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@kolen
Created July 30, 2019 21:53
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Simple dithering shader for godot engine
// Based on http://devlog-martinsh.blogspot.com/2011/03/glsl-dithering.html
shader_type canvas_item;
uniform float scale = 1.0;
float find_closest(int x, int y, float c0)
{
mat4 dither = mat4(vec4( 1.0, 33.0, 9.0, 41.0),
vec4(49.0, 17.0, 57.0, 25.0),
vec4(13.0, 45.0, 5.0, 37.0),
vec4(61.0, 29.0, 53.0, 21.0));
float limit = 0.0;
vec4 subd;
// No indexing on variables in Godot (as of 3.1)
if (x == 0) {
subd = dither[0];
} else if (x == 1) {
subd = dither[1];
} else if (x == 2) {
subd = dither[2];
} else if (x == 3) {
subd = dither[3];
}
if (y == 0) {
limit = subd[0];
} else if (y == 1) {
limit = subd[1];
} else if (y == 2) {
limit = subd[2];
} else if (y == 3) {
limit = subd[3];
}
limit = limit / 64.0;
if (c0 < limit){
return 0.0;
} else {
return 1.0;
}
}
void fragment() {
vec2 texCoord = SCREEN_UV;
vec4 lum = vec4(0.299, 0.587, 0.114, 0.0);
float grayscale = dot(texture(TEXTURE, texCoord), lum);
vec3 rgb = texture(TEXTURE, texCoord).rgb;
vec2 xy = FRAGCOORD.xy;
int x = int(mod(xy.x, 4.0));
int y = int(mod(xy.y, 4.0));
COLOR.r = find_closest(x, y, rgb.r);
COLOR.g = find_closest(x, y, rgb.g);
COLOR.b = find_closest(x, y, rgb.b);
}
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