I use this as reference: https://bl.ocks.org/iamkevinv/0a24e9126cd2fa6b283c6f2d774b69a2
Adjusted some syntax to fit for version 5
Scale works, Translate looks like it works too because if I change the value, it zooms on different place..
But the problem is it doesn't zoom on the correct place I clicked.
I think this doesn't get to the place correctly because I use d3.geoMercator().fitSize([width, height], geoJSONFeatures) instead:
var bounds = path.bounds(d),
dx = bounds[1][0] - bounds[0][0],
dy = bounds[1][1] - bounds[0][1],
x = (bounds[0][0] + bounds[1][0]) / 2,
y = (bounds[0][1] + bounds[1][1]) / 2,
scale = Math.max(1, Math.min(8, 0.9 / Math.max(dx / width, dy / height))),
translate = [width / 2 - scale * x, height / 2 - scale * y];
Already tried to change the values to fit mine but failed, I can't get it.
Here is my projection:
var width = 500;
var height = 600;
d3.json("/regions50mtopo.json")
.then((geoJSON) => {
var geoJSONFeatures = topojson.feature(geoJSON, geoJSON.objects["Regions.50m"]);
// My Projection
var projection = d3.geoMercator().fitSize([width, height], geoJSONFeatures);
...
Any help, guide or reference?
Note: I'm mapping different country and fitSize(...) solves the
problem easily to fit on my svg that's why I can't use the same as in
the reference link I provided.
Found an answer: https://bl.ocks.org/veltman/77679636739ea2fc6f0be1b4473cf03a
centered = centered !== d && d;
var paths = svg.selectAll("path")
.classed("active", d => d === centered);
// Starting translate/scale
var t0 = projection.translate(),
s0 = projection.scale();
// Re-fit to destination
projection.fitSize([960, 500], centered || states);
// Create interpolators
var interpolateTranslate = d3.interpolate(t0, projection.translate()),
interpolateScale = d3.interpolate(s0, projection.scale());
var interpolator = function(t) {
projection.scale(interpolateScale(t))
.translate(interpolateTranslate(t));
paths.attr("d", path);
};
d3.transition()
.duration(750)
.tween("projection", function() {
return interpolator;
});
Exactly what I'm looking for. It works now as expected.
But maybe somebody also have suggestions on how to optimise it, because as the author said too, it feels slow and "laggy" when zooming in/out.
I am building a map in d3 and basing it off of this codepen by Andy Barefoot: https://codepen.io/nb123456/pen/zLdqvM?editors=0010. I want to modify the initiateZoom() function so that if I set the lat/lon coordinates for a box surrounding say Ohio, the map will initialize its panning to be over Ohio.
function initiateZoom() {
minZoom = Math.max($("#map-holder").width() / w, $("#map-holder").height() / h);
maxZoom = 20 * minZoom;
zoom
.scaleExtent([minZoom, maxZoom])
.translateExtent([[0, 0], [w, h]])
;
midX = ($("#map-holder").width() - minZoom * w) / 2;
midY = ($("#map-holder").height() - minZoom * h) / 2;//These are the original values
var swlat = 32;
var swlon = -82;
var nelat = 42;
var nelon = -72;
var projectCoordinates = projection([(swlat+nelat)/2, (swlon+nelon)/2]);
/*This did not work
var midX = minZoom*(w-(swlat+nelat)/2) - ($("#map-holder").width()-(swlat+nelat)/2);
var midY = minZoom*(h-(swlon+nelon)/2) - ($("#map-holder").height()-(swlon+nelon)/2);*/
/*Neither did this
var midX = minZoom*(w-projectCoordinates[0])-($("#map-holder").width()-projectCoordinates[0]);
var midY = minZoom*(h-projectCoordinates[1])-($("#map-holder").height()-projectCoordinates[1]);*/
svg.call(zoom.transform, d3.zoomIdentity.translate(midX, midY).scale(minZoom));
}
The idea behind the original approach was to:
1: Get the current pixel display of the map
2: Get the new pixel distance from the map corner to the map point after zoom has been applied
3: The pixel distance of the center of the container to the top of the container
4: subtract the values from 2 and 3
The original post was trying to translate the map so that it would initialize the zoom and pan over the center of the map. I tried to modify this approach first by directly substituting the lat/lon values into the above equations. I also tried first transforming the lat/lon values using the projection and then substituting those values in, with little success. What do I need to do in order to get my desired result?
