73 lines
1.7 KiB
GLSL
73 lines
1.7 KiB
GLSL
/*
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Heavily inspired by code from the kirigami project:
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Copyright 2020 Arjen Hiemstra <ahiemstra@heimr.nl>
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License: LGPL-2.0-or-later
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https://iquilezles.org/www/articles/distfunctions2d/distfunctions2d.htm
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Copyright: 2017 Inigo Quilez
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License: MIT
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*/
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uniform lowp float opacity;
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uniform lowp float extent;
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uniform lowp vec4 radius;
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uniform lowp vec4 color;
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uniform lowp vec2 offset;
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uniform lowp vec2 aspect;
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varying lowp vec2 coord;
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lowp float effectiveRadius( in lowp vec4 radii, in lowp vec2 point )
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{
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if ( point.x > 0.0 )
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return ( point.y > 0.0) ? radii.x : radii.y;
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else
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return ( point.y > 0.0) ? radii.z : radii.w;
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}
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bool isInside( in lowp vec2 point, in lowp vec2 size, in lowp vec4 radii )
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{
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lowp float r = effectiveRadius( radii, point );
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lowp vec2 d = abs(point) - size + r;
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lowp float l = min( max(d.x, d.y), 0.0) + length( max(d, 0.0) ) - r;
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return l <= 0.0;
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}
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lowp float shadowAt(
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in lowp vec2 point, in lowp vec2 size, in lowp vec4 radii )
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{
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lowp float r = effectiveRadius( radii, point );
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lowp vec2 d = abs(point) - size + r;
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return min( max(d.x, d.y), 0.0) + length( max(d, 0.0) ) - r;
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}
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void main()
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{
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lowp vec4 col = vec4(0.0);
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if ( extent > 0.0 && opacity > 0.0 )
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{
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lowp float t = 1.0 + 2.0 * length( offset ) + extent;
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if ( !isInside( coord, aspect / t, radius / t) )
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{
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const lowp float minRadius = 0.05;
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lowp float e2 = 0.5 * extent;
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lowp vec4 f = minRadius / max( radius, minRadius );
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lowp vec4 r = radius + e2 * f;
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lowp float shadow = shadowAt(
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coord - 2.0 * offset / t, aspect / t, r / t);
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lowp float v = smoothstep( -e2, e2, shadow );
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col = mix( color, vec4(0.0), v ) * opacity;
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}
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}
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gl_FragColor = col;
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}
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