jsl-prism.MaskFillRoundRect.jsl Maven / Gradle / Ivy
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// oflatdim.x is the width of the non-round center portion of the round rect
// oflatdim.y is the height of the non-round center portion of the round rect
// oinvarcradii.x is the inverse of the xradius of the corner ellipse
// oinvarcradii.y is the inverse of the yradius of the corner ellipse
// total round rect dimensions are (oflatdim+oarcdim)
param float2 oinvarcradii;
float mask(float2 tco, float2 oflatdim)
{
// Create an adjusted vector to represent the location of this point
// relative to a distorted ellipse representing the rounded corners
// of the roundrect in the eccentric coordinates of that ellipse as
// defined in MaskFillEllipse.jsl.
// Points in the non-rounded interior of the round rect will be
// mapped onto the axes (or center) of the resulting ellipse.
// This all happens in a 5 step equation.
// 1 - collapse the quadrants into the non-negative one using abs()
// 2 - subtract the extents of the flat part of the round rect
// 3 - collapse negative numbers onto 0.0 using max(..., 0.0)
// 4 - convert to the eccentric coordinates by multiplying by 1/arcradii.
float2 absecctco = max(abs(tco) - oflatdim, 0.001) * oinvarcradii;
// p is now normalized to an ellipse-relative eccentric coordinate vector
// Now apply the equations from FillEllipse.jsl
float ecclensq = dot(absecctco, absecctco);
float pix = dot(absecctco / ecclensq, oinvarcradii);
return clamp(0.5 + (1.0 + 0.25*pix*pix - ecclensq)/(2.0*pix), 0.0, 1.0);
}