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smaller imdraw optimizations 

For polyline, don't compute each normal twice; when we're going through a line,
the "next" normal for segment N is always the "previous" normal for segment
N+1, and we can compute fewer of them.
This commit is contained in:
Seebs 2017-06-05 19:46:16 -05:00
parent 9d1fc5bd1f
commit b6533006e7
1 changed files with 4 additions and 1 deletions
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5
imdraw/imdraw.go
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@ -543,6 +543,8 @@ func (imd *IMDraw) polyline(thickness float64, closed bool) {
imd.pushPt(points[j].pos.Sub(normal), points[j])
// middle points
// compute "previous" normal:
ijNormal := points[1].pos.Sub(points[0].pos).Rotated(math.Pi / 2).Unit().Scaled(thickness / 2)
for i := 0; i < len(points); i++ {
j, k := i+1, i+2
@ -558,7 +560,6 @@ func (imd *IMDraw) polyline(thickness float64, closed bool) {
k %= len(points)
}
ijNormal := points[j].pos.Sub(points[i].pos).Rotated(math.Pi / 2).Unit().Scaled(thickness / 2)
jkNormal := points[k].pos.Sub(points[j].pos).Rotated(math.Pi / 2).Unit().Scaled(thickness / 2)
orientation := 1.0
@ -589,6 +590,8 @@ func (imd *IMDraw) polyline(thickness float64, closed bool) {
imd.pushPt(points[j].pos.Add(jkNormal), points[j])
imd.pushPt(points[j].pos.Sub(jkNormal), points[j])
}
// "next" normal becomes previous normal
ijNormal = jkNormal
}
// last point