<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">I was just at this moment thinking the same thing!<div><br></div><div>Thanks! </div><div><br></div><div>I’ll check.</div><div>Rick<br><br><div id="AppleMailSignature">Sent from my iPad</div><div><br>On Dec 5, 2017, at 8:10 AM, Aron Helser <<a href="mailto:aron.helser@kitware.com">aron.helser@kitware.com</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="ltr">Auto invQ = <span style="font-size:12.8px">q.inverse();</span><div><span style="font-size:12.8px">Auto unRotPt = </span>invQ <span style="font-size:12.8px"> * rotPt * </span>invQ<span style="font-size:12.8px">.conjugate();</span></div><div><span style="font-size:12.8px"><br></span></div><div><span style="font-size:12.8px">that ought to work....</span></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Dec 4, 2017 at 11:56 PM, Richard Frank <span dir="ltr"><<a href="mailto:rickfrank@me.com" target="_blank">rickfrank@me.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div lang="EN-US" link="#0563C1" vlink="#954F72"><div class="m_-719938070757537405WordSection1"><p class="MsoNormal">Hi,<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">I can rotation a point as below, but how to simply get back the original point?<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">vnl_vector_fixed<float,3> pt = {0,1,0};<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">vnl_vector_fixed<float,3> axis = {0,0,1};<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">vnl_quaternion<float> q = vnl_quaternion<float>(axis,45 * M_PI / 180.0);<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">auto rotPt = q * pt * q.conjugate();<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">// how to invert?<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">Auto unRotPt = q.inverse() * rotPt; // doesn’t seem to work<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">Thanks<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">Rick<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal"><u></u> <u></u></p></div></div><br>______________________________<wbr>_________________<br>
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