/**
 * Copyright (C) 2013 Jorge Jimenez (jorge@iryoku.com)
 * Copyright (C) 2013 Jose I. Echevarria (joseignacioechevarria@gmail.com)
 * Copyright (C) 2013 Belen Masia (bmasia@unizar.es)
 * Copyright (C) 2013 Fernando Navarro (fernandn@microsoft.com)
 * Copyright (C) 2013 Diego Gutierrez (diegog@unizar.es)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is furnished to
 * do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software. As clarification, there
 * is no requirement that the copyright notice and permission be included in
 * binary distributions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */


//-----------------------------------------------------------------------------
// Edge Detection Pixel Shaders (First Pass)

/**
 * Luma Edge Detection
 *
 * IMPORTANT NOTICE: luma edge detection requires gamma-corrected colors, and
 * thus 'colorTex' should be a non-sRGB texture.
 */
float2 SMAALumaEdgeDetectionPS(float2 texcoord,
                               float4 offset[3],
                               SMAATexture2D(colorTex)
                               #if SMAA_PREDICATION
                               , SMAATexture2D(predicationTex)
                               #endif
                               ) {
    // Calculate the threshold:
    #if SMAA_PREDICATION
    float2 threshold = SMAACalculatePredicatedThreshold(texcoord, offset, SMAATexturePass2D(predicationTex));
    #else
    float2 threshold = float2(SMAA_THRESHOLD, SMAA_THRESHOLD);
    #endif

    // Calculate lumas:
    float3 weights = float3(0.2126, 0.7152, 0.0722);
    float L = dot(SMAASamplePoint(colorTex, texcoord).rgb, weights);

    float Lleft = dot(SMAASamplePoint(colorTex, offset[0].xy).rgb, weights);
    float Ltop  = dot(SMAASamplePoint(colorTex, offset[0].zw).rgb, weights);

    // We do the usual threshold:
    float4 delta;
    delta.xy = abs(L - float2(Lleft, Ltop));
    float2 edges = step(threshold, delta.xy);

    // Then discard if there is no edge:
    if (dot(edges, float2(1.0, 1.0)) == 0.0)
        discard;

    // Calculate right and bottom deltas:
    float Lright = dot(SMAASamplePoint(colorTex, offset[1].xy).rgb, weights);
    float Lbottom  = dot(SMAASamplePoint(colorTex, offset[1].zw).rgb, weights);
    delta.zw = abs(L - float2(Lright, Lbottom));

    // Calculate the maximum delta in the direct neighborhood:
    float2 maxDelta = max(delta.xy, delta.zw);

    // Calculate left-left and top-top deltas:
    float Lleftleft = dot(SMAASamplePoint(colorTex, offset[2].xy).rgb, weights);
    float Ltoptop = dot(SMAASamplePoint(colorTex, offset[2].zw).rgb, weights);
    delta.zw = abs(float2(Lleft, Ltop) - float2(Lleftleft, Ltoptop));

    // Calculate the final maximum delta:
    maxDelta = max(maxDelta.xy, delta.zw);
    float finalDelta = max(maxDelta.x, maxDelta.y);

    // Local contrast adaptation:
    edges.xy *= step(finalDelta, SMAA_LOCAL_CONTRAST_ADAPTATION_FACTOR * delta.xy);

    return edges;
}

/**
 * Color Edge Detection
 *
 * IMPORTANT NOTICE: color edge detection requires gamma-corrected colors, and
 * thus 'colorTex' should be a non-sRGB texture.
 */
float2 SMAAColorEdgeDetectionPS(float2 texcoord,
                                float4 offset[3],
                                SMAATexture2D(colorTex)
                                #if SMAA_PREDICATION
                                , SMAATexture2D(predicationTex)
                                #endif
                                ) {
    // Calculate the threshold:
    #if SMAA_PREDICATION
    float2 threshold = SMAACalculatePredicatedThreshold(texcoord, offset, predicationTex);
    #else
    float2 threshold = float2(SMAA_THRESHOLD, SMAA_THRESHOLD);
    #endif

