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Skateboard Tricks and Topological Flips

113 点作者 user2994cb将近 4 年前

10 条评论

fokinsean超过 3 年前
Here&#x27;s a fun one to debate with your skate friends, nollie and fakie tricks are &quot;swapped&quot;.<p>For example:<p>- nollie fs 180 and fakie fs 180 (fs half cab) are two different directions: nollie fs 180 is in front of you and fakie fs 180 is behind you going blind<p>- nollie 5-0 and fakie 5-0 (fakie switch nosegrind) lean differently on the grind: nollie 5-0 you pop off your nose and land on your back truck, fakie 5-0 you pop off your tail and land on your front truck<p>- nollie noseslide and fakie noseslide are different motions to get into the slide: nollie nose you pop off nose and land on the nose in the ledge, fakie nose you pop off tail and land on the nose but you do a sort of half cab<p>The key distinction in the argument is that in fakie, your tail is always considered your &quot;tail&quot;. Therefore you treat any derived tricks as being &quot;backwards&quot;. In the 5-0 and noseslide examples, you&#x27;re still popping off the front of your board, but you classify it as nose or tail based on if it&#x27;s nollie or fakie.<p>There are caveats though such as &quot;fakie crook&quot; where if you kept the rule it should be &quot;fakie suski&quot;, which no one says.<p>There&#x27;s a million arbitrary and nonsensical rules in skateboarding which is part of the reason to love it, especially for something that &quot;has no rules&quot;.<p>And remember, never carry your board by your truck :)
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nathancahill超过 3 年前
Generated the animations from the repo linked in the paper: <a href="https:&#x2F;&#x2F;imgur.com&#x2F;a&#x2F;SJcAvHF" rel="nofollow">https:&#x2F;&#x2F;imgur.com&#x2F;a&#x2F;SJcAvHF</a><p>The specific tricks with their matrices are here: <a href="https:&#x2F;&#x2F;github.com&#x2F;holomorpheus&#x2F;topological-flips&#x2F;blob&#x2F;main&#x2F;matrixTricks.py#L52" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;holomorpheus&#x2F;topological-flips&#x2F;blob&#x2F;main&#x2F;...</a>
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mrspeaker超过 3 年前
Reminds me of this (less math-heavy!) analysis of &quot;Skateboarding Science&quot; about Rodney Mullen: <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=yFRPhi0jhGc" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=yFRPhi0jhGc</a>
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fokinsean超过 3 年前
I was hoping they would come up with a mathematical way to distinguish an impossible from a 360 shuv :)
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RhysU超过 3 年前
The end of the paper points to <a href="https:&#x2F;&#x2F;github.com&#x2F;holomorpheus&#x2F;topological-flips" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;holomorpheus&#x2F;topological-flips</a>
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rawling超过 3 年前
&gt; As a last example we will describe the hardflip. This is a simultaneous half kickflip (a 180 degree rotation about the axis joining the tail to the nose of the skateboard) and a 180 degree rotation about the x-axis in the right-hand orientation.<p>Is it? Isn&#x27;t a hardflip just a mirror of the varial kickflip they describe, and rotation around their x-axis something else entirely?
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nerdponx超过 3 年前
I really like the phrase &quot;quaternionic varial kickflip&quot;.
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joncrane超过 3 年前
Correct me if I&#x27;m wrong, but the whole beginning of the article implies that the skateboarder is &quot;regular&quot; in terms of foot placement, meaning the right foot is on the tail and the left foot is at the front.<p>The fact that each skater can reverse their stance (aka switchstance), doesn&#x27;t that double the possible number of flip tricks?
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kevinventullo超过 3 年前
So if I understand correctly, letting “~” denote homotopy equivalence,<p><pre><code> Kickflip ~ 360 shove it Ollie ~ 720 shove it ~ double kickflip </code></pre> I may have missed it in the paper, but does anyone have intuition about how to visualize these homotopies? I don’t get how to continuously deform a 720 shove it into an Ollie.
joncrane超过 3 年前
So what are the 4 tricks?<p>Kickflip, heelflip, flip + shove it in the &quot;natural direction&quot; (e.g. varial kickflip, 360 kickflip), and flip + shove it in the unnatural direction (e.g. hard flip)?
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