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[SVG12Mobile] Issue with Transform Normalization example

From: Boris Zbarsky <bzbarsky@mit.edu>
Date: Tue, 24 Jan 2006 11:03:46 -0600
Message-ID: <43D65DF2.2030105@mit.edu>
To: www-svg@w3.org

Transform normalization [1] seems to allow significant loss of precision (in 
this case, square root of 2 to 3 significant digits, wheareas I suspect any 
reasonable impl would have at least 5 significant digits (that's what 16.16 
fixed-point gives you; floating point does much better for square root of 2)).

If the desire is to avoid long strings of decimals (as would appear in a 
real-life implementation of such normalization, I should note), perhaps the 
example should use a rotation angle with rational sine and cosine (say 90 
degrees).  But I would prefer the example to have something resembling expected 
output, assuming either 16.16 fixed or floating point storage, so that people 
have an idea of what such normalization does.  Possibly the example could even 
list both outputs so that it becomes very clear that such normalization makes 
the return value completely implementation-dependent.

-Boris

[1] http://www.w3.org/TR/SVGMobile12/svgudom.html#TransformNormalization
Received on Tuesday, 24 January 2006 17:03:56 GMT

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