<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Jim,<div class="">If I understand your question correctly, the student would like the chicken to spin on its own axis while moving toward the bunny, much as the same way the moon would rotate while revolving round the earth (the difference being that the chicken is not orbiting the bunny but moving toward it).</div><div class=""><br class=""></div><div class="">I am not sure that this is a bug, but it is certainly a side-effect of the implementation. I notice that if the chicken <b class="">moves to</b> the bunny, you do get the behavior I described above. <b class="">move to </b> is an absolute command as that essentially Alice is setting the center point of the object to the center point of the target, and then animating that movement. </div><div class=""><br class=""></div><div class="">The idea of <b class="">move toward</b>, was to provide a way to have one object approach another without colliding with it. Like <b class="">move</b>, iit is a relational action, using the object's orientation to determine the animation. And in this <b class="">do together</b>, as you know, that orientation is always changing creating the spinning, just as would happen with a <b class="">move</b>.</div><div class=""><br class=""></div><div class="">The solution is to use a different point of view, or orientation, to determine the path of the <b class="">move toward</b>. In the code snippet I have attached, you will see that I am using the <b class=""><i class="">as seen by</i></b> modifier to tell the <i class="">chicken</i> to <b class="">move toward</b> the <i class="">bunny</i> <b class=""><i class="">as seen by</i></b> the <i class="">ground</i>. (It turns out that I could also have said <b class=""><i class="">as seen by</i></b> the <i class="">bunny</i>).</div><div class=""><br class=""></div><div class="">I believe that this is generating the behavior your student was looking for.</div><div class=""><br class=""></div><div class="">I have to tell you, you and your students always come up with interesting questions, and I enjoy wrestling with them.</div><div class=""><br class=""></div><div class="">Let me know if I misunderstood or if there are any other questions…</div><div class=""><br class=""></div><div class=""><img apple-inline="yes" id="4DCDE1E4-3CF6-4A1E-A738-872472E70E22" src="cid:B6E847AE-0C72-4970-97A7-5C2B2C2C31DC@fios-router.home" class=""></div><div class=""><br class=""></div><div class="">All the best,</div><div class="">Don Slater</div><div class=""><div class=""><br class="">Alice Project<br class="">Carnegie Mellon University<br class="">Entertainment Technology Center<br class="">700 Technology Drive<br class="">Pittsburgh, PA 15219<br class=""><br class="">Email: <a href="mailto:dslater@cmu.edu" class="">dslater@cmu.edu</a><br class=""><br class="">I have learned this at least by my experiment: that if one advances confidently in the direction of his dreams, and endeavors to live the life he has imagined, he will meet with a success unexpected in common hours.<br class="">--- Henry David Thoreau<br class=""><br class="">The true object of all human life is play. -- G.K. Chesterton<br class=""><br class="">
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<br class=""><div><blockquote type="cite" class=""><div class="">On Feb 9, 2017, at 4:22 PM, Vanderhyde, James via alice-teachers <<a href="mailto:alice-teachers@lists.andrew.cmu.edu" class="">alice-teachers@lists.andrew.cmu.edu</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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I am using Alice 2.4.3. One of my students today produced unexpected behavior using “move toward.” Consider this code:
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<table cellpadding="2" cellspacing="0" width="100%" style="font-family: -webkit-standard;" class="">
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<td colspan="2" bgcolor="#f2e6ff" style="border-left-width: 1px; border-left-style: solid; border-left-color: rgb(192, 192, 192); border-top-width: 1px; border-top-style: solid; border-top-color: rgb(192, 192, 192); border-right-width: 1px; border-right-style: solid; border-right-color: rgb(192, 192, 192);" class="">
<b class="">Do together</b></td>
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<td width="20" rowspan="2" bgcolor="#f2e6ff" style="border-left-width: 1px; border-left-style: solid; border-left-color: rgb(192, 192, 192); border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: rgb(192, 192, 192);" class="">
</td>
<td width="100%" colspan="1" bgcolor="#fff7e6" style="border: 1px solid rgb(192, 192, 192);" class="">
<span style="background-color: rgb(240, 240, 255);" class=""><b class="">chicken</b></span> <b class="">turn </b><span style="background-color: rgb(240, 240, 255);" class=""><b class="">left</b></span> <span style="background-color: rgb(240, 240, 255);" class=""><b class="">1 </b>revolution</span></td>
</tr>
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<td width="100%" colspan="1" bgcolor="#fff7e6" style="border: 1px solid rgb(192, 192, 192);" class="">
<span style="background-color: rgb(240, 240, 255);" class=""><b class="">chicken</b></span> <b class="">move </b><span style="background-color: rgb(240, 240, 255);" class="">amount = <b class="">2 </b>meters</span> <b class="">toward </b><span style="background-color: rgb(240, 240, 255);" class="">target
= <b class="">bunny</b></span></td>
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<div class="">The chicken turns in a circle rather than turning while moving toward the bunny. I know that “move forward” combined with “turn left” will result in circular movement. But I don’t understand why “move toward” is doing it. After all, “move toward”
by itself works no matter which way the chicken is facing.</div>
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<div class="">Is this a bug or desired behavior? If desired, can someone explain it to me?</div>
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<div class="">James<br class="">
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—<br class="">
James Vanderhyde<br class="">
Assistant Professor, Computer Science<br class="">
Program Director, Master of Applied Computer Science<br class="">
Saint Xavier University<br class="">
3700 W. 103rd St.<br class="">
Chicago, IL 60655<br class="">
773-298-3454</div>
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