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patricksurry/README.md

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Last active March 28, 2023 23:31
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Flying arcs with height proportional to length
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README.md

Adapted from this, to avoid the second projection and make flying arc height proportional to length.

Because the 'sky' projection is just a scaled up version of the original one, the projection of a sky point in canvas coords can be easily calculated by scaling the ground projection point along the vector from the origin.

Another improvement(?) might be to avoid the swoosh/interpolate function by doing this same trick directly on the stream of points that comes from the normal projection path function.

Raw
index.html
<!DOCTYPE html>
<meta charset="utf-8">
<style>
.land {
fill: #999;
stroke-opacity: 1;
}
.graticule {
fill: none;
stroke: black;
stroke-width:.5;
opacity:.2;
}
.labels {
font: 8px sans-serif;
fill: black;
opacity: .5;
display:none;
}
.noclicks { pointer-events:none; }
.point { opacity:.6; }
.arcs {
opacity:.1;
stroke: gray;
stroke-width: 3;
}
.flyers {
stroke-width:1;
opacity: .6;
stroke: darkred;
}
.arc, .flyer {
stroke-linejoin: round;
fill:none;
}
.arc { }
.flyer { }
.flyer:hover { }
</style>
<body>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script src="http://d3js.org/queue.v1.min.js"></script>
<script src="http://d3js.org/topojson.v0.min.js"></script>
<script>
d3.select(window)
.on("mousemove", mousemove)
.on("mouseup", mouseup);
var width = 960,
height = 500;
var proj = d3.geo.orthographic()
.translate([width / 2, height / 2])
.clipAngle(90)
.scale(220);
var path = d3.geo.path().projection(proj).pointRadius(2);
var swoosh = d3.svg.line()
.x(function(d) { return d[0] })
.y(function(d) { return d[1] })
.interpolate("cardinal")
.tension(.0);
var links = [],
arcLines = [];
var svg = d3.select("body").append("svg")
.attr("width", width)
.attr("height", height)
.on("mousedown", mousedown);
queue()
.defer(d3.json, "world-110m.json")
.defer(d3.json, "places.json")
.await(ready);
function ready(error, world, places) {
var ocean_fill = svg.append("defs").append("radialGradient")
.attr("id", "ocean_fill")
.attr("cx", "75%")
.attr("cy", "25%");
ocean_fill.append("stop").attr("offset", "5%").attr("stop-color", "#fff");
ocean_fill.append("stop").attr("offset", "100%").attr("stop-color", "#ababab");
var globe_highlight = svg.append("defs").append("radialGradient")
.attr("id", "globe_highlight")
.attr("cx", "75%")
.attr("cy", "25%");
globe_highlight.append("stop")
.attr("offset", "5%").attr("stop-color", "#ffd")
.attr("stop-opacity","0.6");
globe_highlight.append("stop")
.attr("offset", "100%").attr("stop-color", "#ba9")
.attr("stop-opacity","0.2");
var globe_shading = svg.append("defs").append("radialGradient")
.attr("id", "globe_shading")
.attr("cx", "55%")
.attr("cy", "45%");
globe_shading.append("stop")
.attr("offset","30%").attr("stop-color", "#fff")
.attr("stop-opacity","0")
globe_shading.append("stop")
.attr("offset","100%").attr("stop-color", "#505962")
.attr("stop-opacity","0.3")
var drop_shadow = svg.append("defs").append("radialGradient")
.attr("id", "drop_shadow")
.attr("cx", "50%")
.attr("cy", "50%");
drop_shadow.append("stop")
.attr("offset","20%").attr("stop-color", "#000")
.attr("stop-opacity",".5")
drop_shadow.append("stop")
.attr("offset","100%").attr("stop-color", "#000")
.attr("stop-opacity","0")
svg.append("ellipse")
.attr("cx", 440).attr("cy", 450)
.attr("rx", proj.scale()*.90)
.attr("ry", proj.scale()*.25)
.attr("class", "noclicks")
.style("fill", "url(#drop_shadow)");
svg.append("circle")
.attr("cx", width / 2).attr("cy", height / 2)
.attr("r", proj.scale())
.attr("class", "noclicks")
.style("fill", "url(#ocean_fill)");
svg.append("path")
.datum(topojson.object(world, world.objects.land))
.attr("class", "land noclicks")