    // Calculate color deltas:
    float4 delta;
    float3 C = SMAASamplePoint(colorTex, texcoord).rgb;

    float3 Cleft = SMAASamplePoint(colorTex, offset[0].xy).rgb;
    float3 t = abs(C - Cleft);
    delta.x = max(max(t.r, t.g), t.b);

    float3 Ctop  = SMAASamplePoint(colorTex, offset[0].zw).rgb;
    t = abs(C - Ctop);
    delta.y = max(max(t.r, t.g), t.b);

    // We do the usual threshold:
    float2 edges = step(threshold, delta.xy);

    // Then discard if there is no edge:
    if (dot(edges, float2(1.0, 1.0)) == 0.0)
        discard;

    // Calculate right and bottom deltas:
    float3 Cright = SMAASamplePoint(colorTex, offset[1].xy).rgb;
    t = abs(C - Cright);
    delta.z = max(max(t.r, t.g), t.b);

    float3 Cbottom  = SMAASamplePoint(colorTex, offset[1].zw).rgb;
    t = abs(C - Cbottom);
    delta.w = max(max(t.r, t.g), t.b);

    // Calculate the maximum delta in the direct neighborhood:
    float2 maxDelta = max(delta.xy, delta.zw);

    // Calculate left-left and top-top deltas:
    float3 Cleftleft  = SMAASamplePoint(colorTex, offset[2].xy).rgb;
    t = abs(C - Cleftleft);
    delta.z = max(max(t.r, t.g), t.b);

    float3 Ctoptop = SMAASamplePoint(colorTex, offset[2].zw).rgb;
    t = abs(C - Ctoptop);
    delta.w = max(max(t.r, t.g), t.b);

    // Calculate the final maximum delta:
    maxDelta = max(maxDelta.xy, delta.zw);
    float finalDelta = max(maxDelta.x, maxDelta.y);

    // Local contrast adaptation:
    edges.xy *= step(finalDelta, SMAA_LOCAL_CONTRAST_ADAPTATION_FACTOR * delta.xy);

    return edges;
}

/**
 * Depth Edge Detection
 */
float2 SMAADepthEdgeDetectionPS(float2 texcoord,
                                float4 offset[3],
                                SMAATexture2D(depthTex)) {
    float3 neighbours = SMAAGatherNeighbours(texcoord, offset, SMAATexturePass2D(depthTex));
    float2 delta = abs(neighbours.xx - float2(neighbours.y, neighbours.z));
    float2 edges = step(SMAA_DEPTH_THRESHOLD, delta);

    if (dot(edges, float2(1.0, 1.0)) == 0.0)
        discard;

    return edges;
}

//-----------------------------------------------------------------------------
// Diagonal Search Functions

#if !defined(SMAA_DISABLE_DIAG_DETECTION)

/**
 * Allows to decode two binary values from a bilinear-filtered access.
 */
float2 SMAADecodeDiagBilinearAccess(float2 e) {
    // Bilinear access for fetching 'e' have a 0.25 offset, and we are
    // interested in the R and G edges:
    //
    // +---G---+-------+
    // |   x o R   x   |
    // +-------+-------+
    //
    // Then, if one of these edge is enabled:
    //   Red:   (0.75 * X + 0.25 * 1) => 0.25 or 1.0
    //   Green: (0.75 * 1 + 0.25 * X) => 0.75 or 1.0
    //
    // This function will unpack the values (mad + mul + round):
    // wolframalpha.com: round(x * abs(5 * x - 5 * 0.75)) plot 0 to 1
    e.r = e.r * abs(5.0 * e.r - 5.0 * 0.75);
    return round(e);
}

float4 SMAADecodeDiagBilinearAccess(float4 e) {
    e.rb = e.rb * abs(5.0 * e.rb - 5.0 * 0.75);
    return round(e);
}

