vec3 rgbM = FxaaTexOff(tex, pos.xy, ivec2( 0, 0), rcpFrame).xyz;
    vec3 rgbE = FxaaTexOff(tex, pos.xy, ivec2( 1, 0), rcpFrame).xyz;
    vec3 rgbS = FxaaTexOff(tex, pos.xy, ivec2( 0, 1), rcpFrame).xyz;
    
    float lumaN = FxaaLuma(rgbN);
    float lumaW = FxaaLuma(rgbW);
    float lumaM = FxaaLuma(rgbM);
    float lumaE = FxaaLuma(rgbE);
    float lumaS = FxaaLuma(rgbS);
    float rangeMin = min(lumaM, min(min(lumaN, lumaW), min(lumaS, lumaE)));
    float rangeMax = max(lumaM, max(max(lumaN, lumaW), max(lumaS, lumaE)));
    
    float range = rangeMax - rangeMin;
    if(range < max(FXAA_EDGE_THRESHOLD_MIN, rangeMax * FXAA_EDGE_THRESHOLD)) {
        return rgbM;
    }
    
    vec3 rgbL = rgbN + rgbW + rgbM + rgbE + rgbS;
    
    float lumaL = (lumaN + lumaW + lumaE + lumaS) * 0.25;
    float rangeL = abs(lumaL - lumaM);
    float blendL = max(0.0, (rangeL / range) - FXAA_SUBPIX_TRIM) * FXAA_SUBPIX_TRIM_SCALE; 
    blendL = min(FXAA_SUBPIX_CAP, blendL);
    
    vec3 rgbNW = FxaaTexOff(tex, pos.xy, ivec2(-1,-1), rcpFrame).xyz;
    vec3 rgbNE = FxaaTexOff(tex, pos.xy, ivec2( 1,-1), rcpFrame).xyz;
    vec3 rgbSW = FxaaTexOff(tex, pos.xy, ivec2(-1, 1), rcpFrame).xyz;
    vec3 rgbSE = FxaaTexOff(tex, pos.xy, ivec2( 1, 1), rcpFrame).xyz;
    rgbL += (rgbNW + rgbNE + rgbSW + rgbSE);
    rgbL *= vec3(1.0/9.0);
    
    float lumaNW = FxaaLuma(rgbNW);
    float lumaNE = FxaaLuma(rgbNE);
    float lumaSW = FxaaLuma(rgbSW);
    float lumaSE = FxaaLuma(rgbSE);
    
    float edgeVert = 
        abs((0.25 * lumaNW) + (-0.5 * lumaN) + (0.25 * lumaNE)) +
        abs((0.50 * lumaW ) + (-1.0 * lumaM) + (0.50 * lumaE )) +
        abs((0.25 * lumaSW) + (-0.5 * lumaS) + (0.25 * lumaSE));
    float edgeHorz = 
        abs((0.25 * lumaNW) + (-0.5 * lumaW) + (0.25 * lumaSW)) +
        abs((0.50 * lumaN ) + (-1.0 * lumaM) + (0.50 * lumaS )) +
        abs((0.25 * lumaNE) + (-0.5 * lumaE) + (0.25 * lumaSE));
        
    bool horzSpan = edgeHorz >= edgeVert;
    float lengthSign = horzSpan ? -rcpFrame.y : -rcpFrame.x;
    
    if(!horzSpan) {
        lumaN = lumaW;
        lumaS = lumaE;
    }
    
    float gradientN = abs(lumaN - lumaM);
    float gradientS = abs(lumaS - lumaM);
    lumaN = (lumaN + lumaM) * 0.5;
    lumaS = (lumaS + lumaM) * 0.5;
    
    if (gradientN < gradientS) {
        lumaN = lumaS;
        lumaN = lumaS;
        gradientN = gradientS;
        lengthSign *= -1.0;
    }
    
    vec2 posN;
    posN.x = pos.x + (horzSpan ? 0.0 : lengthSign * 0.5);
    posN.y = pos.y + (horzSpan ? lengthSign * 0.5 : 0.0);
    
    gradientN *= FXAA_SEARCH_THRESHOLD;
    
    vec2 posP = posN;
    vec2 offNP = horzSpan ? vec2(rcpFrame.x, 0.0) : vec2(0.0, rcpFrame.y); 
    float lumaEndN = lumaN;
    float lumaEndP = lumaN;
    bool doneN = false;
    bool doneP = false;
    posN += offNP * vec2(-1.0, -1.0);
    posP += offNP * vec2( 1.0,  1.0);
    
    for(int i = 0; i < FXAA_SEARCH_STEPS; i++) {
        if(!doneN) {
            lumaEndN = FxaaLuma(texture(tex, posN.xy).xyz);
        }
        if(!doneP) {
            lumaEndP = FxaaLuma(texture(tex, posP.xy).xyz);
        }
        
        doneN = doneN || (abs(lumaEndN - lumaN) >= gradientN);
        doneP = doneP || (abs(lumaEndP - lumaN) >= gradientN);
        
        if(doneN && doneP) {
            break;
        }
        if(!doneN) {
            posN -= offNP;
        }
        if(!doneP) {
            posP += offNP;
        }
    }
    
    float dstN = horzSpan ? pos.x - posN.x : pos.y - posN.y;
    float dstP = horzSpan ? posP.x - pos.x : posP.y - pos.y;
    bool directionN = dstN < dstP;
    lumaEndN = directionN ? lumaEndN : lumaEndP;
    
    if(((lumaM - lumaN) < 0.0) == ((lumaEndN - lumaN) < 0.0)) {
        lengthSign = 0.0;
    }
 
    float spanLength = (dstP + dstN);
    dstN = directionN ? dstN : dstP;
    float subPixelOffset = (0.5 + (dstN * (-1.0/spanLength))) * lengthSign;
    vec3 rgbF = texture(tex, vec2(
        pos.x + (horzSpan ? 0.0 : subPixelOffset),
        pos.y + (horzSpan ? subPixelOffset : 0.0))).xyz;
    return FxaaLerp3(rgbL, rgbF, blendL); 
}

vec4 hook() {
    // Calculate frame size reciprocal
    vec2 rcpFrame = vec2(1.0) / HOOKED_size;
    
    // Run FXAA pixel shader
    vec3 color = FxaaPixelShader(HOOKED_pos, HOOKED_raw, rcpFrame);
    
    return vec4(color, 1.0);
}