    /*
        CRT-interlaced-halation shader - pass2

        Like the CRT-interlaced shader, but adds a subtle glow around bright areas
        of the screen.

        Copyright (C) 2010-2012 cgwg, Themaister and DOLLS

        This program is free software; you can redistribute it and/or modify it
        under the terms of the GNU General Public License as published by the Free
        Software Foundation; either version 2 of the License, or (at your option)
        any later version.

        (cgwg gave their consent to have the original version of this shader
        distributed under the GPL in this message:

            http://board.byuu.org/viewtopic.php?p=26075#p26075

            "Feel free to distribute my shaders under the GPL. After all, the
            barrel distortion code was taken from the Curvature shader, which is
            under the GPL."
        )
    */
#ifdef GL_ES
precision highp float;
#endif

            // Comment the next line to disable interpolation in linear gamma (and
            // gain speed).
            #define LINEAR_PROCESSING

            // Enable screen curvature.
            #define CURVATURE

            // Enable 3x oversampling of the beam profile
            //#define OVERSAMPLE

            // Use the older, purely gaussian beam profile
            #define USEGAUSSIAN
          
            // Use interlacing detection; may interfere with other shaders if combined
            #define INTERLACED
         
         // Enable Dot-mask emulation:
            // Output pixels are alternately tinted green and magenta.
         //#define DOTMASK
         
         //Enable if using several shaders. 
         //Disabling it reduces moire for single pass.
         #define MULTIPASS
         
            // Macros.
            #define FIX(c) max(abs(c), 1e-5);
            #define PI 3.141592653589

            #ifdef LINEAR_PROCESSING
            #       define TEX2D(c) pow(COMPAT_TEXTURE(OrigTexture, (c)), vec4(CRTgamma))
            #else
            #       define TEX2D(c) COMPAT_TEXTURE(OrigTexture, (c))
            #endif



                    // START of parameters

                    // gamma of simulated CRT
                    float CRTgamma = 2.4;
                    // gamma of display monitor (typically 2.2 is correct)
                    float monitorgamma = 2.2;
                    // overscan (e.g. 1.02 for 2% overscan)
                    vec2 overscan = vec2(1.0,1.0);
                    // aspect ratio
                    vec2 aspect = vec2(1.0, 0.75);
                    // lengths are measured in units of (approximately) the width
                    // of the monitor simulated distance from viewer to monitor
                    float d = 2.0;
                    // radius of curvature
                    float R = 2.0;
                    // tilt angle in radians
                    // (behavior might be a bit wrong if both components are
                    // nonzero)
                    const vec2 angle = vec2(0.0,0.0);
                    // size of curved corners
                    float cornersize = 0.01;
                    // border smoothness parameter
                    // decrease if borders are too aliased
                    float cornersmooth = 800.0;

                    // END of parameters


            float intersect(vec2 xy, vec2 sinangle, vec2 cosangle)
            {
                    float A = dot(xy,xy)+d*d;
                    float B = 2.0*(R*(dot(xy,sinangle)-d*cosangle.x*cosangle.y)-d*d);
                    float C = d*d + 2.0*R*d*cosangle.x*cosangle.y;
                    return (-B-sqrt(B*B-4.0*A*C))/(2.0*A);
            }

            vec2 bkwtrans(vec2 xy, vec2 sinangle, vec2 cosangle)
            {
                    float c = intersect(xy, sinangle, cosangle);
                    vec2 point = vec2(c)*xy;
                    point -= vec2(-R)*sinangle;
                    point /= vec2(R);
                    vec2 tang = sinangle/cosangle;
                    vec2 poc = point/cosangle;
                    float A = dot(tang,tang)+1.0;
                    float B = -2.0*dot(poc,tang);
                    float C = dot(poc,poc)-1.0;
                    float a = (-B+sqrt(B*B-4.0*A*C))/(2.0*A);
                    vec2 uv = (point-a*sinangle)/cosangle;
                    float r = FIX(R*acos(a));
                    return uv*r/sin(r/R);
            }

            vec2 fwtrans(vec2 uv, vec2 sinangle, vec2 cosangle)
            {
                    float r = FIX(sqrt(dot(uv,uv)));
                    uv *= sin(r/R)/r;
                    float x = 1.0-cos(r/R);
                    float D = d/R + x*cosangle.x*cosangle.y+dot(uv,sinangle);
                    return d*(uv*cosangle-x*sinangle)/D;
            }