/**
 * These functions allows to perform diagonal pattern searches.
 */
float2 SMAASearchDiag1(SMAATexture2D(edgesTex), float2 texcoord, float2 dir, out float2 e) {
    float4 coord = float4(texcoord, -1.0, 1.0);
    float3 t = float3(SMAA_RT_METRICS.xy, 1.0);
    while (coord.z < float(SMAA_MAX_SEARCH_STEPS_DIAG - 1) &&
           coord.w > 0.9) {
        coord.xyz = mad(t, float3(dir, 1.0), coord.xyz);
        e = SMAASampleLevelZero(edgesTex, coord.xy).rg;
        coord.w = dot(e, float2(0.5, 0.5));
    }
    return coord.zw;
}

float2 SMAASearchDiag2(SMAATexture2D(edgesTex), float2 texcoord, float2 dir, out float2 e) {
    float4 coord = float4(texcoord, -1.0, 1.0);
    coord.x += 0.25 * SMAA_RT_METRICS.x; // See @SearchDiag2Optimization
    float3 t = float3(SMAA_RT_METRICS.xy, 1.0);
    while (coord.z < float(SMAA_MAX_SEARCH_STEPS_DIAG - 1) &&
           coord.w > 0.9) {
        coord.xyz = mad(t, float3(dir, 1.0), coord.xyz);

        // @SearchDiag2Optimization
        // Fetch both edges at once using bilinear filtering:
        e = SMAASampleLevelZero(edgesTex, coord.xy).rg;
        e = SMAADecodeDiagBilinearAccess(e);

        // Non-optimized version:
        // e.g = SMAASampleLevelZero(edgesTex, coord.xy).g;
        // e.r = SMAASampleLevelZeroOffset(edgesTex, coord.xy, int2(1, 0)).r;

        coord.w = dot(e, float2(0.5, 0.5));
    }
    return coord.zw;
}

/** 
 * Similar to SMAAArea, this calculates the area corresponding to a certain
 * diagonal distance and crossing edges 'e'.
 */
float2 SMAAAreaDiag(SMAATexture2D(areaTex), float2 dist, float2 e, float offset) {
    float2 texcoord = mad(float2(SMAA_AREATEX_MAX_DISTANCE_DIAG, SMAA_AREATEX_MAX_DISTANCE_DIAG), e, dist);

    // We do a scale and bias for mapping to texel space:
    texcoord = mad(SMAA_AREATEX_PIXEL_SIZE, texcoord, 0.5 * SMAA_AREATEX_PIXEL_SIZE);

    // Diagonal areas are on the second half of the texture:
    texcoord.x += 0.5;

    // Move to proper place, according to the subpixel offset:
    texcoord.y += SMAA_AREATEX_SUBTEX_SIZE * offset;

    // Do it!
    return SMAA_AREATEX_SELECT(SMAASampleLevelZero(areaTex, texcoord));
}

/**
 * This searches for diagonal patterns and returns the corresponding weights.
 */
float2 SMAACalculateDiagWeights(SMAATexture2D(edgesTex), SMAATexture2D(areaTex), float2 texcoord, float2 e, float4 subsampleIndices) {
    float2 weights = float2(0.0, 0.0);

    // Search for the line ends:
    float4 d;
    float2 end;
    if (e.r > 0.0) {
        d.xz = SMAASearchDiag1(SMAATexturePass2D(edgesTex), texcoord, float2(-1.0,  1.0), end);
        d.x += float(end.y > 0.9);
    } else
        d.xz = float2(0.0, 0.0);
    d.yw = SMAASearchDiag1(SMAATexturePass2D(edgesTex), texcoord, float2(1.0, -1.0), end);

    SMAA_BRANCH
    if (d.x + d.y > 2.0) { // d.x + d.y + 1 > 3
        // Fetch the crossing edges:
        float4 coords = mad(float4(-d.x + 0.25, d.x, d.y, -d.y - 0.25), SMAA_RT_METRICS.xyxy, texcoord.xyxy);
        float4 c;
        c.xy = SMAASampleLevelZeroOffset(edgesTex, coords.xy, int2(-1,  0)).rg;
        c.zw = SMAASampleLevelZeroOffset(edgesTex, coords.zw, int2( 1,  0)).rg;
        c.yxwz = SMAADecodeDiagBilinearAccess(c.xyzw);

        // Non-optimized version:
        // float4 coords = mad(float4(-d.x, d.x, d.y, -d.y), SMAA_RT_METRICS.xyxy, texcoord.xyxy);
        // float4 c;
        // c.x = SMAASampleLevelZeroOffset(edgesTex, coords.xy, int2(-1,  0)).g;
        // c.y = SMAASampleLevelZeroOffset(edgesTex, coords.xy, int2( 0,  0)).r;
        // c.z = SMAASampleLevelZeroOffset(edgesTex, coords.zw, int2( 1,  0)).g;
        // c.w = SMAASampleLevelZeroOffset(edgesTex, coords.zw, int2( 1, -1)).r;

