slang-shaders/crt/crt-lottes.slang

#version 450

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 Source;

// -- config  -- //

#define hardScan -8.0
#define hardPix -3.0
#define warpX 0.031
#define warpY 0.041
#define maskDark 0.5
#define maskLight 1.5
#define scaleInLinearGamma 1
#define shadowMask 1
#define brightboost 1
#define hardBloomScan -2.0
#define hardBloomPix -1.5
#define bloomAmount 1.0/16.0
#define shape 2.0

//Uncomment to reduce instructions with simpler linearization
//(fixes HD3000 Sandy Bridge IGP)
//#define SIMPLE_LINEAR_GAMMA
#define DO_BLOOM 1

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

// sRGB to Linear.
// Assuming using sRGB typed textures this should not be needed.
#ifdef SIMPLE_LINEAR_GAMMA
float ToLinear1(float c)
{
   return c;
}
float3 ToLinear(vec3 c)
{
   return c;
}
vec3 ToSrgb(vec3 c)
{
   return pow(c, 1.0 / 2.2);
}
#else
float ToLinear1(float c)
{
   if (scaleInLinearGamma==0) return c;
   return(c<=0.04045)?c/12.92:pow((c+0.055)/1.055,2.4);
}

vec3 ToLinear(vec3 c)
{
   if (scaleInLinearGamma==0) return c;
   return vec3(ToLinear1(c.r),ToLinear1(c.g),ToLinear1(c.b));
}

// Linear to sRGB.
// Assuming using sRGB typed textures this should not be needed.
float ToSrgb1(float c)
{
   if (scaleInLinearGamma==0) return c;
   return(c<0.0031308?c*12.92:1.055*pow(c,0.41666)-0.055);
}

vec3 ToSrgb(vec3 c)
{
   if (scaleInLinearGamma==0) return c;
   return vec3(ToSrgb1(c.r),ToSrgb1(c.g),ToSrgb1(c.b));
}
#endif



// Nearest emulated sample given floating point position and texel offset.
// Also zero's off screen.
vec3 Fetch(vec2 pos,vec2 off){
  pos=(floor(pos*global.SourceSize.xy+off)+vec2(0.5,0.5))/global.SourceSize.xy;
#ifdef SIMPLE_LINEAR_GAMMA
  return ToLinear(brightboost * pow(texture(Source,pos.xy).rgb, 2.2));
#else
  return ToLinear(brightboost * texture(Source,pos.xy).rgb);}
#endif
  
// 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));}

// 3-tap Gaussian filter along horz line.
vec3 Horz3(vec2 pos,float off){
  vec3 b=Fetch(pos,vec2(-1.0,off));
  vec3 c=Fetch(pos,vec2( 0.0,off));
  vec3 d=Fetch(pos,vec2( 1.0,off));
  float dst=Dist(pos).x;
  // Convert distance to weight.
  float scale=hardPix;
  float wb=Gaus(dst-1.0,scale);
  float wc=Gaus(dst+0.0,scale);
  float wd=Gaus(dst+1.0,scale);
  // Return filtered sample.
  return (b*wb+c*wc+d*wd)/(wb+wc+wd);}

// 5-tap Gaussian filter along horz line.
vec3 Horz5(vec2 pos,float off){
  vec3 a=Fetch(pos,vec2(-2.0,off));
  vec3 b=Fetch(pos,vec2(-1.0,off));
  vec3 c=Fetch(pos,vec2( 0.0,off));
  vec3 d=Fetch(pos,vec2( 1.0,off));
  vec3 e=Fetch(pos,vec2( 2.0,off));
  float dst=Dist(pos).x;
  // Convert distance to weight.
  float scale=hardPix;
  float wa=Gaus(dst-2.0,scale);
  float wb=Gaus(dst-1.0,scale);
  float wc=Gaus(dst+0.0,scale);
  float wd=Gaus(dst+1.0,scale);
  float we=Gaus(dst+2.0,scale);
  // Return filtered sample.
  return (a*wa+b*wb+c*wc+d*wd+e*we)/(wa+wb+wc+wd+we);}
  
// 7-tap Gaussian filter along horz line.
vec3 Horz7(vec2 pos,float off){
  vec3 a=Fetch(pos,vec2(-3.0,off));
  vec3 b=Fetch(pos,vec2(-2.0,off));
  vec3 c=Fetch(pos,vec2(-1.0,off));
  vec3 d=Fetch(pos,vec2( 0.0,off));
  vec3 e=Fetch(pos,vec2( 1.0,off));
  vec3 f=Fetch(pos,vec2( 2.0,off));
  vec3 g=Fetch(pos,vec2( 3.0,off));
  float dst=Dist(pos).x;
  // Convert distance to weight.
  float scale=hardBloomPix;
  float wa=Gaus(dst-3.0,scale);
  float wb=Gaus(dst-2.0,scale);
  float wc=Gaus(dst-1.0,scale);
  float wd=Gaus(dst+0.0,scale);
  float we=Gaus(dst+1.0,scale);
  float wf=Gaus(dst+2.0,scale);
  float wg=Gaus(dst+3.0,scale);
  // Return filtered sample.
  return (a*wa+b*wb+c*wc+d*wd+e*we+f*wf+g*wg)/(wa+wb+wc+wd+we+wf+wg);}
  
// 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=Horz3(pos,-1.0);
  vec3 b=Horz5(pos, 0.0);
  vec3 c=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=Horz5(pos,-2.0);
  vec3 b=Horz7(pos,-1.0);
  vec3 c=Horz7(pos, 0.0);
  vec3 d=Horz7(pos, 1.0);
  vec3 e=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);

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