            vec3 maxscale(vec2 sinangle, vec2 cosangle)
            {
                    vec2 c = bkwtrans(-R * sinangle / (1.0 + R/d*cosangle.x*cosangle.y), sinangle, cosangle);
                    vec2 a = vec2(0.5,0.5)*aspect;
                    vec2 lo = vec2(fwtrans(vec2(-a.x,c.y), sinangle, cosangle).x,
                                 fwtrans(vec2(c.x,-a.y), sinangle, cosangle).y)/aspect;
                    vec2 hi = vec2(fwtrans(vec2(+a.x,c.y), sinangle, cosangle).x,
                                 fwtrans(vec2(c.x,+a.y), sinangle, cosangle).y)/aspect;
                    return vec3((hi+lo)*aspect*0.5,max(hi.x-lo.x,hi.y-lo.y));
            }

            // Calculate the influence of a scanline on the current pixel.
            //
            // 'distance' is the distance in texture coordinates from the current
            // pixel to the scanline in question.
            // 'color' is the colour of the scanline at the horizontal location of
            // the current pixel.
            vec4 scanlineWeights(float distance, vec4 color)
            {
                    // "wid" controls the width of the scanline beam, for each RGB
                    // channel The "weights" lines basically specify the formula
                    // that gives you the profile of the beam, i.e. the intensity as
                    // a function of distance from the vertical center of the
                    // scanline. In this case, it is gaussian if width=2, and
                    // becomes nongaussian for larger widths. Ideally this should
                    // be normalized so that the integral across the beam is
                    // independent of its width. That is, for a narrower beam
                    // "weights" should have a higher peak at the center of the
                    // scanline than for a wider beam.
            #ifdef USEGAUSSIAN
                    vec4 wid = 0.3 + 0.1 * pow(color, vec4(3.0));
                    vec4 weights = vec4(distance / wid);
                    return 0.4 * exp(-weights * weights) / wid;
            #else
                    vec4 wid = 2.0 + 2.0 * pow(color, vec4(4.0));
                    vec4 weights = vec4(distance / 0.3);
                    return 1.4 * exp(-pow(weights * rsqrt(0.5 * wid), wid)) / (0.6 + 0.2 * wid);
            #endif
            }

#if defined(VERTEX)

#if __VERSION__ >= 130
#define COMPAT_VARYING out
#define COMPAT_ATTRIBUTE in
#define COMPAT_TEXTURE texture
#else
#define COMPAT_VARYING varying 
#define COMPAT_ATTRIBUTE attribute 
#define COMPAT_TEXTURE texture2D
#endif

#ifdef GL_ES
#define COMPAT_PRECISION mediump
#else
#define COMPAT_PRECISION
#endif

COMPAT_ATTRIBUTE vec4 VertexCoord;
COMPAT_ATTRIBUTE vec4 COLOR;
COMPAT_ATTRIBUTE vec4 TexCoord;
COMPAT_VARYING vec4 COL0;
COMPAT_VARYING vec4 TEX0;
COMPAT_VARYING vec2 one;
COMPAT_VARYING float mod_factor;
COMPAT_VARYING vec2 ilfac;
COMPAT_VARYING vec3 stretch;
COMPAT_VARYING vec2 sinangle;
COMPAT_VARYING vec2 cosangle;
 
uniform mat4 MVPMatrix;
uniform int FrameDirection;
uniform int FrameCount;
uniform COMPAT_PRECISION vec2 OutputSize;
uniform COMPAT_PRECISION vec2 TextureSize;
uniform COMPAT_PRECISION vec2 InputSize;
uniform COMPAT_PRECISION vec2 OrigInputSize;
uniform COMPAT_PRECISION vec2 OrigTextureSize;

#define vTexCoord TEX0.xy
#define SourceSize vec4(TextureSize, 1.0 / TextureSize) //either TextureSize or InputSize
#define outsize vec4(OutputSize, 1.0 / OutputSize)

void main()
{
    gl_Position = MVPMatrix * VertexCoord;
    COL0 = COLOR;
    TEX0.xy = TexCoord.xy;
                    // Precalculate a bunch of useful values we'll need in the fragment
                    // shader.
                    sinangle = sin(angle);
                    cosangle = cos(angle);
                    stretch = maxscale(sinangle, cosangle);

