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Add relative move and rotate to rel plugin (#794)

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The relative position in rel plugin is currently based on the world coordinate. So for the same effect, like fly in from the right-hand side, we must use different `data-rel-x/y/z` value. Why not let the plugin do the hard part?

So I introduce a `data-rel-position`, when set to `relative`, all relative attribute is based on the position and rotation of previous slide. So no matter the rotation of previous slide, data-rel-x="1000" always looks like fly in from the right-hand side. We can change the position and rotation of one slide, and the position of all following slides will be changed too.

When `data-rel-position` is set to `relative`, relative rotation has a clear meaning. It describes the relative rotations between slides. We don't need to set rotations for all slide, setting the key slides is enough. If `data-rel-position` is not relative, the effect of `data-rel-rotate-x/y/z` is not clear, so they're only used when `data-rel-position="relative"`.

After the introduction of relative rotation, there're 6 attribute that will inherit from previous slide. If we want to set a relative X move, we have to set all other 5 attributes to 0. It's boring. So a `data-rel-clear` is used to set all 6 attributes to 0, and then the value specified in current slide is applied. 

The `examples/3D-positions/index.html` shows some usage. As you can see, the html code of two slide ring is the same, and slides except for the first two in a ring has no position attributes. It work by inheriting the previous one.

This PR invokes a lot math calculations. Basically, the rotation of a slide is translated into the coordinate describing the directions of X/Y/Z axes. And `data-rel-x/y/z` can be easily calculated by that. The rotations is the hard part, I mainly use the algorithm in the Quaternions and spatial rotation - Wikipedia to compose two and more rotations.  I'm not a math guy, hope I don't make much mistakes.
This commit is contained in:
thawk
2022-04-25 02:37:50 +08:00
committed by GitHub
parent d3760dfa0a
commit 629f7686f3
18 changed files with 10537 additions and 101 deletions
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test/plugins/rel/rotation_tests_presentation.html Normal file
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>The presentation steps used in an iframe in rel/rotation_tests.js</title>
<style type="text/css" media="screen">
.step {
position: relative;
width: 1000px;
height: 1000px;
padding: 40px 60px;
margin: 20px auto;
box-sizing: border-box;
line-height: 1.5;
background-color: white;
border-radius: 10px;
box-shadow: 0 2px 6px rgba(0, 0, 0, .1);
text-shadow: 0 2px 2px rgba(0, 0, 0, .1);
font-family: 'Open Sans', Arial, sans-serif;
font-size: 40pt;
letter-spacing: -1px;
border: solid 1px red;
}
</style>
</head>
<body class="impress-not-supported">
<div id="impress">
<div id="overview" class="step overview" data-x="0" data-y="-1000" data-z="100" data-scale="4" data-rotate-x="45">
<h1>3D Rotations Demo</h1>
</div>
<div id="step-1" class="step" data-x="0" data-y="0" data-z="0" data-goto-prev="step-8">
<p>Slide one</p>
</div>
<div id="step-2" class="step" data-rel-position="relative" data-rel-rotate-y="45" data-rel-z="-354" data-rel-x="854" data-rel-y="-125">
<p>Slide two</p>
</div>
<div id="step-3" class="step">
<p>Slide three</p>
</div>
<div id="step-4" class="step">
<p>Slide four</p>
</div>
<div id="step-5" class="step">
<p>Slide five</p>
</div>
<div id="step-6" class="step" data-rel-y="125">
<p>Slide six</p>
</div>
<div id="step-7" class="step">
<p>Slide seven</p>
</div>
<div id="step-8" class="step" data-goto-next="step-1">
<p>Slide eight</p>
</div>
<div id="reset" class="step" data-x=0 data-y=0 data-z=0 data-rotate-x=0 data-rotate-y=0 data-rotate-z=0 data-rotate-order="zyx">
<p>Reset all properties</p>
</div>
<div id="rotate" class="step" data-rotate=123>
<p>Testing the data-rotate attribute</p>
</div>
</div>
<script src="../../../js/impress.js"></script>
<!-- <script>impress().init();</script> -->
</body>
<html>