jsl-prism.MaskDrawCircle.jsl Maven / Gradle / Ivy
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param float2 idim;
// See MaskFillCircle.jsl for a description of the parameters and formula
// for computing the distance to the edge of a circle. This shader simply
// performs the computation twice - once for the entering the outer edge
// of the stroked circle and again for leaving the inner edge of the stroke.
float mask(float2 tco, float2 odim)
{
// Amortize the length squared and "subtract .25" calculations
float lensq_m_25 = dot(tco, tco) - 0.25;
float ocov = clamp(0.5 * (odim.x + 1.0 - lensq_m_25 / odim.x), 0.0, odim.y);
float icov = clamp(0.5 * (idim.x + 1.0 - lensq_m_25 / idim.x), 0.0, idim.y);
return ocov - icov;
}