Setting a translateExtent could be a bad idea because it depends on the zoom scale.
The following replacement works.
function initiateZoom() {
// Define a "minzoom" whereby the "Countries" is as small possible without leaving white space at top/bottom or sides
minZoom = Math.max($("#map-holder").width() / w, $("#map-holder").height() / h);
// set max zoom to a suitable factor of this value
maxZoom = 20 * minZoom;
// set extent of zoom to chosen values
// set translate extent so that panning can't cause map to move out of viewport
zoom
.scaleExtent([minZoom, maxZoom])
.translateExtent([[0, 0], [w, h]])
;
var swlat = 32;
var swlon = -82;
var nelat = 42;
var nelon = -72;
var nwXY = projection([swlon, nelat]);
var seXY = projection([nelon, swlat]);
var zoomScale = Math.min($("#map-holder").width()/(seXY[0]-nwXY[0]), $("#map-holder").height()/(seXY[1]-nwXY[1]))
var projectCoordinates = projection([(swlon+nelon)/2, (swlat+nelat)/2]);
svg.call(zoom.transform, d3.zoomIdentity.translate($("#map-holder").width()*0.5-zoomScale*projectCoordinates[0], $("#map-holder").height()*0.5-zoomScale*projectCoordinates[1]).scale(zoomScale));
}
I'm trying to optimize a Mapbox view for long-distance hiking trails, like the Appalachian Trail or the Pacific Crest Trail. Here's an example, which I've oriented by hand, showing the Senda Pirenáica in Spain:
The area of interest, the viewport, and the pitch are given. I need to find the correct center, bearing, and zoom.
The map.fitBounds method doesn't help me here because it assumes pitch=0 and bearing=0.
I've done some poking around and this seems to be a variation of the smallest surrounding rectangle problem, but I'm stuck on a couple of additional complications:
How do I account for the distorting effect of pitch?
How do I optimize for the aspect ratio of the viewport? Note that taking the viewport narrower or wider would change the bearing of the best solution:
FWIW I'm also using turf-js, which helps me get the convex hull for the line.
This solution results in the path displayed at the correct bearing with a magenta trapezoid outline showing the target "tightest trapezoid" to show the results of the calculations. The extra line coming from the top corner shows where the map.center() value is located.
The approach is as follows:
render the path to the map using the "fitbounds" technique to get an approximate zoom level for the "north up and pitch=0" situation
rotate the pitch to the desired angle
grab the trapezoid from the canvas
This result would look like this:
After this, we want to rotate that trapezoid around the path and find the tightest fit of the trapezoid to the points. In order to test for the tightest fit it is easier to rotate the path rather than the trapezoid so I have taken that approach here. I haven't implemented a "convex hull" on the path to minimize the number of points to rotate but that is something that can be added as an optimization step.
To get the tightest fit, the first step is to move the map.center() so that the path is at the "back" of the view. This is where the most space is in the frustum so it will be easy to manipulate it there:
Next, we measure the distance between the angled trapezoid walls and each point in the path, saving the closest points on both the left and right sides. We then center the path in the view by translating the view horizontally based on these distances, and then scale the view to eliminate that space on both sides as shown by the green trapezoid below:
The scale used to get this "tightest fit" gives us our ranking for whether this is the best view of the path. However, this view may not be the best visually since we pushed the path to the back of the view to determine the ranking. Instead, we now adjust the view to place the path in the vertical center of the view, and scale the view triangle larger accordingly. This gives us the magenta colored "final" view desired:
Finally, this process is done for every degree and the minimum scale value determines the winning bearing, and we take the associated scale and center position from there.
