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List:       openjdk-2d-dev
Subject:    [OpenJDK 2D-Dev] ArcIterator#btan(double)
From:       Ralph Hummeling <engineering () hummeling ! com>
Date:       2018-07-20 14:55:20
Message-ID: 5c6de6b53bb233009fa9216a445abcc3 () hummeling ! com
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Dear Java 2D dev team,

I came across your java.awt.geom.ArcIterator class in which an arc 
Bezier control point segment length is determined in method 
btan(double). You arrive at the following equation:
4/3*(1 - cos(a/2))/(sin(a/2))

It is mentioned that this can return NaN for small "a" and so it is 
written as:
4/3*(sin(a/2))/(1 + cos(a/2))

Please note that this relation can also be written as follows:
4/3*tan(a/4)

A performance increase and no NaN issues ;-)


Kind regards,

Ralph Hummeling
+316 5758 1679
Hummeling Engineering BV
www.hummeling.com
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