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// ----------------------------------------------------------------------------
// Copyright (c) 2014, Nicolas P. Rougier. All Rights Reserved.
// Distributed under the (new) BSD License.
// ----------------------------------------------------------------------------
/* ---------------------------------------------------------
Compute antialiased fragment color for an outlined shape.
Parameters:
-----------
distance : signed distance to border (in pixels)
linewidth: Stroke line width (in pixels)
antialias: Stroke antialiased area (in pixels)
stroke: Stroke color
fill: Fill color
Return:
-------
Fragment color (vec4)
--------------------------------------------------------- */
vec4 outline(float distance, float linewidth, float antialias, vec4 fg_color, vec4 bg_color)
{
vec4 frag_color;
float t = linewidth/2.0 - antialias;
float signed_distance = distance;
float border_distance = abs(signed_distance) - t;
float alpha = border_distance/antialias;
alpha = exp(-alpha*alpha);
if( border_distance < 0.0 )
frag_color = fg_color;
else if( signed_distance < 0.0 )
frag_color = mix(bg_color, fg_color, sqrt(alpha));
else
frag_color = vec4(fg_color.rgb, fg_color.a * alpha);
return frag_color;
}
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