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- // Scanline shader
- // timothylottes.blogspot.com/2014/08/scanlines.html
- // https://www.shadertoy.com/view/XsjSzR#
- //
- // 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.
- =============================================
- <vertex>
- attribute vec2 a_vertex_coordinate;
- attribute vec2 a_texture_coordinate;
- varying vec2 v_texture_coordinate;
- varying vec2 v_screen_coordinate;
- void main() {
- gl_Position = vec4(a_vertex_coordinate.xy, 0.0, 1.0);
- v_texture_coordinate = a_texture_coordinate;
- v_screen_coordinate = a_texture_coordinate * u_target_size;
- }
- </vertex>
- <fragment>
- // Optimize for resize.
- vec2 res;
- // Hardness of scanline.
- // -8.0 = soft
- // -16.0 = medium
- float hardScan=-8.0;
- // Hardness of pixels in scanline.
- // -2.0 = soft
- // -4.0 = hard
- float hardPix=-3.0;
- // Display warp.
- // 0.0 = none
- // 1.0/8.0 = extreme
- //vec2 warp=vec2(1.0/32.0,1.0/24.0);
- vec2 warp=vec2(0.0,0.0);
- // Amount of shadow mask.
- float maskDark=0.5;
- float maskLight=1.5;
- //------------------------------------------------------------------------
- // sRGB to Linear.
- // Assuing using sRGB typed textures this should not be needed.
- float ToLinear1(float c){return(c<=0.04045)?c/12.92:pow((c+0.055)/1.055,2.4);}
- vec3 ToLinear(vec3 c){return vec3(ToLinear1(c.r),ToLinear1(c.g),ToLinear1(c.b));}
- // Linear to sRGB.
- // Assuing 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));}
- // Nearest emulated sample given floating point position and texel offset.
- // Also zero's off screen.
- vec3 Fetch(sampler2D tex,vec2 pos,vec2 off){
- pos=floor(pos*res+off)/res;
- if(max(abs(pos.x-0.5),abs(pos.y-0.5))>0.5)return vec3(0.0,0.0,0.0);
- return ToLinear(texture2D(tex,pos.xy,-16.0).rgb);}
- // Distance in emulated pixels to nearest texel.
- vec2 Dist(vec2 pos){pos=pos*res;return -((pos-floor(pos))-vec2(0.5));}
- // 1D Gaussian.
- float Gaus(float pos,float scale){return exp2(scale*pos*pos);}
- // 3-tap Gaussian filter along horz line.
- vec3 Horz3(sampler2D tex,vec2 pos,float off){
- vec3 b=Fetch(tex,pos,vec2(-1.0,off));
- vec3 c=Fetch(tex,pos,vec2( 0.0,off));
- vec3 d=Fetch(tex,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(sampler2D tex,vec2 pos,float off){
- vec3 a=Fetch(tex,pos,vec2(-2.0,off));
- vec3 b=Fetch(tex,pos,vec2(-1.0,off));
- vec3 c=Fetch(tex,pos,vec2( 0.0,off));
- vec3 d=Fetch(tex,pos,vec2( 1.0,off));
- vec3 e=Fetch(tex,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);}
- // Return scanline weight.
- float Scan(vec2 pos,float off){
- float dst=Dist(pos).y;
- return Gaus(dst+off,hardScan);}
- // Allow nearest three lines to effect pixel.
- vec3 Tri(sampler2D tex,vec2 pos){
- vec3 a=Horz3(tex,pos,-1.0);
- vec3 b=Horz5(tex,pos, 0.0);
- vec3 c=Horz3(tex,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;}
- // 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)*warp.x,1.0+(pos.x*pos.x)*warp.y);
- return pos*0.5+0.5;}
- // Shadow mask.
- vec3 Mask(vec2 pos){
- pos.x+=pos.y*3.0;
- vec3 mask=vec3(maskDark,maskDark,maskDark);
- 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;}
- // Entry.
- varying vec2 v_texture_coordinate;
- varying vec2 v_screen_coordinate;
- uniform sampler2D u_texture;
- void main(){
- vec4 color = vec4(0.0, 0.0, 0.0, 1.0);
- res=u_target_size.xy;
- vec2 pos=Warp(v_screen_coordinate.xy/res);
- // hardScan=-12.0;
- // maskDark=maskLight=1.0;
- // pos=Warp(v_screen_coordinate.xy/res);
- color.rgb=Tri(u_texture,pos)*Mask(v_screen_coordinate.xy);
- color.rgb=ToSrgb(color.rgb);
- gl_FragColor = color;
- }
- </fragment>
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