mapboxgl.accessToken = 'pk.eyJ1IjoiZm1hY2RlZSIsImEiOiJjajJlNWMxenowNXU2MzNudmkzMndwaGI3In0.ALOYWlvpYXnlcH6sCR9MJg';
var map;
var myPath = [
[-122.48369693756104, 37.83381888486939],
[-122.48348236083984, 37.83317489144141],
[-122.48339653015138, 37.83270036637107],
[-122.48356819152832, 37.832056363179625],
[-122.48404026031496, 37.83114119107971],
[-122.48404026031496, 37.83049717427869],
[-122.48348236083984, 37.829920943955045],
[-122.48356819152832, 37.82954808664175],
[-122.48507022857666, 37.82944639795659],
[-122.48610019683838, 37.82880236636284],
[-122.48695850372314, 37.82931081282506],
[-122.48700141906738, 37.83080223556934],
[-122.48751640319824, 37.83168351665737],
[-122.48803138732912, 37.832158048267786],
[-122.48888969421387, 37.83297152392784],
[-122.48987674713133, 37.83263257682617],
[-122.49043464660643, 37.832937629287755],
[-122.49125003814696, 37.832429207817725],
[-122.49163627624512, 37.832564787218985],
[-122.49223709106445, 37.83337825839438],
[-122.49378204345702, 37.83368330777276]
];
var myPath2 = [
[-122.48369693756104, 37.83381888486939],
[-122.49378204345702, 37.83368330777276]
];
function addLayerToMap(name, points, color, width) {
map.addLayer({
"id": name,
"type": "line",
"source": {
"type": "geojson",
"data": {
"type": "Feature",
"properties": {},
"geometry": {
"type": "LineString",
"coordinates": points
}
}
},
"layout": {
"line-join": "round",
"line-cap": "round"
},
"paint": {
"line-color": color,
"line-width": width
}
});
}
function Mercator2ll(mercX, mercY) {
var rMajor = 6378137; //Equatorial Radius, WGS84
var shift = Math.PI * rMajor;
var lon = mercX / shift * 180.0;
var lat = mercY / shift * 180.0;
lat = 180 / Math.PI * (2 * Math.atan(Math.exp(lat * Math.PI / 180.0)) - Math.PI / 2.0);
return [ lon, lat ];
}
function ll2Mercator(lon, lat) {
var rMajor = 6378137; //Equatorial Radius, WGS84
var shift = Math.PI * rMajor;
var x = lon * shift / 180;
var y = Math.log(Math.tan((90 + lat) * Math.PI / 360)) / (Math.PI / 180);
y = y * shift / 180;
return [ x, y ];
}
function convertLL2Mercator(points) {
var m_points = [];
for(var i=0;i<points.length;i++) {
m_points[i] = ll2Mercator( points[i][0], points[i][1] );
}
return m_points;
}
function convertMercator2LL(m_points) {
var points = [];
for(var i=0;i<m_points.length;i++) {
points[i] = Mercator2ll( m_points[i][0], m_points[i][1] );;
}
return points;
}
function pointsTranslate(points,xoff,yoff) {
var newpoints = [];
for(var i=0;i<points.length;i++) {
newpoints[i] = [ points[i][0] + xoff, points[i][1] + yoff ];
}
return(newpoints);
}
// note [0] elements are lng [1] are lat
function getBoundingBox(arr) {
var ne = [ arr[0][0] , arr[0][1] ];
var sw = [ arr[0][0] , arr[0][1] ];
for(var i=1;i<arr.length;i++) {
if(ne[0] < arr[i][0]) ne[0] = arr[i][0];
if(ne[1] < arr[i][1]) ne[1] = arr[i][1];
if(sw[0] > arr[i][0]) sw[0] = arr[i][0];
if(sw[1] > arr[i][1]) sw[1] = arr[i][1];
}
return( [ sw, ne ] );
}
function pointsRotate(points, cx, cy, angle){
var radians = angle * Math.PI / 180.0;
var cos = Math.cos(radians);
var sin = Math.sin(radians);
var newpoints = [];
function rotate(x, y) {
var nx = cx + (cos * (x - cx)) + (-sin * (y - cy));
var ny = cy + (cos * (y - cy)) + (sin * (x - cx));
return [nx, ny];
}
for(var i=0;i<points.length;i++) {
newpoints[i] = rotate(points[i][0],points[i][1]);
}
return(newpoints);
}
function convertTrapezoidToPath(trap) {
return([
