draw2d/curve/quad_float64.go

// Copyright 2010 The draw2d Authors. All rights reserved.
// created: 17/05/2011 by Laurent Le Goff
package curve

import (
	"math"
)

//X1, Y1, X2, Y2, X3, Y3 float64
type QuadCurveFloat64 [6]float64

func (c *QuadCurveFloat64) Subdivide(c1, c2 *QuadCurveFloat64) {
	// Calculate all the mid-points of the line segments
	//----------------------
	c1[0], c1[1] = c[0], c[1]
	c2[4], c2[5] = c[4], c[5]
	c1[2] = (c[0] + c[2]) / 2
	c1[3] = (c[1] + c[3]) / 2
	c2[2] = (c[2] + c[4]) / 2
	c2[3] = (c[3] + c[5]) / 2
	c1[4] = (c1[2] + c2[2]) / 2
	c1[5] = (c1[3] + c2[3]) / 2
	c2[0], c2[1] = c1[4], c1[5]
	return
}

func (curve *QuadCurveFloat64) Segment(t LineTracer, flattening_threshold float64) {
	var curves [CurveRecursionLimit]QuadCurveFloat64
	curves[0] = *curve
	i := 0
	// current curve
	var c *QuadCurveFloat64
	var dx, dy, d float64

	for i >= 0 {
		c = &curves[i]
		dx = c[4] - c[0]
		dy = c[5] - c[1]

		d = math.Abs(((c[2]-c[4])*dy - (c[3]-c[5])*dx))

		if (d*d) < flattening_threshold*(dx*dx+dy*dy) || i == len(curves)-1 {
			t.LineTo(c[4], c[5])
			i--
		} else {
			// second half of bezier go lower onto the stack
			c.Subdivide(&curves[i+1], &curves[i])
			i++
		}
	}
}