.attr("d", path);
svg.append("circle")
.attr("cx", width / 2).attr("cy", height / 2)
.attr("r", proj.scale())
.attr("class","noclicks")
.style("fill", "url(#globe_highlight)");
svg.append("circle")
.attr("cx", width / 2).attr("cy", height / 2)
.attr("r", proj.scale())
.attr("class","noclicks")
.style("fill", "url(#globe_shading)");
svg.append("g").attr("class","points")
.selectAll("text").data(places.features)
.enter().append("path")
.attr("class", "point")
.attr("d", path);
// spawn links between cities as source/target coord pairs
places.features.forEach(function(a) {
places.features.forEach(function(b) {
if (a !== b) {
links.push({
source: a.geometry.coordinates,
target: b.geometry.coordinates
});
}
});
});
// build geoJSON features from links array
links.forEach(function(e,i,a) {
var feature = { "type": "Feature", "geometry": { "type": "LineString", "coordinates": [e.source,e.target] }}
arcLines.push(feature)
})
svg.append("g").attr("class","arcs")
.selectAll("path").data(arcLines)
.enter().append("path")
.attr("class","arc")
.attr("d",path)
svg.append("g").attr("class","flyers")
.selectAll("path").data(links)
.enter().append("path")
.attr("class","flyer")
.attr("d", function(d) { return swoosh(flying_arc(d)) })
refresh();
}
function flying_arc(pts) {
var source = pts.source,
target = pts.target;
// get canvas coords of arc midpoint and globe center
var mid = proj(location_along_arc(source, target, .5));
var ctr = proj.translate();
// max length of a great circle arc is π,
// so 0.3 means longest path "flies" 20% of radius above the globe
var scale = 1 + 0.3 * d3.geo.distance(source,target) / Math.PI;
mid[0] = ctr[0] + (mid[0]-ctr[0])*scale;
mid[1] = ctr[1] + (mid[1]-ctr[1])*scale;
var result = [ proj(source),
mid,
proj(target) ]
return result;
}
function refresh() {
svg.selectAll(".land").attr("d", path);
svg.selectAll(".point").attr("d", path);
svg.selectAll(".arc").attr("d", path)
.attr("opacity", function(d) {
return fade_at_edge(d)
})
svg.selectAll(".flyer")
.attr("d", function(d) { return swoosh(flying_arc(d)) })
.attr("opacity", function(d) {
return fade_at_edge(d)
})
}
function fade_at_edge(d) {
var centerPos = proj.invert([width/2,height/2]),
arc = d3.geo.greatArc(),
start, end;
// function is called on 2 different data structures..
if (d.source) {
start = d.source,
end = d.target;
}
else {
start = d.geometry.coordinates[0];
end = d.geometry.coordinates[1];
}
var start_dist = 1.57 - arc.distance({source: start, target: centerPos}),
end_dist = 1.57 - arc.distance({source: end, target: centerPos});
var fade = d3.scale.linear().domain([-.1,0]).range([0,.1])
var dist = start_dist < end_dist ? start_dist : end_dist;
return fade(dist)
}
function location_along_arc(start, end, loc) {
var interpolator = d3.geo.interpolate(start,end);
return interpolator(loc)
}
// modified from http://bl.ocks.org/1392560
var m0, o0;
function mousedown() {
m0 = [d3.event.pageX, d3.event.pageY];
o0 = proj.rotate();
d3.event.preventDefault();
}
function mousemove() {
if (m0) {
var m1 = [d3.event.pageX, d3.event.pageY]
, o1 = [o0[0] + (m1[0] - m0[0]) / 6, o0[1] + (m0[1] - m1[1]) / 6];
o1[1] = o1[1] > 30 ? 30 :
o1[1] < -30 ? -30 :
o1[1];
proj.rotate(o1);
refresh();
}
}
function mouseup() {
if (m0) {
mousemove();
m0 = null;
}
}
</script>
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places.json
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world-110m.json
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@Sheraff
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Sheraff commented Dec 16, 2014

Is this much faster than the original one? I'm starting a small project (https://github.com/Sheraff/torrent-propagation-visualizer) that would potentially have more than a thousand points... Very heavy! ;-)

@sirallen
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Is there a straightforward way to "clip" the arcs instead of doing the fade effect?

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