slang-shaders/crt/shaders/glow/threshold.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;
}

#pragma stage fragment
layout(location = 0) in  vec2  vTexCoord;
layout(location = 0) out vec4  FragColor;
layout(set = 0, binding = 2) uniform sampler2D Source;

#define GLOW_WHITEPOINT 1.0
#define GLOW_ROLLOFF 3.0

void main() 
{
    vec3 color  = 1.15 * texture(Source, vTexCoord).rgb;
    vec3 factor = clamp(color / GLOW_WHITEPOINT, 0.0, 1.0);
    
    FragColor = vec4(pow(factor, vec3(GLOW_ROLLOFF)), 1.0);
}