Consider I have the following HTML5 path:
var myPath = paper.path([
'M', 0, 0
'L', 100, 100,
'L', 150, 50,
'Z']
]);
myPath.transform(['s', 0.5, 0.5, 0, 0]);
After tranformation (scaling) my path resizes accordingly in half, but inspecting the element is the same path string but with transformation matrix applied. Is there any way to retrieve the pathString resulted (lets say M,0,0,L,50,50,L,75,24,z).
I think you need transformPath method: http://raphaeljs.com/reference.html#Raphael.transformPath
The only solution would be using Raphael 1.x which used to modify paths instead of applying transformations. Otherwise you'd need to write your own routines to convert apply matrix transformations to paths (really difficult).
Please check my answer HERE and the testbed HERE.
There is a function flatten_transformations() which can bake (or apply) transforms to paths, so that transform attribute can be removed. It can handle all path segments (also arcs).
OLD ANSWER (not so complete implementation):
Of course there is a way (example in JSBIN) to get a resulted path data after transformations applied. And even very easy way.
Let's suppose we have a SVG path pathDOM and it's root element svgDOM. We can get a transformation matrix of path's coordinate space to root element's coordinate space using native getTransformToElement() -function. It is used this way:
var matrix = pathDOM.getTransformToElement(svgDOM);
When we apply this matrix to all points in path, we get a new path data, where all coordinates are relative to root element. It can be done this way:
var pt = svgDOM.createSVGPoint();
pt.x = some_x_coordinate_of_path_data;
pt.y = some_y_coordinate_of_path_data;
var new_point = pt.matrixTransform(matrix); // <- matrix object, which we created earlier
var new_x = new_point.x;
var new_y = new_point.y;
And that's it! After conversion the transform attribute can be emptied.
Of course all coordinates in path have to be converted to absolute and eg. Arc segments have to be converted to Line or Cubic Segments, which both can be achieved with Raphaël's path2curve() function.
I made a full functional example of using this "Flattening transformations" functionality in JSBIN. There is a ready made function flatten_transformations(), which is the only one needed (the rest is needed for UI purposes). The example has got a path that is nested inside two g elements. Path has own transformations applied, as well as both g elements. Purpose is to test that also nested transformations are flattened.
The code works in newest main browsers and even in IE9. My code that modifies transformations is rather interesting mix of jQuery, Raphael and native code that it may be cause of some problems in IE9 when clicking buttons, but fortunately those essential native functions getTransformToElement(), createSVGPoint() and matrixTransform() work as expected also in IE. I wanted to test simultaneously how those different coding bases plays together. Because it's the fact that Raphael itself is not perfect enough to handle all possible coding needs (lack of styles and groups and lack of possibility to append svg elements as textual xml-data are just ones to note).
Related
I want two instances of d3.forceCollide(). In one, every node is pushed away from one another to prevent overlap. In the second, only a subset of nodes are pushed away from one another, with a much bigger radius.
To accomplish the second force, I tweak the initialize method to filter the incoming nodes, like so:
function selective(force,filter){
var init = force.initialize;
force.initialize = function(_){return init(_.filter(filter));};
return force;
}
var dpi = 90; // approximate pixels per inch in SVG
var size = dpi * (1/4); // quarter-inch unit size
var universally_applied =
d3.forceCollide()
.radius(size)
.strength(1);
var selectively_applied =
selective(
d3.forceCollide(),
function(d){return d.id === color;}
)
.radius(size*5)
.strength(1);
}
Now, this ALMOST works. I created a fiddle to see it in action: https://jsfiddle.net/jarrowwx/0dax43ue/38/ - every colored circle is supposed to repel every other circle of the same color, from a distance. Every other color, it just bumps into and pushes it out of the way.
If I do not change the order in which things are defined, then the selectively applied force is ONLY applied to the first color (red). If I shuffle the data array before applying forces, it is difficult to define exactly what happens, but the force is applied to some circles and not most of the others, even among the same color.
Any ideas what is going on here, or how to fix it?
The D3 team decided that this behavior was a bug (Isolating forces to a subset of nodes? #72), and fixed it. The fix was included in version 1.0.4 of d3-force, which is available as part of the full D3 build as of version 4.4.0.
The problem is resolved using the solution suggested by "Partial forces on nodes in D3.js", and the code works as intended now.
I'm drawing a simple interpolated line using D3.js (output as path). However, I want part of the path to have a dashed stroke if a boolean in a data point is set to true:
Link to image
An easy solution would be to just draw it with <line> segments instead - but that way I lose the interpolation.
