hollasch/.block

## .block
height: 960

## README.md

      
    Raw
  

              README.md
            
          
    This example renders a loose enclosing hull around a scattered set of points using a rounded
Catmull-Rom curve. A strict convex hull is computed using D3.polygonHull, offset by a specified
amount, and then interpolated with a closed curve.
See also the same basic approach using straight segments and circular arcs:
Rounded Enclosing Hull.

  
## index.html
<!DOCTYPE html>
<meta charset="utf-8">
<style>
    svg {
        background-color: #cccccc;
        border: 2px solid #777777;
        margin: 20px;
    }
</style>


<script src="http://d3js.org/d3.v4.js"></script>

<svg id="demo" width='900' height='900'></svg>

<script>

// =============================================================================
// Smooth Hull Generation using D3
// =============================================================================

// Setup and Parameterization

var svg = d3.select('svg#demo');

var width = svg.attr('width');
var height = svg.attr('height');

var pointRadius = 20;
var hullPadding = 60;


// Point/Vector Operations

var vecFrom = function (p0, p1) {               // Vector from p0 to p1
    return [ p1[0] - p0[0], p1[1] - p0[1] ];
}

var vecScale = function (v, scale) {            // Vector v scaled by 'scale'
    return [ scale * v[0], scale * v[1] ];
}

var vecSum = function (pv1, pv2) {              // The sum of two points/vectors
    return [ pv1[0] + pv2[0], pv1[1] + pv2[1] ];
}

var vecUnit = function (v) {                    // Vector with direction of v and length 1
    var norm = Math.sqrt (v[0]*v[0] + v[1]*v[1]);
    return vecScale (v, 1/norm);
}

var vecScaleTo = function (v, length) {         // Vector with direction of v with specified length
    return vecScale (vecUnit(v), length);
}

var unitNormal = function (pv0, p1) {           // Unit normal to vector pv0, or line segment from p0 to p1
    if (p1 != null) pv0 = vecFrom (pv0, p1);
    var normalVec = [ -pv0[1], pv0[0] ];
    return vecUnit (normalVec);
};


// Hull Generators

var lineFn = d3.line()
    .curve (d3.curveCatmullRomClosed)
    .x (function(d) { return d.p[0]; })
    .y (function(d) { return d.p[1]; });


var smoothHull = function (polyPoints) {
    // Returns the SVG path data string representing the polygon, expanded and smoothed.

    var pointCount = polyPoints.length;

    // Handle special cases
    if (!polyPoints || pointCount < 1) return "";
    if (pointCount === 1) return smoothHull1 (polyPoints);
    if (pointCount === 2) return smoothHull2 (polyPoints);

    var hullPoints = polyPoints.map (function (point, index) {
        var pNext = polyPoints [(index + 1) % pointCount];
        return {
            p: point,
            v: vecUnit (vecFrom (point, pNext))
        };
    });

    // Compute the expanded hull points, and the nearest prior control point for each.
    for (var i = 0;  i < hullPoints.length;  ++i) {
        var priorIndex = (i > 0) ? (i-1) : (pointCount - 1);
        var extensionVec = vecUnit (vecSum (hullPoints[priorIndex].v, vecScale (hullPoints[i].v, -1)));
        hullPoints[i].p = vecSum (hullPoints[i].p, vecScale (extensionVec, hullPadding));
    }

    return lineFn (hullPoints);
}


var smoothHull1 = function (polyPoints) {
    // Returns the path for a circular hull around a single point.

    var p1 = [polyPoints[0][0], polyPoints[0][1] - hullPadding];
    var p2 = [polyPoints[0][0], polyPoints[0][1] + hullPadding];

    return 'M ' + p1
        + ' A ' + [hullPadding, hullPadding, '0,0,0', p2].join(',')
        + ' A ' + [hullPadding, hullPadding, '0,0,0', p1].join(',');
};


var smoothHull2 = function (polyPoints) {
    // Returns the path for a rounded hull around two points.

    var v = vecFrom (polyPoints[0], polyPoints[1]);
    var extensionVec = vecScaleTo(v, hullPadding);

    var extension0 = vecSum (polyPoints[0], vecScale(extensionVec, -1));
    var extension1 = vecSum (polyPoints[1], extensionVec);

    var tangentHalfLength = 1.2 * hullPadding;
    var controlDelta    = vecScaleTo (unitNormal(v), tangentHalfLength);
    var invControlDelta = vecScale (controlDelta, -1);

    var control0 = vecSum (extension0, invControlDelta);
    var control1 = vecSum (extension1, invControlDelta);
    var control3 = vecSum (extension0, controlDelta);

    return 'M ' + extension0
        + ' C ' + [control0, control1, extension1].join(',')
        + ' S ' + [          control3, extension0].join(',')
        + ' Z';
};


