dot-computeCurvedMidpoint: Compute point along a curved segment (quadratic Bézier)

In ggpedigree: Visualizing Pedigrees with 'ggplot2' and 'plotly'

Compute point along a curved segment (quadratic Bézier)

Description

Computes the x–y coordinates of a point along a curved segment connecting (x0, y0) to (x1, y1) using a quadratic Bézier construction. The control point is defined by an orthogonal offset from the straight-line midpoint, scaled by curvature * len and rotated by angle + shift (degrees). Vectorized over input coordinates and t.

Usage

.computeCurvedMidpoint(x0, y0, x1, y1, curvature, angle, shift = 0, t = 0.5)

computeCurvedMidpoint(x0, y0, x1, y1, curvature, angle, shift = 0, t = 0.5)

Arguments

x0	Numeric vector. X-coordinates of start points.
y0	Numeric vector. Y-coordinates of start points.
x1	Numeric vector. X-coordinates of end points.
y1	Numeric vector. Y-coordinates of end points.
curvature	Curvature scale factor (as in *geom_curve*-style helpers): the control point is placed at a distance 'curvature * len' from the segment midpoint in the rotated-perpendicular direction. Changing the sign flips the bend to the opposite side (after rotation).
angle	Scalar numeric. Base rotation in degrees applied to the perpendicular before offsetting.
shift	Scalar numeric. Additional rotation in degrees (default 0). Effective rotation is angle + shift.
t	Numeric scalar or vector in [0, 1]. Bézier parameter where 0 is the start point, 1 is the end point; default 0.5.

Details

* The unit perpendicular is constructed from the segment direction '(dx, dy)' as '(-uy, ux)' where '(ux, uy) = (dx, dy) / len'. * If an input pair yields 'len = 0' (identical endpoints), the unit direction is undefined and the resulting coordinates will be 'NA' due to division by zero; inputs should avoid zero-length segments. * Inputs of unequal length are recycled by base R. Prefer supplying conformable vectors to avoid unintended recycling.

Value

A data frame with columns x, y, and t representing the coordinates along the curved segment.

See Also

Related drawing helpers such as 'ggplot2::geom_curve()' for visual reference on curvature semantics.

ggpedigree documentation built on Sept. 13, 2025, 1:08 a.m.