[trap.Tl.lng, trap.Tl.lat], [trap.Tr.lng, trap.Tr.lat],
[trap.Br.lng, trap.Br.lat], [trap.Bl.lng, trap.Bl.lat],
[trap.Tl.lng, trap.Tl.lat] ]);
}
function getViewTrapezoid() {
var canvas = map.getCanvas();
var trap = {};
trap.Tl = map.unproject([0,0]);
trap.Tr = map.unproject([canvas.offsetWidth,0]);
trap.Br = map.unproject([canvas.offsetWidth,canvas.offsetHeight]);
trap.Bl = map.unproject([0,canvas.offsetHeight]);
return(trap);
}
function pointsScale(points,cx,cy, scale) {
var newpoints = []
for(var i=0;i<points.length;i++) {
newpoints[i] = [ cx + (points[i][0]-cx)*scale, cy + (points[i][1]-cy)*scale ];
}
return(newpoints);
}
var id = 1000;
function convertMercator2LLAndDraw(m_points, color, thickness) {
var newpoints = convertMercator2LL(m_points);
addLayerToMap("id"+id++, newpoints, color, thickness);
}
function pointsInTrapezoid(points,yt,yb,xtl,xtr,xbl,xbr) {
var str = "";
var xleft = xtr;
var xright = xtl;
var yh = yt-yb;
var sloperight = (xtr-xbr)/yh;
var slopeleft = (xbl-xtl)/yh;
var flag = true;
var leftdiff = xtr - xtl;
var rightdiff = xtl - xtr;
var tmp = [ [xtl, yt], [xtr, yt], [xbr,yb], [xbl,yb], [xtl,yt] ];
// convertMercator2LLAndDraw(tmp, '#ff0', 2);
function pointInTrapezoid(x,y) {
var xsloperight = xbr + sloperight * (y-yb);
var xslopeleft = xbl - slopeleft * (y-yb);
if((x - xsloperight) > rightdiff) {
rightdiff = x - xsloperight;
xright = x;
}
if((x - xslopeleft) < leftdiff) {
leftdiff = x - xslopeleft;
xleft = x;
}
if( (y<yb) || (y > yt) ) {
console.log("y issue");
}
else if(xsloperight < x) {
console.log("sloperight");
}
else if(xslopeleft > x) {
console.log("slopeleft");
}
else return(true);
return(false);
}
for(var i=0;i<points.length;i++) {
if(pointInTrapezoid(points[i][0],points[i][1])) {
str += "1";
}
else {
str += "0";
flag = false;
}
}
if(flag == false) console.log(str);
return({ leftdiff: leftdiff, rightdiff: rightdiff });
}
var viewcnt = 0;
function calculateView(trap, points, center) {
var bbox = getBoundingBox(points);
var bbox_height = Math.abs(bbox[0][1] - bbox[1][1]);
var view = {};
// move the view trapezoid so the path is at the far edge of the view
var viewTop = trap[0][1];
var pointsTop = bbox[1][1];
var yoff = -(viewTop - pointsTop);
var extents = pointsInTrapezoid(points,trap[0][1]+yoff,trap[3][1]+yoff,trap[0][0],trap[1][0],trap[3][0],trap[2][0]);
// center the view trapezoid horizontally around the path
var mid = (extents.leftdiff - extents.rightdiff) / 2;
var trap2 = pointsTranslate(trap,extents.leftdiff-mid,yoff);
view.cx = trap2[5][0];
view.cy = trap2[5][1];
var w = trap[1][0] - trap[0][0];
var h = trap[1][1] - trap[3][1];
// calculate the scale to fit the trapezoid to the path
view.scale = (w-mid*2)/w;
if(bbox_height > h*view.scale) {
// if the path is taller than the trapezoid then we need to make it larger
view.scale = bbox_height / h;
}
view.ranking = view.scale;
var trap3 = pointsScale(trap2,(trap2[0][0]+trap2[1][0])/2,trap2[0][1],view.scale);
w = trap3[1][0] - trap3[0][0];
h = trap3[1][1] - trap3[3][1];
view.cx = trap3[5][0];
view.cy = trap3[5][1];
// if the path is not as tall as the view then we should center it vertically for the best looking result
// this involves both a scale and a translate
if(h > bbox_height) {
var space = h - bbox_height;
var scale_mul = (h+space)/h;
view.scale = scale_mul * view.scale;
cy_offset = space/2;
trap3 = pointsScale(trap3,view.cx,view.cy,scale_mul);
