slang-shaders/crt/shaders/crt-lottes-multipass/crt-lottes-multipass.slang

#version 450

// -- config  -- //

#define hardScan -8.0
#define warpX 0.031
#define warpY 0.041
#define maskDark 0.5
#define maskLight 1.5
#define shadowMask 1
#define brightboost 1
#define bloomAmount 1.0/16.0
#define hardBloomScan -2.0
#define shape 2.0

#define DO_BLOOM

layout(std140, set = 0, binding = 0) uniform UBO
{
   mat4 MVP;
   vec4 OutputSize;
   vec4 OriginalSize;
   vec4 SourceSize;
} global;

#pragma stage vertex
layout(location = 0) in vec4 Position;
layout(location = 1) in vec2 TexCoord;
layout(location = 0) out vec2 vTexCoord;

void main()
{
   gl_Position = global.MVP * Position;
   vTexCoord = TexCoord;
}

// PUBLIC DOMAIN CRT STYLED SCAN-LINE SHADER
//
//   by Timothy Lottes
//
// This is more along the style of a really good CGA arcade monitor.
// With RGB inputs instead of NTSC.
// The shadow mask example has the mask rotated 90 degrees for less chromatic aberration.
//
// Left it unoptimized to show the theory behind the algorithm.
//
// It is an example what I personally would want as a display option for pixel art games.
// Please take and use, change, or whatever.

#pragma stage fragment
layout(location = 0) in vec2 vTexCoord;
layout(location = 1) in vec2 FragCoord;
layout(location = 0) out vec4 FragColor;
layout(set = 0, binding = 2) uniform sampler2D horz3minus1;
layout(set = 0, binding = 3) uniform sampler2D horz3plus1;
layout(set = 0, binding = 4) uniform sampler2D horz5minus2;
layout(set = 0, binding = 5) uniform sampler2D horz5;
layout(set = 0, binding = 6) uniform sampler2D horz5plus2;
layout(set = 0, binding = 7) uniform sampler2D horz7minus1;
layout(set = 0, binding = 8) uniform sampler2D horz7;
layout(set = 0, binding = 9) uniform sampler2D horz7plus1;

// Linear to sRGB.
// Assuming using sRGB typed textures this should not be needed.
float ToSrgb1(float c)
{
   return(c<0.0031308?c*12.92:1.055*pow(c,0.41666)-0.055);
}

vec3 ToSrgb(vec3 c)
{
   return vec3(ToSrgb1(c.r),ToSrgb1(c.g),ToSrgb1(c.b));
}
  
// Distance in emulated pixels to nearest texel.
vec2 Dist(vec2 pos){pos=pos*global.SourceSize.xy;return -((pos-floor(pos))-vec2(0.5));}
    
// 1D Gaussian.
float Gaus(float pos,float scale){return exp2(scale*pow(abs(pos),shape));}
  
// Return scanline weight.
float Scan(vec2 pos,float off){
  float dst=Dist(pos).y;
  return Gaus(dst+off,hardScan);}
  
// Return scanline weight for bloom.
float BloomScan(vec2 pos,float off){
  float dst=Dist(pos).y;
  return Gaus(dst+off,hardBloomScan);}
  
// Allow nearest three lines to effect pixel.
vec3 Tri(vec2 pos){
  vec3 a=texture(horz3minus1, pos).rgb;//Horz3(pos,-1.0);
  vec3 b=texture(horz5, pos).rgb;//Horz5(pos, 0.0);
  vec3 c=texture(horz3plus1, pos).rgb;//Horz3(pos, 1.0);
  float wa=Scan(pos,-1.0);
  float wb=Scan(pos, 0.0);
  float wc=Scan(pos, 1.0);
  return a*wa+b*wb+c*wc;}
  
// Small bloom.
vec3 Bloom(vec2 pos){
  vec3 a=texture(horz5minus2, pos).rgb;//Horz5(pos,-2.0);
  vec3 b=texture(horz7minus1, pos).rgb;//Horz7(pos,-1.0);
  vec3 c=texture(horz7, pos).rgb;//Horz7(pos, 0.0);
  vec3 d=texture(horz7plus1, pos).rgb;//Horz7(pos, 1.0);
  vec3 e=texture(horz5plus2, pos).rgb;//Horz5(pos, 2.0);
  float wa=BloomScan(pos,-2.0);
  float wb=BloomScan(pos,-1.0);
  float wc=BloomScan(pos, 0.0);
  float wd=BloomScan(pos, 1.0);
  float we=BloomScan(pos, 2.0);
  return a*wa+b*wb+c*wc+d*wd+e*we;}
  
// Distortion of scanlines, and end of screen alpha.
vec2 Warp(vec2 pos){
  pos=pos*2.0-1.0;    
  pos*=vec2(1.0+(pos.y*pos.y)*warpX,1.0+(pos.x*pos.x)*warpY);
  return pos*0.5+0.5;}
  
// Shadow mask.
vec3 Mask(vec2 pos){
  vec3 mask=vec3(maskDark,maskDark,maskDark);
  
// Very compressed TV style shadow mask.
  if (shadowMask == 1.0) {
    float line=maskLight;
    float odd=0.0;
    if(fract(pos.x/6.0)<0.5)odd=1.0;
    if(fract((pos.y+odd)/2.0)<0.5)line=maskDark;  
    pos.x=fract(pos.x/3.0);
   
    if(pos.x<0.333)mask.r=maskLight;
    else if(pos.x<0.666)mask.g=maskLight;
    else mask.b=maskLight;
    mask*=line;  
  } 

// Aperture-grille.
  else if (shadowMask == 2.0) {
    pos.x=fract(pos.x/3.0);

    if(pos.x<0.333)mask.r=maskLight;
    else if(pos.x<0.666)mask.g=maskLight;
    else mask.b=maskLight;
  } 

// Stretched VGA style shadow mask (same as prior shaders).
  else if (shadowMask == 3.0) {
    pos.x+=pos.y*3.0;
    pos.x=fract(pos.x/6.0);

    if(pos.x<0.333)mask.r=maskLight;
    else if(pos.x<0.666)mask.g=maskLight;
    else mask.b=maskLight;
  }

// VGA style shadow mask.
  else if (shadowMask == 4.0) {
    pos.xy=floor(pos.xy*vec2(1.0,0.5));
    pos.x+=pos.y*3.0;
    pos.x=fract(pos.x/6.0);

    if(pos.x<0.333)mask.r=maskLight;
    else if(pos.x<0.666)mask.g=maskLight;
    else mask.b=maskLight;
  }

  return mask;}

void main()
{
vec2 pos=Warp(vTexCoord);
vec3 outColor = Tri(pos);
  #ifdef DO_BLOOM
  //Add Bloom
  outColor.rgb+=Bloom(pos)*bloomAmount;
  #endif
if(shadowMask > 0.0)
      outColor.rgb*=Mask(vTexCoord.xy / global.OutputSize.zw * 1.000001);
//hacky clamp fix
vec2 bordertest = (pos);
if ( bordertest.x > 0.0001 && bordertest.x < 0.9999 && bordertest.y > 0.0001 && bordertest.y < 0.9999)
outColor.rgb = outColor.rgb;
else
outColor.rgb = vec3(0.0);

   FragColor = vec4(ToSrgb(outColor.rgb), 1.0);
}