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<title>3D polygon sampler</title>
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<h1>3D polygon sampler</h1>
<h2>Creating a polygon</h2>
<p>A polygon is created from a list of vertices. Each vertex is given either in coordinates or as a <a href="https://jsxgraph.org/docs/symbols/Point3D.html#constructor"><code>Point3D</code></a> element. The vertices that are created from coordinates are styled according to the <code>vertices</code> attribute. The edges of the polygon are styled according to the <code>borders</code> attribute.</p>
<p>To make the layout of the vertices easier to see, I’ve set the view’s <code>depthOrderPoints</code> attribute to <code>true</code>.
<div id="polygon-homog-board" class="jxgbox" style="width:600px; height:600px"></div>
<h2>Mixing coordinates and <code>Point3D</code> elements</h2>
<p>This example shows how you can mix coordinates and <a href="https://jsxgraph.org/docs/symbols/Point3D.html#constructor"><code>Point3D</code></a> elements in a polygon’s vertex list.</p>
<div id="polygon-mixed-board" class="jxgbox" style="width:600px; height:600px"></div>
<h2>Filling a polygon</h2>
<p>You can set the fill and opacity of a 3D polygon just like you would with a 2D polygon. I recommend only filling polygons that are guaranteed to stay planar. In this example, the polygons are always planar because they’re triangles.</p>
<div id="planar-fill-board" class="jxgbox" style="width:600px; height:600px"></div>
<h2>The pitalls of filling a non-planar polygon</h2>
<p>Make the polygon below non-planar by dragging its vertices. This will probably make the fill look really weird from certain angles.</p>
<div id="non-planar-fill-board" class="jxgbox" style="width:600px; height:600px"></div>
<!-- creating a polygon -->
<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(
'polygon-homog-board',
{
boundingbox: [-8, 8, 8,-8],
axis: false,
showCopyright: false,
showNavigation: false
}
);
let view = board.create(
'view3d',
[[-4.5, -4.5], [9, 9],
[[0, 3], [0, 3], [0, 3]]],
{
xPlaneRear: {fillOpacity: 0.2, gradient: null},
yPlaneRear: {fillOpacity: 0.2, gradient: null},
zPlaneRear: {fillOpacity: 0.2, gradient: null},
depthOrderPoints: true
}
);
// create a list of individually styled Point3D elements to use as the
// vertices of a polygon
let vertices1 = [];
coords1 = [
[2, 1, 1],
[2, 2, 1],
[1, 2, 1],
[1, 2, 2],
[1, 1, 2],
[1, 1, 1]
];
colors1 = [
'orangered',
'gold',
'mediumseagreen',
'darkturquoise',
'purple',
'deeppink'
];
for (i in coords1) {
vertices1.push(view.create(
'point3d',
coords1[i],
{
withLabel: false,
size: 5,
strokeColor: 'none',
fillColor: 'white',
gradientSecondColor: colors1[i],
highlightStrokeWidth: 1,
highlightStrokeColor: '#777'
}
));
}
// create a polygon from a list of vertices (given as Point3D elements)
let polygon1 = view.create(
'polygon3d',
vertices1,
{
borders: {
strokeColor: '#777',
highlightStrokeColor: '#999'
}
}
);
// create a polygon from a list of vertices (given in coordinates)
let coords2 = [
[0.5, 1.5, 1.5],
[1.5, 1.5, 1.5],
[1.5, 2.5, 1.5],
[0.5, 2.5, 1.5]
];
let polygon2 = view.create(
'polygon3d',
coords2,
{
vertices: {
withLabel: false,
strokeColor: 'none',
fillColor: 'white',
gradientSecondColor: '#444',
highlightStrokeWidth: 1,
highlightStrokeColor: 'black'
},
borders: {
strokeColor: 'black',
highlightStrokeColor: 'gray'
}
}
);
}
</script>
<!-- mixing coordinates and Point3D elements -->
<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(
'polygon-mixed-board',
{
boundingbox: [-8, 8, 8,-8],
axis: false,
showCopyright: false,
showNavigation: false
}
);
let view = board.create(
'view3d',
[[-4.5, -4.5], [9, 9],
[[0, 3], [0, 3], [0, 3]]],
{
xPlaneRear: {fillOpacity: 0.2, gradient: null},
