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<title>Octahedron challenge</title>
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<h1>Octahedron challenge</h1>
<p>Can you create something like this using <a href="https://jsxgraph.org/docs/symbols/Point3D.html#constructor"><code>Point3D</code></a> and <a href="https://jsxgraph.org/docs/symbols/Polygon3D.html#constructor"><code>Polygon3D</code></a> elements? Don’t worry about including the colors; they’re just to emphasize how the polygons fit together.</p>
<p>The <code>create</code> call for <code>Polygon3D</code> isn’t documented, but you can look at the polygon sampler for examples.</p>
<div id="octahedron-from-triangles" class="jxgbox" style="width:600px; height:600px"></div>
<!-- a solution to the octahedron challenge -->
<script type="text/javascript">
// to prevent variable name conflicts, we define variables locally using `let`
// and put the code for each board in its own block
{
// create a JSXGraph board and draw a 3D view on it
let board = JXG.JSXGraph.initBoard(
'octahedron-from-triangles',
{
boundingbox: [-8, 8, 8,-8],
axis: false,
showCopyright: false,
showNavigation: false
}
);
let view = board.create(
'view3d',
[[-4.5, -4.5], [9, 9],
[[0, 4], [0, 4], [0, 4]]],
{
xPlaneRear: {fillOpacity: 0.2, gradient: null},
yPlaneRear: {fillOpacity: 0.2, gradient: null},
zPlaneRear: {fillOpacity: 0.2, gradient: null},
depthOrderPoints: true
}
);
// create the vertices of the octahedron
let vertices = [];
coords = [
[1, 2, 2],
[3, 2, 2],
[2, 1, 2],
[2, 3, 2],
[2, 2, 1],
[2, 2, 3]
];
colors = [
'#f08',
'#4f0',
'#f60',
'#0af',
'#40f',
'#fb0'
];
for (i in coords) {
vertices.push(view.create(
'point3d',
coords[i],
{
withLabel: false,
size: 5,
strokeColor: 'none',
fillColor: 'white',
gradientSecondColor: colors[i],
highlightStrokeWidth: 1,
highlightStrokeColor: '#777'
}
));
}
// create the faces of the octahedron
view.create(
'polygon3d',
[vertices[0], vertices[2], vertices[5]],
{
fillColor: '#f85',
fillOpacity: 0.2,
borders: {
strokeWidth: 2,
strokeColor: '#f85',
highlightStrokeColor: '#777'
}
}
);
view.create(
'polygon3d',
[vertices[1], vertices[3], vertices[5]],
{
fillColor: '#af0',
fillOpacity: 0.2,
borders: {
strokeWidth: 2,
strokeColor: '#af0',
highlightStrokeColor: '#777'
}
}
);
view.create(
'polygon3d',
[vertices[0], vertices[3], vertices[4]],
{
fillColor: '#a0f',
fillOpacity: 0.2,
borders: {
strokeWidth: 2,
strokeColor: '#a0f',
highlightStrokeColor: '#777'
}
}
);
view.create(
'polygon3d',
[vertices[1], vertices[2], vertices[4]],
{
fillColor: '#a87',
fillOpacity: 0.2,
borders: {
strokeWidth: 2,
strokeColor: '#a87',
highlightStrokeColor: '#777'
}
}
);
}
</script>
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