        // Merge crossing edges at each side into a single value:
        float2 cc = mad(float2(2.0, 2.0), c.xz, c.yw);

        // Remove the crossing edge if we didn't found the end of the line:
        SMAAMovc(bool2(step(0.9, d.zw)), cc, float2(0.0, 0.0));

        // Fetch the areas for this line:
        weights += SMAAAreaDiag(SMAATexturePass2D(areaTex), d.xy, cc, subsampleIndices.z);
    }

    // Search for the line ends:
    d.xz = SMAASearchDiag2(SMAATexturePass2D(edgesTex), texcoord, float2(-1.0, -1.0), end);
    if (SMAASampleLevelZeroOffset(edgesTex, texcoord, int2(1, 0)).r > 0.0) {
        d.yw = SMAASearchDiag2(SMAATexturePass2D(edgesTex), texcoord, float2(1.0, 1.0), end);
        d.y += float(end.y > 0.9);
    } else
        d.yw = float2(0.0, 0.0);

    SMAA_BRANCH
    if (d.x + d.y > 2.0) { // d.x + d.y + 1 > 3
        // Fetch the crossing edges:
        float4 coords = mad(float4(-d.x, -d.x, d.y, d.y), SMAA_RT_METRICS.xyxy, texcoord.xyxy);
        float4 c;
        c.x  = SMAASampleLevelZeroOffset(edgesTex, coords.xy, int2(-1,  0)).g;
        c.y  = SMAASampleLevelZeroOffset(edgesTex, coords.xy, int2( 0, -1)).r;
        c.zw = SMAASampleLevelZeroOffset(edgesTex, coords.zw, int2( 1,  0)).gr;
        float2 cc = mad(float2(2.0, 2.0), c.xz, c.yw);

        // Remove the crossing edge if we didn't found the end of the line:
        SMAAMovc(bool2(step(0.9, d.zw)), cc, float2(0.0, 0.0));

        // Fetch the areas for this line:
        weights += SMAAAreaDiag(SMAATexturePass2D(areaTex), d.xy, cc, subsampleIndices.w).gr;
    }

    return weights;
}
#endif

//-----------------------------------------------------------------------------
// Horizontal/Vertical Search Functions

/**
 * This allows to determine how much length should we add in the last step
 * of the searches. It takes the bilinearly interpolated edge (see 
 * @PSEUDO_GATHER4), and adds 0, 1 or 2, depending on which edges and
 * crossing edges are active.
 */
float SMAASearchLength(SMAATexture2D(searchTex), float2 e, float offset) {
    // The texture is flipped vertically, with left and right cases taking half
    // of the space horizontally:
    float2 scale = SMAA_SEARCHTEX_SIZE * float2(0.5, -1.0);
    float2 bias = SMAA_SEARCHTEX_SIZE * float2(offset, 1.0);

    // Scale and bias to access texel centers:
    scale += float2(-1.0,  1.0);
    bias  += float2( 0.5, -0.5);

    // Convert from pixel coordinates to texcoords:
    // (We use SMAA_SEARCHTEX_PACKED_SIZE because the texture is cropped)
    scale *= 1.0 / SMAA_SEARCHTEX_PACKED_SIZE;
    bias *= 1.0 / SMAA_SEARCHTEX_PACKED_SIZE;

    // Lookup the search texture:
    return SMAA_SEARCHTEX_SELECT(SMAASampleLevelZero(searchTex, mad(scale, e, bias)));
}

