33 lines
687 B
GLSL
33 lines
687 B
GLSL
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#version 440
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layout( location = 0 ) in vec2 coord;
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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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vec2 centerCoord;
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float start;
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float span;
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float opacity;
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} ubuf;
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layout( binding = 1 ) uniform sampler2D palette;
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vec4 colorAt( highp float value )
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{
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return texture( palette, vec2( value, 0.0 ) );
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}
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void main()
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{
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/*
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angles as ratio of a rotation:
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start: [ 0.0, 1.0 [
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span: ] -1.0, 1.0 [
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*/
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float v = sign( ubuf.span ) * ( atan( -coord.y, coord.x ) / 6.2831853 - ubuf.start );
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fragColor = colorAt( ( v - floor( v ) ) / abs( ubuf.span ) ) * ubuf.opacity;
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}
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