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in vec3 vCoord;
in vec2 tCoord;
out vec2 sampleCoord;
out vec2 alphas;
uniform mat4 mvp;
uniform mat4 modelView;
uniform int textureWidth;
uniform int textureHeight;
uniform float fontScale;
float thresholdFunc(float scale)
{
float base = 0.5;
float baseDev = 0.065;
float devScaleMin = 0.15;
float devScaleMax = 0.3;
return base - ((clamp(scale, devScaleMin, devScaleMax) - devScaleMin)
/ (devScaleMax - devScaleMin) * -baseDev + baseDev);
}
float spreadFunc(float scale)
{
return 0.06 / scale;
}
vec2 alphaRange(float scale)
{
float base = thresholdFunc(scale);
float range = spreadFunc(scale);
float alphaMin = max(0.0, base - range);
float alphaMax = min(base + range, 1.0);
return vec2(alphaMin, alphaMax);
}
void main()
{
float scale = fontScale * sqrt(abs(determinant(modelView)));
alphas = alphaRange(scale);
sampleCoord = tCoord * vec2(1.0 / float(textureWidth), 1.0 / float(textureHeight));
gl_Position = mvp * vec4(vCoord, 1.0);
}
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