// Initial Graphics Setup

var convexHullPath = svg.append('path')
    .attr ('fill', '#aca')
    .attr ('stroke', '#888')
    .attr ('stroke-width', '6px');


function render (points) {
    var convexHull = (points.length < 3) ? points : d3.polygonHull(points);

    var points = svg
        .selectAll ('circle')
        .data (points, function pointId(d) { return d[2]; });

    points.enter()
        .append ('circle')
        .attr ('fill', '#a8d')
        .attr ('stroke', 'black')
        .attr ('stroke-width', '2px')
        .attr ('r', pointRadius)
        .attr ('cx', function(d) { return d[0]; })
        .attr ('cy', function(d) { return d[1]; });

    points.exit()
        .remove();

    convexHullPath.attr ('d', smoothHull(convexHull));
}


// Random point generators
var margin = hullPadding + pointRadius;
var pointGenX = d3.randomUniform (margin, width  - margin);
var pointGenY = d3.randomUniform (margin, height - margin);
var pointGen = function (id) { return [pointGenX(), pointGenY(), id]; };

var minPointCount = 1;
var maxPointCount = 12;
var pointId = 0;
var addPoints = true;
var points = d3.range(minPointCount - 1).map(pointGen);

var updateFunction = function() {
    if (addPoints) {
        points.push (pointGen(++pointId));
        addPoints = (points.length < maxPointCount);
    } else {
        var i = Number.parseInt (Math.random() * points.length);
        points.splice (i, 1);
        addPoints = (points.length <= minPointCount);
    }

    render (points);
    window.setTimeout (updateFunction, 500);
};

updateFunction();    // Launch the animation

</script>

## LICENSE.txt
MIT License

Copyright © 2017 Steve Hollasch

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.imitations under the License.

## preview.png

      
    Raw
  

              preview.png
            
          
## thumbnail.png

      
    Raw
  

              thumbnail.png
	<!DOCTYPE html>
	<meta charset="utf-8">
	<style>
	svg {
	background-color: #cccccc;
	border: 2px solid #777777;
	margin: 20px;
	}
	</style>


	<script src="http://d3js.org/d3.v4.js"></script>

	<svg id="demo" width='900' height='900'></svg>

	<script>

	// =============================================================================
	// Smooth Hull Generation using D3
	// =============================================================================

	// Setup and Parameterization

	var svg = d3.select('svg#demo');

	var width = svg.attr('width');
	var height = svg.attr('height');

	var pointRadius = 20;
	var hullPadding = 60;


	// Point/Vector Operations

	var vecFrom = function (p0, p1) { // Vector from p0 to p1
	return [ p1[0] - p0[0], p1[1] - p0[1] ];
	}

	var vecScale = function (v, scale) { // Vector v scaled by 'scale'
	return [ scale * v[0], scale * v[1] ];
	}

	var vecSum = function (pv1, pv2) { // The sum of two points/vectors
	return [ pv1[0] + pv2[0], pv1[1] + pv2[1] ];
	}

	var vecUnit = function (v) { // Vector with direction of v and length 1
	var norm = Math.sqrt (v[0]v[0] + v[1]v[1]);
	return vecScale (v, 1/norm);
	}

	var vecScaleTo = function (v, length) { // Vector with direction of v with specified length
	return vecScale (vecUnit(v), length);
	}

	var unitNormal = function (pv0, p1) { // Unit normal to vector pv0, or line segment from p0 to p1
	if (p1 != null) pv0 = vecFrom (pv0, p1);
	var normalVec = [ -pv0[1], pv0[0] ];
	return vecUnit (normalVec);
	};


	// Hull Generators

	var lineFn = d3.line()
	.curve (d3.curveCatmullRomClosed)
	.x (function(d) { return d.p[0]; })
	.y (function(d) { return d.p[1]; });


	var smoothHull = function (polyPoints) {
	// Returns the SVG path data string representing the polygon, expanded and smoothed.

	var pointCount = polyPoints.length;