Then I found an example from mbostock, showing how to draw a gradient along a interpolated path. I modified it to just draw transparent path fills whenever the boolean was set to true and white fills when false - while my old path is all dashed.
That works (queue the above screenshot) - but by adding around thousand path elements to the DOM contra having only a single path.
It's not desirable with that many DOM elements, especially since I'm going to make more curves and the site needs to be mobile optimized. Am I missing a much simpler solution?
Wouldn't mind a modified version of mbostock's example doing the heavy calculations in advance, as long as the DOM output is simple.
Thanks!
I prepared this example for another SO question. Screenshot is here:
I think you have enough material there to devise a solution that fits your needs.
Take a look also at this page:
SVG Path Styling
You could use stroke-dasharray to add dashes in the stroke of the generated path in the right places. That would entail finding the proper dash lengths. This can be done by calling pathElm.getPathLength() on the path up to the point where you want it to start being dashed, and to where you want it to end.
Let's say path A that is the part that is before the dashes should start. Set the d attribute with that part and call getPathLength() on it. Let's call this length a.
Append the the part of the path that should be dashed to the d attribute, then call getPathLength() again. Let's call this length b.
Create a new path element with the remaining part of the path, then call getPathLength() on that. Let's call this length c.
Construct a stroke-dasharray property string something like this:
var a = getPathLengthA();
var b = getPathLengthB();
var c = getPathLengthC();
var dasharray = a + " ";
for(var usedlen = 0; usedlen < (b-a); ) {
dasharray += "5 10 "; // just whatever dash pattern you need
usedlen += 15; // add the dash pattern length from the line above
}
dasharray += c;
pathElement.style.strokeDasharray = dasharray;
Here's a static example of that.
I'm new to javascript and d3js. I would like a DOM object to trace out a path specified by a parametrized curve (x(t),y(t)). Here is an example of such a parametrization:
var theta = [];
for(var i = 0; i <= N; i++){
theta.push(2*Math.PI*i/N);
}
var points = [];
for(var i = 0; i <= N; i++){
points.push([Math.cos(theta[i]),Math.sin(theta[i])]);
}
The above is the parametrization of a curve -- in this case, also a circle -- and I would like my DOM object to follow the trajectory of this curve. [Aside: is there any better way to define points? It seems ridiculous to run a for loop.]
A crude way to achieve the sort of effect I'm looking for is to run a for loop in the update() part of d3. First, I simply append a circle to the svg variable, so that it need not be linked to any data. It is then selected and updated without required enter/exit.
for (var i = 0; i <= N; i++){
svg.selectAll("circle")
.transition()
.attr("cx",points[i][0]+w/2) // w: width
.attr("cy",points[i][1]+h/2) // h: height
.duration(dt) //
.delay(dt*i);
}
[Aside: I've heard queue() would be better, as opposed to calculating the total delay. Comments?] However, the easing property of the transition makes it run in a choppy fashion. I imagine I could specify no easing, but I'm sure there must be a better way to achieve what I want, which is simply for the initial DOM object (the circle) to move smoothly along a specific trajectory.
In the end, I would want to do this for multiple DOM objects which will eventually be linked to data, each with a specific curve to follow. Any tips on how I would do this?
Thanks in advance for any help, and I will gladly take any advice, including references.
Interesting but not terribly practical approach
The SVG spec actually has a number of animation options, including the ability to move an object along a path. The path is defined in the same form as for a <path> element, so you could use the d3.svg.arc functions to create the path.
Once you have a path defined, it is easy to use d3 to add in the animation:
http://fiddle.jshell.net/RnNsE/1/
although you'll want to read up on SVG animation elements and attributes.
However, there is a limitation to this wonderful animation: poor browser support. So if this is for a website, you're going to need to do the animation with d3 and Javascript.
Production-ready approach
The key to getting d3 to create smooth animations for you is to use a custom "tween" function on a transition.
When you do a transition, d3 initializes a tween function for each change on each element, and starts up timer functions to trigger the updates. At each "tick" of the timer, d3 calls the appropriate "tween" function with the information about how far along the transition it is. So if the tick occurs 500ms into a 2000ms transition, the tween function will given the value 0.25 (assuming a linear easing function, other easing functions complicate the relationship between time elapsed and the expected "distance" along the transition).
Now, for most changes the tween function is fairly straightforward, and d3 will figure one out for you automatically. If you change a "cx" value from 100 to 200, then the tween function is going to return 125 when the transition value 25%, 150 when the transition is 50%, and so on. If you change a "fill" value from red to yellow, it will calculate the numerical values of those colours and convert between them.
