maplibre-gl/src/shaders/fill_outline_pattern.fragment.glsl

uniform vec2 u_texsize;
uniform sampler2D u_image;
uniform float u_fade;

varying vec2 v_pos_a;
varying vec2 v_pos_b;
varying vec2 v_pos;

#pragma mapbox: define lowp float opacity
#pragma mapbox: define lowp vec4 pattern_from
#pragma mapbox: define lowp vec4 pattern_to

void main() {
    #pragma mapbox: initialize lowp float opacity
    #pragma mapbox: initialize mediump vec4 pattern_from
    #pragma mapbox: initialize mediump vec4 pattern_to

    vec2 pattern_tl_a = pattern_from.xy;
    vec2 pattern_br_a = pattern_from.zw;
    vec2 pattern_tl_b = pattern_to.xy;
    vec2 pattern_br_b = pattern_to.zw;

    vec2 imagecoord = mod(v_pos_a, 1.0);
    vec2 pos = mix(pattern_tl_a / u_texsize, pattern_br_a / u_texsize, imagecoord);
    vec4 color1 = texture2D(u_image, pos);

    vec2 imagecoord_b = mod(v_pos_b, 1.0);
    vec2 pos2 = mix(pattern_tl_b / u_texsize, pattern_br_b / u_texsize, imagecoord_b);
    vec4 color2 = texture2D(u_image, pos2);

    // find distance to outline for alpha interpolation

    float dist = length(v_pos - gl_FragCoord.xy);
    float alpha = 1.0 - smoothstep(0.0, 1.0, dist);


    gl_FragColor = mix(color1, color2, u_fade) * alpha * opacity;

#ifdef OVERDRAW_INSPECTOR
    gl_FragColor = vec4(1.0);
#endif
}