	// Handle special cases
	if (!polyPoints \|\| pointCount < 1) return "";
	if (pointCount === 1) return smoothHull1 (polyPoints);
	if (pointCount === 2) return smoothHull2 (polyPoints);

	var hullPoints = polyPoints.map (function (point, index) {
	var pNext = polyPoints [(index + 1) % pointCount];
	return {
	p: point,
	v: vecUnit (vecFrom (point, pNext))
	};
	});

	// Compute the expanded hull points, and the nearest prior control point for each.
	for (var i = 0; i < hullPoints.length; ++i) {
	var priorIndex = (i > 0) ? (i-1) : (pointCount - 1);
	var extensionVec = vecUnit (vecSum (hullPoints[priorIndex].v, vecScale (hullPoints[i].v, -1)));
	hullPoints[i].p = vecSum (hullPoints[i].p, vecScale (extensionVec, hullPadding));
	}

	return lineFn (hullPoints);
	}


	var smoothHull1 = function (polyPoints) {
	// Returns the path for a circular hull around a single point.

	var p1 = [polyPoints[0][0], polyPoints[0][1] - hullPadding];
	var p2 = [polyPoints[0][0], polyPoints[0][1] + hullPadding];

	return 'M ' + p1
	+ ' A ' + [hullPadding, hullPadding, '0,0,0', p2].join(',')
	+ ' A ' + [hullPadding, hullPadding, '0,0,0', p1].join(',');
	};


	var smoothHull2 = function (polyPoints) {
	// Returns the path for a rounded hull around two points.

	var v = vecFrom (polyPoints[0], polyPoints[1]);
	var extensionVec = vecScaleTo(v, hullPadding);

	var extension0 = vecSum (polyPoints[0], vecScale(extensionVec, -1));
	var extension1 = vecSum (polyPoints[1], extensionVec);

	var tangentHalfLength = 1.2 * hullPadding;
	var controlDelta = vecScaleTo (unitNormal(v), tangentHalfLength);
	var invControlDelta = vecScale (controlDelta, -1);

	var control0 = vecSum (extension0, invControlDelta);
	var control1 = vecSum (extension1, invControlDelta);
	var control3 = vecSum (extension0, controlDelta);

	return 'M ' + extension0
	+ ' C ' + [control0, control1, extension1].join(',')
	+ ' S ' + [ control3, extension0].join(',')
	+ ' Z';
	};


	// Initial Graphics Setup

	var convexHullPath = svg.append('path')
	.attr ('fill', '#aca')
	.attr ('stroke', '#888')
	.attr ('stroke-width', '6px');


	function render (points) {
	var convexHull = (points.length < 3) ? points : d3.polygonHull(points);

	var points = svg
	.selectAll ('circle')
	.data (points, function pointId(d) { return d[2]; });

	points.enter()
	.append ('circle')
	.attr ('fill', '#a8d')
	.attr ('stroke', 'black')
	.attr ('stroke-width', '2px')
	.attr ('r', pointRadius)
	.attr ('cx', function(d) { return d[0]; })
	.attr ('cy', function(d) { return d[1]; });

	points.exit()
	.remove();

	convexHullPath.attr ('d', smoothHull(convexHull));
	}


	// Random point generators
	var margin = hullPadding + pointRadius;
	var pointGenX = d3.randomUniform (margin, width - margin);
	var pointGenY = d3.randomUniform (margin, height - margin);
	var pointGen = function (id) { return [pointGenX(), pointGenY(), id]; };

	var minPointCount = 1;
	var maxPointCount = 12;
	var pointId = 0;
	var addPoints = true;
	var points = d3.range(minPointCount - 1).map(pointGen);

	var updateFunction = function() {
	if (addPoints) {
	points.push (pointGen(++pointId));
	addPoints = (points.length < maxPointCount);
	} else {
	var i = Number.parseInt (Math.random() * points.length);
	points.splice (i, 1);
	addPoints = (points.length <= minPointCount);
	}

	render (points);
	window.setTimeout (updateFunction, 500);
	};

	updateFunction(); // Launch the animation

	</script>
	MIT License

	Copyright © 2017 Steve Hollasch

	Permission is hereby granted, free of charge, to any person obtaining a copy
	of this software and associated documentation files (the "Software"), to deal
	in the Software without restriction, including without limitation the rights
	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	copies of the Software, and to permit persons to whom the Software is
	furnished to do so, subject to the following conditions:

	The above copyright notice and this permission notice shall be included in all
	copies or substantial portions of the Software.

	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
	SOFTWARE.imitations under the License.