trap3 = pointsTranslate(trap3,0,cy_offset);
view.cy = trap3[5][1];
}
return(view);
}
function thenCalculateOptimalView(path) {
var center = map.getCenter();
var trapezoid = getViewTrapezoid();
var trapezoid_path = convertTrapezoidToPath(trapezoid);
trapezoid_path[5] = [center.lng, center.lat];
var view = {};
//addLayerToMap("start", trapezoid_path, '#00F', 2);
// get the mercator versions of the points so that we can use them for rotations
var m_center = ll2Mercator(center.lng,center.lat);
var m_path = convertLL2Mercator(path);
var m_trapezoid_path = convertLL2Mercator(trapezoid_path);
// try all angles to see which fits best
for(var angle=0;angle<360;angle+=1) {
var m_newpoints = pointsRotate(m_path, m_center[0], m_center[1], angle);
var thisview = calculateView(m_trapezoid_path, m_newpoints, m_center);
if(!view.hasOwnProperty('ranking') || (view.ranking > thisview.ranking)) {
view.scale = thisview.scale;
view.cx = thisview.cx;
view.cy = thisview.cy;
view.angle = angle;
view.ranking = thisview.ranking;
}
}
// need the distance for the (cx, cy) from the current north up position
var cx_offset = view.cx - m_center[0];
var cy_offset = view.cy - m_center[1];
var rotated_offset = pointsRotate([[cx_offset,cy_offset]],0,0,-view.angle);
map.flyTo({ bearing: view.angle, speed:0.00001 });
// once bearing is set, adjust to tightest fit
waitForMapMoveCompletion(function () {
var center2 = map.getCenter();
var m_center2 = ll2Mercator(center2.lng,center2.lat);
m_center2[0] += rotated_offset[0][0];
m_center2[1] += rotated_offset[0][1];
var ll_center2 = Mercator2ll(m_center2[0],m_center2[1]);
map.easeTo({
center:[ll_center2[0],ll_center2[1]],
zoom : map.getZoom() });
console.log("bearing:"+view.angle+ " scale:"+view.scale+" center: ("+ll_center2[0]+","+ll_center2[1]+")");
// draw the tight fitting trapezoid for reference purposes
var m_trapR = pointsRotate(m_trapezoid_path,m_center[0],m_center[1],-view.angle);
var m_trapRS = pointsScale(m_trapR,m_center[0],m_center[1],view.scale);
var m_trapRST = pointsTranslate(m_trapRS,m_center2[0]-m_center[0],m_center2[1]-m_center[1]);
convertMercator2LLAndDraw(m_trapRST,'#f0f',4);
});
}
function waitForMapMoveCompletion(func) {
if(map.isMoving())
setTimeout(function() { waitForMapMoveCompletion(func); },250);
else
func();
}
function thenSetPitch(path,pitch) {
map.flyTo({ pitch:pitch } );
waitForMapMoveCompletion(function() { thenCalculateOptimalView(path); })
}
function displayFittedView(path,pitch) {
var bbox = getBoundingBox(path);
var path_cx = (bbox[0][0]+bbox[1][0])/2;
var path_cy = (bbox[0][1]+bbox[1][1])/2;
// start with a 'north up' view
map = new mapboxgl.Map({
container: 'map',
style: 'mapbox://styles/mapbox/streets-v9',
center: [path_cx, path_cy],
zoom: 12
});
// use the bounding box to get into the right zoom range
map.on('load', function () {
addLayerToMap("path",path,'#888',8);
map.fitBounds(bbox);
waitForMapMoveCompletion(function() { thenSetPitch(path,pitch); });
});
}
window.onload = function(e) {
displayFittedView(myPath,60);
}
body { margin:0; padding:0; }
#map { position:absolute; top:0; bottom:0; width:100%; }
<script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.37.0/mapbox-gl.js'></script>
<link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.37.0/mapbox-gl.css' rel='stylesheet' />
<div id='map'></div>
Smallest surrounding rectangle would be specific to pitch=0 (looking directly down).
