Find intersection point between a line and axis-aligned rectangle

Computes the intersection point(s) between a line segment (defined by two endpoints) and an axis-aligned rectangle. Returns the intersection point closest to the starting point of the line.

Usage

line_rect_intersection(x0, y0, x1, y1, half_w, half_h, gap = 0)

Arguments

x0

Numeric. X-coordinate of the line's starting point.

y0

Numeric. Y-coordinate of the line's starting point.

x1

Numeric. X-coordinate of the line's ending point.

y1

Numeric. Y-coordinate of the line's ending point.

half_w

Numeric. Half-width of the rectangle (distance from center to left/right edge).

half_h

Numeric. Half-height of the rectangle (distance from center to top/bottom edge).

gap

Controls the gap between the line and target / source box. Positive values increases the line lenght, while negative shorten the line lenght. Zero does nothing (leaves the line as-is). Default = 0.

Value

A numeric vector of length 2 with names "x" and "y", containing the coordinates of the intersection point closest to the line's start point (x0, y0). If no valid intersection is found (rare edge case), returns the rectangle center (x1, y1).

Details

The rectangle is specified by its center coordinates and half-width and half-height dimensions. The algorithm checks intersections with all four sides of the rectangle and dplyr::selects the point nearest to the line's origin.

This function is commonly used in visualization tasks such as drawing arrows or connecting lines between nodes that terminate at the boundary of node bounding boxes rather than their centers.