52 lines
1.4 KiB
GLSL
52 lines
1.4 KiB
GLSL
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#version 440
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layout( location = 0 ) in vec2 coord; // [-1.0,+1.0]x[-1.0,+1.0]
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layout( location = 0 ) out vec4 fragColor;
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layout( std140, binding = 0 ) uniform buf
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{
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mat4 matrix;
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vec4 color; // shadow's color
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vec2 offset; // shadow's offset (x,y) : [-1.0, +1.0]x[-1.0,+1.0]
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float radius; // arc's radius [0.0, 1.0]
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float thickness; // arc's thickness [0.0, 1.0]
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float startAngle; // arc's start angle [rad]
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float spanAngle; // arc's span angle [rad]
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float extend; // shadow length [0.0, 1.0]
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float opacity; // overall opacity [0.0, 1.0]
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} ubuf;
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float sdRing( in vec2 p, in vec2 n, in float r, in float th )
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{
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p.x = abs(p.x);
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p = mat2(n.x,n.y,-n.y,n.x)*p;
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return max( abs(length(p)-r)-th*0.5,
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length(vec2(p.x,max(0.0,abs(r-p.y)-th*0.5)))*sign(p.x) );
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}
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void main()
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{
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// rotation
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vec2 p = coord + ubuf.offset;
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float ra = -ubuf.startAngle - ubuf.spanAngle / 2.0;
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{
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float sin_ra = sin(ra);
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float cos_ra = cos(ra);
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mat2 transform = mat2
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(
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cos_ra, -sin_ra,
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sin_ra, cos_ra
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);
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p = transform * p;
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}
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float t = abs(ubuf.spanAngle) / 2.0; // half span angle
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vec2 cs = vec2(cos(t),sin(t));
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float d = sdRing(p, cs, ubuf.radius / 2.0, ubuf.thickness);
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float a = 1.0 - smoothstep(0.0, ubuf.extend, d);
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fragColor = vec4(ubuf.color.rgb, 1.0) * a * ubuf.opacity;
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}
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