37 lines
1.3 KiB
GLSL
37 lines
1.3 KiB
GLSL
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#define M_1_SQRTPI 0.5641895835477563 /* 1/sqrt(pi) */
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/**
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* We want to know how much a pixel is covered by a line.
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* We replace the square pixel with acircle of the same area and try to find the intersection area.
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* The area we search is the circular segment. https://en.wikipedia.org/wiki/Circular_segment
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* The formula for the area uses inverse trig function and is quite complexe. Instead,
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* we approximate it by using the smoothstep function and a 1.05 factor to the disc radius.
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*/
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#define DISC_RADIUS (M_1_SQRTPI * 1.05)
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#define GRID_LINE_SMOOTH_START (0.5 - DISC_RADIUS)
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#define GRID_LINE_SMOOTH_END (0.5 + DISC_RADIUS)
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flat in vec4 finalColorOuter_f;
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in vec4 finalColor_f;
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noperspective in float edgeCoord_f;
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out vec4 FragColor;
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void main()
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{
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float dist = abs(edgeCoord_f) - max(sizeEdge - 0.5, 0.0);
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float dist_outer = dist - max(sizeEdge, 1.0);
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#ifdef USE_SMOOTH_WIRE
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float mix_w = smoothstep(GRID_LINE_SMOOTH_START, GRID_LINE_SMOOTH_END, dist);
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float mix_w_outer = smoothstep(GRID_LINE_SMOOTH_START, GRID_LINE_SMOOTH_END, dist_outer);
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#else
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float mix_w = step(0.5, dist);
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float mix_w_outer = step(0.5, dist_outer);
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#endif
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/* Line color & alpha. */
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FragColor = mix(finalColorOuter_f, finalColor_f, 1.0 - mix_w * finalColorOuter_f.a);
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/* Line edges shape. */
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FragColor.a *= 1.0 - (finalColorOuter_f.a > 0.0 ? mix_w_outer : mix_w);
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}
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