/**
 * Horizontal/vertical search functions for the 2nd pass.
 */
float SMAASearchXLeft(SMAATexture2D(edgesTex), SMAATexture2D(searchTex), float2 texcoord, float end) {
    /**
     * @PSEUDO_GATHER4
     * This texcoord has been offset by (-0.25, -0.125) in the vertex shader to
     * sample between edge, thus fetching four edges in a row.
     * Sampling with different offsets in each direction allows to disambiguate
     * which edges are active from the four fetched ones.
     */
    float2 e = float2(0.0, 1.0);
    while (texcoord.x > end && 
           e.g > 0.8281 && // Is there some edge not activated?
           e.r == 0.0) { // Or is there a crossing edge that breaks the line?
        e = SMAASampleLevelZero(edgesTex, texcoord).rg;
        texcoord = mad(-float2(2.0, 0.0), SMAA_RT_METRICS.xy, texcoord);
    }

    float offset = mad(-(255.0 / 127.0), SMAASearchLength(SMAATexturePass2D(searchTex), e, 0.0), 3.25);
    return mad(SMAA_RT_METRICS.x, offset, texcoord.x);

    // Non-optimized version:
    // We correct the previous (-0.25, -0.125) offset we applied:
    // texcoord.x += 0.25 * SMAA_RT_METRICS.x;

    // The searches are bias by 1, so adjust the coords accordingly:
    // texcoord.x += SMAA_RT_METRICS.x;

    // Disambiguate the length added by the last step:
    // texcoord.x += 2.0 * SMAA_RT_METRICS.x; // Undo last step
    // texcoord.x -= SMAA_RT_METRICS.x * (255.0 / 127.0) * SMAASearchLength(SMAATexturePass2D(searchTex), e, 0.0);
    // return mad(SMAA_RT_METRICS.x, offset, texcoord.x);
}

float SMAASearchXRight(SMAATexture2D(edgesTex), SMAATexture2D(searchTex), float2 texcoord, float end) {
    float2 e = float2(0.0, 1.0);
    while (texcoord.x < end && 
           e.g > 0.8281 && // Is there some edge not activated?
           e.r == 0.0) { // Or is there a crossing edge that breaks the line?
        e = SMAASampleLevelZero(edgesTex, texcoord).rg;
        texcoord = mad(float2(2.0, 0.0), SMAA_RT_METRICS.xy, texcoord);
    }
    float offset = mad(-(255.0 / 127.0), SMAASearchLength(SMAATexturePass2D(searchTex), e, 0.5), 3.25);
    return mad(-SMAA_RT_METRICS.x, offset, texcoord.x);
}

float SMAASearchYUp(SMAATexture2D(edgesTex), SMAATexture2D(searchTex), float2 texcoord, float end) {
    float2 e = float2(1.0, 0.0);
    while (texcoord.y > end && 
           e.r > 0.8281 && // Is there some edge not activated?
           e.g == 0.0) { // Or is there a crossing edge that breaks the line?
        e = SMAASampleLevelZero(edgesTex, texcoord).rg;
        texcoord = mad(-float2(0.0, 2.0), SMAA_RT_METRICS.xy, texcoord);
    }
    float offset = mad(-(255.0 / 127.0), SMAASearchLength(SMAATexturePass2D(searchTex), e.gr, 0.0), 3.25);
    return mad(SMAA_RT_METRICS.y, offset, texcoord.y);
}

float SMAASearchYDown(SMAATexture2D(edgesTex), SMAATexture2D(searchTex), float2 texcoord, float end) {
    float2 e = float2(1.0, 0.0);
    while (texcoord.y < end && 
           e.r > 0.8281 && // Is there some edge not activated?
           e.g == 0.0) { // Or is there a crossing edge that breaks the line?
        e = SMAASampleLevelZero(edgesTex, texcoord).rg;
        texcoord = mad(float2(0.0, 2.0), SMAA_RT_METRICS.xy, texcoord);
    }
    float offset = mad(-(255.0 / 127.0), SMAASearchLength(SMAATexturePass2D(searchTex), e.gr, 0.5), 3.25);
    return mad(-SMAA_RT_METRICS.y, offset, texcoord.y);
}

/** 
 * Ok, we have the distance and both crossing edges. So, what are the areas
 * at each side of current edge?
 */
float2 SMAAArea(SMAATexture2D(areaTex), float2 dist, float e1, float e2, float offset) {
    // Rounding prevents precision errors of bilinear filtering:
    float2 texcoord = mad(float2(SMAA_AREATEX_MAX_DISTANCE, SMAA_AREATEX_MAX_DISTANCE), round(4.0 * float2(e1, e2)), dist);
    