One option is to continue with smallest surrounding rectangle approach and calculate the transformation of the target area - just like a 3d engine does. If this is what you do maybe skim through unity docs to better understand the mechanics of viewing frustum
I feel this wouldn't be appropriate for your problem though as you'd have to re-calculate a 2d rendering of the target area from different angles, a relatively expensive brute force.
Another way to normalize the calculation would be to render a viewport projection into target area plane. See for yourself:
Then all you have to do is "just" figure out the largest size your original convex hull can fit into a trapezoid of that shape (specifically a convex isosceles trapezoid since we don't manipulate camera roll).
This is where I get a little out of depth and don't know where to point you for a calculation. I figure it's at least cheaper to iterate over possible solutions in this 2D space though.
P.S: One more thing to keep in mind is the viewport projection shape will be different depending on FOV (field of view).
This changes when you resize the browser viewport, but the property doesn't seem to be exposed in mapbox-gl-js.
Edit:
After some thought I feel the best mathematical solution can feel a little "dry" in reality. Not being across the use case and, possibly, making some wrong assumptions, I'd ask these questions:
For a route that's roughly a straight line, would it always be panned in so the ends are at bottom left and top right corners? That would be close to "optimal" but could get... boring.
Would you want to keep more of the path closer to the viewport? You can lose route detail if a large portion of it is far away from the viewport.
Would you pick points of interest to focus on? Those could be closer to the viewport.
Perhaps it would be handy to classify different types of routes by shape of hull and create panning presets?
Hopefully this can point you in the right direction with some tweaking.
First I set up the two points we want to show
let pointA = [-70, 43]
let pointB = [-83, 32]
Then I found the middle of those two points. I made my own function for this, but it looks like turf can do this.
function middleCoord(a, b){
let x = (a - b)/2
return _.min([a, b]) + x
}
let center = [middleCoord(pointA[0], pointB[0]), middleCoord(pointA[1], pointB[1])]
I used turfs bearing function to have the view from the 2nd point look at the first point
let p1 = turf.point(pointA)
let p2 = turf.point(pointB)
let points = turf.featureCollection([p1, p2])
let bearing = turf.bearing(p2, p1)
Then I call the map and run the fitBounds function:
var map = new mapboxgl.Map({
container: 'map', // container id
style: 'mapbox://styles/mapbox/outdoors-v10', //hosted style id
center: center, // starting position
zoom: 4, // starting zoom
pitch: 60,
bearing: bearing
})
map.fitBounds([pointA, pointB], {padding: 0, offset: 0})
Here's a codepen: https://codepen.io/thejoshderocher/pen/BRYGXq
To adjust the bearing to best use the screen size is to get the size of the window and adjust the bearing to take the most advantage of the available screen space. If it's a mobile screen in portrait, this bearing work perfect. If you are on a desktop with a wide view you will need to rotate so point A is in one of the top corners.
I am rendering a raster map using d3.geo.tile, like in this example here (the raster images don't work on that page, so I cloned it over here). Unlike this example I have thousands of points to show, so I am rendering them using HTML5 Canvas instead of SVG. I positioned the canvas directly over the map.
The points are rendering correctly, and I am able to pan the map. However, if I zoom in the points are not translated to the proper coordinates.
Here is the function that draws these points:
function set_scales() {
var translate = zoom.sub_regions.translate(),
scale = zoom.sub_regions.scale(),
width = sub_region.get('width'),
height = sub_region.get('height');
var x1 = -translate[0]+width/2;
var y1 = -translate[1]+height/2;
var x2 = width + x1;
var y2 = height + y1;
var x = d3.scale.linear().domain([x1, x2]).range([0, width]);
var y = d3.scale.linear().domain([y1, y2]).range([0, height ]);
draw_canvas();
function draw_canvas() {
sub_region.var.context.clearRect(0, 0, width, height);
var data = sub_region.get('points');
if (!data) {
return;
}
var i = -1, n = data.length, d, cx, cy;
var canvas = sub_region.get('context');
canvas.fillStyle = '#0A00FF';
canvas.beginPath();
while (++i < n) {
d = data[i];
cx = x(d[0]);
cy = y(d[1]);
canvas.moveTo(cx, cy);
canvas.arc(cx, cy, 1, 0, 2 * Math.PI);
}
canvas.fill()
}
}
I know that I should be using the scale variable in there somehow, but I can't figure out how. The scale at which the points are positioned properly is 4096. I tried making a variable called zoom_factor setting it to 4096/scale, and multiplying the x1, x2, y1, and y2 coordinates by it, but that didn't work. Perhaps I didn't do it correctly.