        #ifdef INTERLACED
                    ilfac = vec2(1.0,clamp(floor(InputSize.y/200.0),1.0,2.0));
        #else
                    ilfac = vec2(1.0,clamp(floor(InputSize.y/1000.0),1.0,2.0));
        #endif

                    // The size of one texel, in texture-coordinates.
                    one = ilfac / OrigTextureSize.xy;

                    // Resulting X pixel-coordinate of the pixel we're drawing.
                    mod_factor = vTexCoord.x * OrigTextureSize.x * outsize.x / OrigInputSize.x;

}

#elif defined(FRAGMENT)

#if __VERSION__ >= 130
#define COMPAT_VARYING in
#define COMPAT_TEXTURE texture
out vec4 FragColor;
#else
#define COMPAT_VARYING varying
#define FragColor gl_FragColor
#define COMPAT_TEXTURE texture2D
#endif

#ifdef GL_ES
#define COMPAT_PRECISION mediump
#else
#define COMPAT_PRECISION
#endif

uniform int FrameDirection;
uniform int FrameCount;
uniform COMPAT_PRECISION vec2 OutputSize;
uniform COMPAT_PRECISION vec2 TextureSize;
uniform COMPAT_PRECISION vec2 InputSize;
uniform COMPAT_PRECISION vec2 OrigInputSize;
uniform COMPAT_PRECISION vec2 OrigTextureSize;
uniform sampler2D Texture;
uniform sampler2D OrigTexture;
COMPAT_VARYING vec4 TEX0;
COMPAT_VARYING vec2 one;
COMPAT_VARYING float mod_factor;
COMPAT_VARYING vec2 ilfac;
COMPAT_VARYING vec3 stretch;
COMPAT_VARYING vec2 sinangle;
COMPAT_VARYING vec2 cosangle;

// compatibility #defines
#define Source Texture
#define vTexCoord TEX0.xy
#define texture(c, d) COMPAT_TEXTURE(c, d)
#define SourceSize vec4(TextureSize, 1.0 / TextureSize) //either TextureSize or InputSize
#define outsize vec4(OutputSize, 1.0 / OutputSize)

void main()
{
                    // Here's a helpful diagram to keep in mind while trying to
                    // understand the code:
                    //
                    //  |      |      |      |      |
                    // -------------------------------
                    //  |      |      |      |      |
                    //  |  01  |  11  |  21  |  31  | <-- current scanline
                    //  |      | @    |      |      |
                    // -------------------------------
                    //  |      |      |      |      |
                    //  |  02  |  12  |  22  |  32  | <-- next scanline
                    //  |      |      |      |      |
                    // -------------------------------
                    //  |      |      |      |      |
                    //
                    // Each character-cell represents a pixel on the output
                    // surface, "@" represents the current pixel (always somewhere
                    // in the bottom half of the current scan-line, or the top-half
                    // of the next scanline). The grid of lines represents the
                    // edges of the texels of the underlying texture.

                    // Texture coordinates of the texel containing the active pixel.
            #ifdef CURVATURE
                    vec2 cd = vTexCoord;
                    cd *= OrigTextureSize / OrigInputSize;
                    cd = (cd-vec2(0.5))*aspect*stretch.z+stretch.xy;
                    vec2 xy =  (bkwtrans(cd, sinangle, cosangle)/overscan/aspect+vec2(0.5)) * OrigInputSize / OrigTextureSize;

            #else
                    vec2 xy = vTexCoord;
            #endif
                    vec2 cd2 = xy;
                    cd2 *= OrigTextureSize / OrigInputSize;
                    cd2 = (cd2 - vec2(0.5)) * overscan + vec2(0.5);
                    cd2 = min(cd2, vec2(1.0)-cd2) * aspect;
                    vec2 cdist = vec2(cornersize);
                    cd2 = (cdist - min(cd2,cdist));
                    float dist = sqrt(dot(cd2,cd2));
                    float cval = clamp((cdist.x-dist)*cornersmooth,0.0, 1.0);

                    vec2 xy2 = ((xy*OrigTextureSize / OrigInputSize-vec2(0.5))*vec2(1.0,1.0)+vec2(0.5)) * InputSize / TextureSize;
                    // Of all the pixels that are mapped onto the texel we are
                    // currently rendering, which pixel are we currently rendering?
                    vec2 ilfloat = vec2(0.0,ilfac.y > 1.5 ? mod(float(FrameCount),2.0) : 0.0);

                    vec2 ratio_scale = (xy * SourceSize.xy - vec2(0.5) + ilfloat)/ilfac;
          