    // We do a scale and bias for mapping to texel space:
    texcoord = mad(SMAA_AREATEX_PIXEL_SIZE, texcoord, 0.5 * SMAA_AREATEX_PIXEL_SIZE);

    // Move to proper place, according to the subpixel offset:
    texcoord.y = mad(SMAA_AREATEX_SUBTEX_SIZE, offset, texcoord.y);

    // Do it!
    return SMAA_AREATEX_SELECT(SMAASampleLevelZero(areaTex, texcoord));
}

//-----------------------------------------------------------------------------
// Corner Detection Functions

void SMAADetectHorizontalCornerPattern(SMAATexture2D(edgesTex), inout float2 weights, float4 texcoord, float2 d) {
    #if !defined(SMAA_DISABLE_CORNER_DETECTION)
    float2 leftRight = step(d.xy, d.yx);
    float2 rounding = (1.0 - SMAA_CORNER_ROUNDING_NORM) * leftRight;

    rounding /= leftRight.x + leftRight.y; // Reduce blending for pixels in the center of a line.

    float2 factor = float2(1.0, 1.0);
    factor.x -= rounding.x * SMAASampleLevelZeroOffset(edgesTex, texcoord.xy, int2(0,  1)).r;
    factor.x -= rounding.y * SMAASampleLevelZeroOffset(edgesTex, texcoord.zw, int2(1,  1)).r;
    factor.y -= rounding.x * SMAASampleLevelZeroOffset(edgesTex, texcoord.xy, int2(0, -2)).r;
    factor.y -= rounding.y * SMAASampleLevelZeroOffset(edgesTex, texcoord.zw, int2(1, -2)).r;

    weights *= saturate(factor);
    #endif
}

void SMAADetectVerticalCornerPattern(SMAATexture2D(edgesTex), inout float2 weights, float4 texcoord, float2 d) {
    #if !defined(SMAA_DISABLE_CORNER_DETECTION)
    float2 leftRight = step(d.xy, d.yx);
    float2 rounding = (1.0 - SMAA_CORNER_ROUNDING_NORM) * leftRight;

    rounding /= leftRight.x + leftRight.y;

    float2 factor = float2(1.0, 1.0);
    factor.x -= rounding.x * SMAASampleLevelZeroOffset(edgesTex, texcoord.xy, int2( 1, 0)).g;
    factor.x -= rounding.y * SMAASampleLevelZeroOffset(edgesTex, texcoord.zw, int2( 1, 1)).g;
    factor.y -= rounding.x * SMAASampleLevelZeroOffset(edgesTex, texcoord.xy, int2(-2, 0)).g;
    factor.y -= rounding.y * SMAASampleLevelZeroOffset(edgesTex, texcoord.zw, int2(-2, 1)).g;

    weights *= saturate(factor);
    #endif
}

//-----------------------------------------------------------------------------
// Blending Weight Calculation Pixel Shader (Second Pass)

float4 SMAABlendingWeightCalculationPS(float2 texcoord,
                                       float2 pixcoord,
                                       float4 offset[3],
                                       SMAATexture2D(edgesTex),
                                       SMAATexture2D(areaTex),
                                       SMAATexture2D(searchTex),
                                       float4 subsampleIndices) { // Just pass zero for SMAA 1x, see @SUBSAMPLE_INDICES.
    float4 weights = float4(0.0, 0.0, 0.0, 0.0);

    float2 e = SMAASample(edgesTex, texcoord).rg;

    SMAA_BRANCH
    if (e.g > 0.0) { // Edge at north
        #if !defined(SMAA_DISABLE_DIAG_DETECTION)
        // Diagonals have both north and west edges, so searching for them in
        // one of the boundaries is enough.
        weights.rg = SMAACalculateDiagWeights(SMAATexturePass2D(edgesTex), SMAATexturePass2D(areaTex), texcoord, e, subsampleIndices);

        // We give priority to diagonals, so if we find a diagonal we skip 
        // horizontal/vertical processing.
        SMAA_BRANCH
        if (weights.r == -weights.g) { // weights.r + weights.g == 0.0
        #endif

        float2 d;