yPlaneRear: {fillOpacity: 0.2, gradient: null},
zPlaneRear: {fillOpacity: 0.2, gradient: null},
depthOrderPoints: true
}
);
// create a list of individually styled Point3D elements to use as some
// vertices of a polygon
let vertices1 = [];
coords1 = [
[2, 1, 1],
[2, 2, 1],
[1, 2, 1],
[1, 2, 2],
[1, 1, 2],
[1, 1, 1]
];
colors1 = [
'orangered',
'gold',
'mediumseagreen',
'darkturquoise',
'purple',
'deeppink'
];
for (i in coords1) {
vertices1.push(view.create(
'point3d',
coords1[i],
{
withLabel: false,
size: 5,
strokeColor: 'none',
fillColor: 'white',
gradientSecondColor: colors1[i],
highlightStrokeWidth: 1,
highlightStrokeColor: '#777'
}
));
}
// list the coordinates of the other vertices of the polygon
let coords2 = [
[0.5, 1.5, 1.5],
[1.5, 1.5, 1.5],
[1.5, 2.5, 1.5],
[0.5, 2.5, 1.5]
];
// create a polygon from a list of vertices (some given in coordinates, and
// others given as Point3D elements)
let polygon = view.create(
'polygon3d',
vertices1.slice(0, 3).concat(coords2, vertices1.slice(3, 6)),
{
vertices: {
withLabel: false,
strokeColor: 'none',
fillColor: 'white',
gradientSecondColor: '#444',
highlightStrokeWidth: 1,
highlightStrokeColor: 'black'
},
borders: {
strokeColor: 'black',
highlightStrokeColor: 'gray'
}
}
);
}
</script>
<!-- filling a polygon -->
<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(
'planar-fill-board',
{
boundingbox: [-8, 8, 8,-8],
axis: false,
showCopyright: false,
showNavigation: false
}
);
let view = board.create(
'view3d',
[[-4.5, -4.5], [9, 9],
[[0, 3], [0, 3], [0, 3]]],
{
xPlaneRear: {fillOpacity: 0.2, gradient: null},
yPlaneRear: {fillOpacity: 0.2, gradient: null},
zPlaneRear: {fillOpacity: 0.2, gradient: null},
depthOrderPoints: true
}
);
// create a list of individually styled Point3D elements to use as polygon
// vertices
let vertices = [];
coords = [
[2, 0.5, 0.5],
[0.5, 2, 0.5],
[0.5, 0.5, 2],
[0.5, 1.25, 1.25],
[1.25, 0.5, 1.25],
[1.25, 1.25, 0.5]
];
colors = [
'#f08',
'#fb0',
'#0af',
'#4f0',
'#80f',
'#f60'
];
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 some filled triangles
view.create(
'polygon3d',
[vertices[0], vertices[5], vertices[4]],
{
fillColor: '#f85',
fillOpacity: 0.4,
borders: {strokeColor: 'none'}
}
);
view.create(
'polygon3d',
[vertices[1], vertices[3], vertices[5]],
{
fillColor: '#af0',
fillOpacity: 0.4,
borders: {strokeColor: 'none'}
}
);
view.create(
'polygon3d',
[vertices[2], vertices[3], vertices[4]],
{
fillColor: '#64f',
fillOpacity: 0.4,
borders: {strokeColor: 'none'}
}
);
view.create(
'polygon3d',
[vertices[3], vertices[4], vertices[5]],
{
fillColor: '#a87',
fillOpacity: 0.4,
borders: {strokeColor: 'none'}
}
);
}
</script>
<!-- the pitfalls of filling a non-planar polygon -->
<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(
'non-planar-fill-board',
{
boundingbox: [-8, 8, 8,-8],
axis: false,
showCopyright: false,
showNavigation: false
}
);
let view = board.create(
'view3d',
[[-4.5, -4.5], [9, 9],
[[0, 3], [0, 3], [0, 3]]],
{
xPlaneRear: {fillOpacity: 0.2, gradient: null},
yPlaneRear: {fillOpacity: 0.2, gradient: null},
zPlaneRear: {fillOpacity: 0.2, gradient: null},
depthOrderPoints: true
}
);
// create a list of individually styled Point3D elements to use as polygon
// vertices
let vertices = [];
coords = [
[2, 0.5, 0.5],
[0.5, 2, 0.5],
[0.5, 0.5, 2],
[0.5, 1.25, 1.25],
[1.25, 0.5, 1.25],
[1.25, 1.25, 0.5]
];
colors = [
'#f08',
'#fb0',
'#0af',
'#4f0',
'#80f',
'#f60'
];
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 a filled polygon that can become non-planar
view.create(
'polygon3d',
[vertices[0], vertices[5], vertices[1], vertices[3], vertices[2], vertices[4]],
{
fillColor: '#a87',
fillOpacity: 0.4,
borders: {strokeColor: 'none'}
}
);
}
</script>
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</html>