            #ifdef OVERSAMPLE
                    //float filter = fwidth(ratio_scale.y);
                    float filter = InputSize.y / outsize.y;
            #endif
                    vec2 uv_ratio = fract(ratio_scale);

                    // Snap to the center of the underlying texel.
                    xy = (floor(ratio_scale)*ilfac + vec2(0.5) - ilfloat) / SourceSize.xy;

                    // Calculate Lanczos scaling coefficients describing the effect
                    // of various neighbour texels in a scanline on the current
                    // pixel.
                    vec4 coeffs = PI * vec4(1.0 + uv_ratio.x, uv_ratio.x, 1.0 - uv_ratio.x, 2.0 - uv_ratio.x);

                    // Prevent division by zero.
                    coeffs = FIX(coeffs);

                    // Lanczos2 kernel.
                    coeffs = 2.0 * sin(coeffs) * sin(coeffs / 2.0) / (coeffs * coeffs);

                    // Normalize.
                    coeffs /= dot(coeffs, vec4(1.0));

                    // Calculate the effective colour of the current and next
                    // scanlines at the horizontal location of the current pixel,
                    // using the Lanczos coefficients above.
  vec4 col  = clamp(mat4(
			 TEX2D(xy + vec2(-one.x, 0.0)),
			 TEX2D(xy),
			 TEX2D(xy + vec2(one.x, 0.0)),
			 TEX2D(xy + vec2(2.0 * one.x, 0.0))) * coeffs,
		    0.0, 1.0);
  vec4 col2 = clamp(mat4(
			 TEX2D(xy + vec2(-one.x, one.y)),
			 TEX2D(xy + vec2(0.0, one.y)),
			 TEX2D(xy + one),
			 TEX2D(xy + vec2(2.0 * one.x, one.y))) * coeffs,
		    0.0, 1.0);


            #ifndef LINEAR_PROCESSING
                    col  = pow(col , vec4(CRTgamma));
                    col2 = pow(col2, vec4(CRTgamma));
            #endif

                    // Calculate the influence of the current and next scanlines on
                    // the current pixel.
                    vec4 weights  = scanlineWeights(uv_ratio.y, col);
                    vec4 weights2 = scanlineWeights(1.0 - uv_ratio.y, col2);
            #ifdef OVERSAMPLE
                    uv_ratio.y =uv_ratio.y+1.0/3.0*filter;
                    weights = (weights+scanlineWeights(uv_ratio.y, col))/3.0;
                    weights2=(weights2+scanlineWeights(abs(1.0-uv_ratio.y), col2))/3.0;
                    uv_ratio.y =uv_ratio.y-2.0/3.0*filter;
                    weights=weights+scanlineWeights(abs(uv_ratio.y), col)/3.0;
                    weights2=weights2+scanlineWeights(abs(1.0-uv_ratio.y), col2)/3.0;
            #endif
                    vec3 mul_res  = (col * weights + col2 * weights2).rgb;
         #ifdef MULTIPASS
               mul_res += pow(COMPAT_TEXTURE(Source, xy2).rgb, vec3(monitorgamma))*0.1;
         #endif
               mul_res *= vec3(cval);

                    // dot-mask emulation:
                    // Output pixels are alternately tinted green and magenta.
         #ifdef DOTMASK
                    vec3 dotMaskWeights = mix(
                            vec3(1.0, 0.7, 1.0),
                            vec3(0.7, 1.0, 0.7),
                            floor(mod(mod_factor, 2.0))
                        );
            #else
                    vec3 dotMaskWeights = mix(
                            vec3(1.0, 1.0, 1.0),
                            vec3(1.0, 1.0, 1.0),
                            floor(mod(mod_factor, 2.0)));
            #endif
                    

                    mul_res *= dotMaskWeights;

                    // Convert the image gamma for display on our output device.
                    mul_res = pow(mul_res, vec3(1.0 / monitorgamma));

                    // Color the texel.
   FragColor = vec4(mul_res, 1.0);
} 
#endif
