Method quadToRel

src/main/java/field/graphics/FLine.java:315–321

draws a curve from the current position, towards (but not through) the relative position `q1x, q1y`, then onto + `x, y`.

(double q1x, double q1y, double x, double y)

		return quadTo(at.x + q1x, at.y + q1y, at.x + x, at.y + y);
	}

	/**
	 * draws a curve from the current position, towards (but not through) `q1x, q1y, q1z`, then onto `x, y`.
	 */
	public FLine quadTo(double q1x, double q1y, double q1z, double x, double y, double z) {
		if (nodes.size() == 0) return moveTo(x, y);

		Vec3 at = last().to;

		double c1x = (at.x + q1x * 2) / 3;