I took some screenshots:
This is before the zoom (points render correctly):
This is after the zoom (points translated to incorrect coordinates):
If you want to see it in all its broken glory go here and click on the United States, then select "Stations."
I could really use some help on this one; been running in circles for days!
I'm using d3 tree layout similar to this example: http://bl.ocks.org/mbostock/4339083
I implemented a search box that when typing, centers your screen on a virtual "average" position of all the appropriate nodes.
I want to adjust the scale, so that selected nodes will be
All Visible
As zoomed in as possible.
If the search match is exactly 1, simulate the clicking on the node, else center to this virtual position.
if (matches[0].length === 1) {
click(matches.datum(), 0, 0, false);
}
else {
var position = GetAveragePosition(matches);
centerToPosition(position.x, position.y, 1);
}
This is what the centerToPosition function looks like:
function centerToPosition(x0, y0, newScale) {
if (typeof newScale == "undefined") {
scale = zoomListener.scale();
}
else {
scale = newScale;
}
var x = y0 * -1; //not sure why this is.. but it is
var y = x0 * -1;
x = x * scale + viewerWidth / 2;
y = y * scale + viewerHeight / 2;
d3.select('g').transition()
.duration(duration)
.attr("transform", "translate(" + x + "," + y + ")scale(" + scale + ")");
zoomListener.scale(scale);
zoomListener.translate([x, y]);
}
So how can I calculate the new scale? I tried different variations by taking the extents of the data points
var xExtent = d3.extent(matches.data(), function (d) {
return d.x0;
});
var yExtent = d3.extent(matches.data(), function (d) {
return d.y0;
});
Also tried looking at the transform properties of the group before centering the screen.
var components = d3.transform(svgGroup.attr("transform"));
I'll try to add a js fiddle soon!
EDIT: Here it is: http://jsfiddle.net/7SJqC/
Interesting project.
The method of determining the appropriate scale to fit a collection of points is fairly straightforward, although it took me quite a while to figure out why it wasn't working for me -- I hadn't clued in to the fact that (since you were drawing the tree horizontally) "x" from the tree layout represented vertical position, and "y" represented horizontal position, so I was getting apparently arbitrary results.
With that cleared up, to figure out the zoom you simply need to find the height and width (in data-coordinates) of the area you want to display, and compare that with the height and width of the viewport (or whatever your original max and min dimensions are).
ScaleFactor = oldDomain / newDomain
Generally, you don't want to distort the image with different horizontal and vertical scales, so you figure out the scale factor separately for width and height and take the minimum (so the entire area will fit in the viewport).
You can use the d3 array functions to figure out the extent of positions in each direction, and then find the middle of the extent adding max and min and dividing by two.
var matches = d3.selectAll(".selected");
/*...*/
if ( matches.empty() ) {
centerToPosition(0, 0, 1); //reset
}
else if (matches.size() === 1) {
click(matches.datum(), 0, 0, false);
}
else {
var xExtent = d3.extent(matches.data(), function (d) {
return d.x0;
});
var yExtent = d3.extent(matches.data(), function (d) {
return d.y0;
});
//note: the "x" values are used to set VERTICAL position,
//while the "y" values are setting the HORIZONTAL position
var potentialXZoom = viewerHeight/(xExtent[1] - xExtent[0] + 20);
var potentialYZoom = viewerWidth/(yExtent[1] - yExtent[0] + 150);
//The "20" and "150" are for height and width of the labels
//You could (should) replace with calculated values
//or values stored in variables
centerToPosition( (xExtent[0] + xExtent[1])/2,
(yExtent[0] + yExtent[1])/2,
Math.min(potentialXZoom, potentialYZoom)
);
}
http://jsfiddle.net/7SJqC/2/