        // Find the distance to the left:
        float3 coords;
        coords.x = SMAASearchXLeft(SMAATexturePass2D(edgesTex), SMAATexturePass2D(searchTex), offset[0].xy, offset[2].x);
        coords.y = offset[1].y; // offset[1].y = texcoord.y - 0.25 * SMAA_RT_METRICS.y (@CROSSING_OFFSET)
        d.x = coords.x;

        // Now fetch the left crossing edges, two at a time using bilinear
        // filtering. Sampling at -0.25 (see @CROSSING_OFFSET) enables to
        // discern what value each edge has:
        float e1 = SMAASampleLevelZero(edgesTex, coords.xy).r;

        // Find the distance to the right:
        coords.z = SMAASearchXRight(SMAATexturePass2D(edgesTex), SMAATexturePass2D(searchTex), offset[0].zw, offset[2].y);
        d.y = coords.z;

        // We want the distances to be in pixel units (doing this here allow to
        // better interleave arithmetic and memory accesses):
        d = abs(round(mad(SMAA_RT_METRICS.zz, d, -pixcoord.xx)));

        // SMAAArea below needs a sqrt, as the areas texture is compressed
        // quadratically:
        float2 sqrt_d = sqrt(d);

        // Fetch the right crossing edges:
        float e2 = SMAASampleLevelZeroOffset(edgesTex, coords.zy, int2(1, 0)).r;

        // Ok, we know how this pattern looks like, now it is time for getting
        // the actual area:
        weights.rg = SMAAArea(SMAATexturePass2D(areaTex), sqrt_d, e1, e2, subsampleIndices.y);

        // Fix corners:
        coords.y = texcoord.y;
        SMAADetectHorizontalCornerPattern(SMAATexturePass2D(edgesTex), weights.rg, coords.xyzy, d);

        #if !defined(SMAA_DISABLE_DIAG_DETECTION)
        } else
            e.r = 0.0; // Skip vertical processing.
        #endif
    }

    SMAA_BRANCH
    if (e.r > 0.0) { // Edge at west
        float2 d;

        // Find the distance to the top:
        float3 coords;
        coords.y = SMAASearchYUp(SMAATexturePass2D(edgesTex), SMAATexturePass2D(searchTex), offset[1].xy, offset[2].z);
        coords.x = offset[0].x; // offset[1].x = texcoord.x - 0.25 * SMAA_RT_METRICS.x;
        d.x = coords.y;

        // Fetch the top crossing edges:
        float e1 = SMAASampleLevelZero(edgesTex, coords.xy).g;

        // Find the distance to the bottom:
        coords.z = SMAASearchYDown(SMAATexturePass2D(edgesTex), SMAATexturePass2D(searchTex), offset[1].zw, offset[2].w);
        d.y = coords.z;

        // We want the distances to be in pixel units:
        d = abs(round(mad(SMAA_RT_METRICS.ww, d, -pixcoord.yy)));

        // SMAAArea below needs a sqrt, as the areas texture is compressed 
        // quadratically:
        float2 sqrt_d = sqrt(d);

        // Fetch the bottom crossing edges:
        float e2 = SMAASampleLevelZeroOffset(edgesTex, coords.xz, int2(0, 1)).g;

        // Get the area for this direction:
        weights.ba = SMAAArea(SMAATexturePass2D(areaTex), sqrt_d, e1, e2, subsampleIndices.x);

        // Fix corners:
        coords.x = texcoord.x;
        SMAADetectVerticalCornerPattern(SMAATexturePass2D(edgesTex), weights.ba, coords.xyxz, d);
    }

    return weights;
}

//-----------------------------------------------------------------------------
// Neighborhood Blending Pixel Shader (Third Pass)

float4 SMAANeighborhoodBlendingPS(float2 texcoord,
                                  float4 offset,
                                  SMAATexture2D(colorTex),
                                  SMAATexture2D(blendTex)
                                  #if SMAA_REPROJECTION
                                  , SMAATexture2D(velocityTex)
                                  #endif
                                  ) {
    // Fetch the blending weights for current pixel:
    float4 a;
    a.x = SMAASample(blendTex, offset.xy).a; // Right
    a.y = SMAASample(blendTex, offset.zw).g; // Top
    a.wz = SMAASample(blendTex, texcoord).xz; // Bottom / Left

