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precision mediump float;
uniform sampler2D u_texture;
uniform sampler2D u_jfa_outside;
uniform vec2 u_resolution;
uniform float u_feather_half;
varying vec2 v_texCoord;
vec2 decodeSeed(vec4 encoded) {
float x = floor(encoded.r * 255.0 + 0.5) * 256.0 + floor(encoded.g * 255.0 + 0.5);
float y = floor(encoded.b * 255.0 + 0.5) * 256.0 + floor(encoded.a * 255.0 + 0.5);
return vec2(x, y);
}
bool isNoSeed(vec4 encoded) {
return encoded.r > 0.99 && encoded.g > 0.99 && encoded.b > 0.99 && encoded.a > 0.99;
}
void main() {
vec2 pixelCoord = floor(v_texCoord * u_resolution);
vec4 insideEncoded = texture2D(u_texture, v_texCoord);
vec4 outsideEncoded = texture2D(u_jfa_outside, v_texCoord);
bool hasInside = !isNoSeed(insideEncoded);
bool hasOutside = !isNoSeed(outsideEncoded);
float distToInside = hasInside ? distance(pixelCoord, decodeSeed(insideEncoded)) : 1e5;
float distToOutside = hasOutside ? distance(pixelCoord, decodeSeed(outsideEncoded)) : 1e5;
float signedDist = distToOutside - distToInside;
float alpha = smoothstep(-u_feather_half, u_feather_half, signedDist);
gl_FragColor = vec4(alpha, alpha, alpha, alpha);
}
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