    // Is there any blending weight with a value greater than 0.0?
    SMAA_BRANCH
    if (dot(a, float4(1.0, 1.0, 1.0, 1.0)) < 1e-5) {
        float4 color = SMAASampleLevelZero(colorTex, texcoord);

        #if SMAA_REPROJECTION
        float2 velocity = SMAA_DECODE_VELOCITY(SMAASampleLevelZero(velocityTex, texcoord));

        // Pack velocity into the alpha channel:
        color.a = sqrt(5.0 * length(velocity));
        #endif

        return color;
    } else {
        bool h = max(a.x, a.z) > max(a.y, a.w); // max(horizontal) > max(vertical)

        // Calculate the blending offsets:
        float4 blendingOffset = float4(0.0, a.y, 0.0, a.w);
        float2 blendingWeight = a.yw;
        SMAAMovc(bool4(h, h, h, h), blendingOffset, float4(a.x, 0.0, a.z, 0.0));
        SMAAMovc(bool2(h, h), blendingWeight, a.xz);
        blendingWeight /= dot(blendingWeight, float2(1.0, 1.0));

        // Calculate the texture coordinates:
        float4 blendingCoord = mad(blendingOffset, float4(SMAA_RT_METRICS.xy, -SMAA_RT_METRICS.xy), texcoord.xyxy);

        // We exploit bilinear filtering to mix current pixel with the chosen
        // neighbor:
        float4 color = blendingWeight.x * SMAASampleLevelZero(colorTex, blendingCoord.xy);
        color += blendingWeight.y * SMAASampleLevelZero(colorTex, blendingCoord.zw);

        #if SMAA_REPROJECTION
        // Antialias velocity for proper reprojection in a later stage:
        float2 velocity = blendingWeight.x * SMAA_DECODE_VELOCITY(SMAASampleLevelZero(velocityTex, blendingCoord.xy));
        velocity += blendingWeight.y * SMAA_DECODE_VELOCITY(SMAASampleLevelZero(velocityTex, blendingCoord.zw));

        // Pack velocity into the alpha channel:
        color.a = sqrt(5.0 * length(velocity));
        #endif

        return color;
    }
}

//-----------------------------------------------------------------------------
// Temporal Resolve Pixel Shader (Optional Pass)

float4 SMAAResolvePS(float2 texcoord,
                     SMAATexture2D(currentColorTex),
                     SMAATexture2D(previousColorTex)
                     #if SMAA_REPROJECTION
                     , SMAATexture2D(velocityTex)
                     #endif
                     ) {
    #if SMAA_REPROJECTION
    // Velocity is assumed to be calculated for motion blur, so we need to
    // inverse it for reprojection:
    float2 velocity = -SMAA_DECODE_VELOCITY(SMAASamplePoint(velocityTex, texcoord).rg);

    // Fetch current pixel:
    float4 current = SMAASamplePoint(currentColorTex, texcoord);

    // Reproject current coordinates and fetch previous pixel:
    float4 previous = SMAASamplePoint(previousColorTex, texcoord + velocity);

    // Attenuate the previous pixel if the velocity is different:
    float delta = abs(current.a * current.a - previous.a * previous.a) / 5.0;
    float weight = 0.5 * saturate(1.0 - sqrt(delta) * SMAA_REPROJECTION_WEIGHT_SCALE);

    // Blend the pixels according to the calculated weight:
    return lerp(current, previous, weight);
    #else
    // Just blend the pixels:
    float4 current = SMAASamplePoint(currentColorTex, texcoord);
    float4 previous = SMAASamplePoint(previousColorTex, texcoord);
    return lerp(current, previous, 0.5);
    #endif
}

//-----------------------------------------------------------------------------
// Separate Multisamples Pixel Shader (Optional Pass)

#ifdef SMAALoad
void SMAASeparatePS(float4 position,
                    float2 texcoord,
                    out float4 target0,
                    out float4 target1,
                    SMAATexture2DMS2(colorTexMS)) {
    int2 pos = int2(position.xy);
    target0 = SMAALoad(colorTexMS, pos, 0);
    target1 = SMAALoad(colorTexMS, pos, 1);
}
#endif

//-----------------------------------------------------------------------------