The value returned by the tween function at each tick is then used to update the attribute or style of the element. Since the updates happen many times a second, it usually results in a smooth animation. For the simple example of changing the "cx" value of a circle, the circle moves in a straight line from the starting point to the end point.
But you don't want it to move in a straight line. You want it to move in a circle (or along any path you choose). So you're going to need to create a custom function that tells the circle where it should be 25% of the way through the transition, and where it should be 50% through the transition, and so on.
And if you're worried you have to figure that out on your own, never fear. Like so, so much with D3, Mike Bostock has done the hard work for you. But even he didn't have to do the hard hard work. His approach uses two built-in Javascript functions for SVG paths, getTotalLength() and getPointAtLength(). The first tells you the total length of the path, the second gives you the coordinates of the point a certain distance from the start of the path.
With those two values, it is straightforward to figure out the coordinates you should be at if you want to be a certain percent of the way along the path: at 25%, you want to be at path.getPointAtLength(0.25*path.getTotalLength() ).
Here's Mike's function that makes that happen:
// Returns an attrTween for translating along the specified path element.
function translateAlong(path) {
var l = path.getTotalLength();
return function(d, i, a) {
return function(t) {
var p = path.getPointAtLength(t * l);
return "translate(" + p.x + "," + p.y + ")";
};
};
}
A little confusing, no? A function that returns a function that returns a function.
That's because when you specify a "tween" for a transition, what you actually have to specify is a "tween factory" -- the function that will return an appropriate tween function for each element in your selection.
Now, in his example he only has one path and one object moving along it, so those extra layers don't get used. But in the general case, your tween factory function would take the arguments d (the data object for that element in the selection), i (the index of that element) and a (the initial value of the attribute or style that you're changing). With those values, you have to return the custom tween function which take a transition state value t (a number between 0 or 1, or possibly a bit beyond 1 for certain easing functions) and computes the attribute value at that state in the transition.
You'll note that this function returns a translation instruction. That's generally going to be an easier way to move an object around, compared to using cx and cy, since you can specify both horizontal and vertical movement in one transform attribute call, so you only need the one tween function to do both.
Here's my example from above, updated to use a d3 tween to move the circles along the path:
http://fiddle.jshell.net/RnNsE/2/
Key code:
circles.transition().ease("linear")
.duration(5000)
.delay(function(d,i){return i*5000;})
.attrTween("transform", createPathTween);
//creates a tween function to translate an element
//along the path that is a sibling to the element
function createPathTween(d, i, a) {
var path = this.parentNode.getElementsByTagName("path")[0];
//i.e., go from this <circle> -> parent <g> -> array of child <path> elements
-> first (and only) element in that array
var l = path.getTotalLength();
return function(t) {
var p = path.getPointAtLength(t * l);
return "translate(" + p.x + "," + p.y + ")";
};
}
My version strips out the outermost layer of nested functions from Mike's version, but it adds in a bit of Javascript to find the correct <path> element for each circle element.
Note that you need an SVG path element in order to use the getTotalLength() and getPointAtLength() functions; however, this path can be invisible (fill:none; stroke:none; in CSS) if you don't want it to show on the screen. And again, while my path definitions are hard-coded, you could use one of d3's arc or line generators to construct it for you.
And just for fun, here's my example with a different easing function:
http://fiddle.jshell.net/RnNsE/3/
Note that I didn't change anything about the tweening function -- all that's changed is the t values that d3 passes in to that function as the transition progresses.
P.S. Here's another good resource on d3 custom tween functions:
http://blog.safaribooksonline.com/2013/07/11/reusable-d3-js-using-attrtween-transitions-and-mv/
I'm learning D3 and my toy application is a visualizer for a 2-dimensional gravity simulation using Symplectic Velocity Verlet Integration.
I have had quite some success animating and drawing a path using bound structured data, but it seems to me that D3 isn't really designed for attaching data to more than one element. It sort of assumes that for any given data that there is a clear and simple SVG element that should own it, and this is evident in the direct storage of data within the __data__ property inside the DOM.
It's not clear, though, the proper way to represent a datum with more than one SVG element. For instance, I'd really prefer to draw a path and a circle for each planet, the path traces its past position (and can have a bunch of clever line-length and color interpolation applied), and the circle plots its current position.
I can even come up with a few more elements I might want to draw: A vector-arrow for velocity... A vector-arrow for acceleration...
In my case, my master data structure is constructed like this, and is dynamically maintained in this structure:
var data = [];
function makeParticle(x, y, vx, vy) {
// state vector plus goodies
return [
x, y,
vx, vy,
0, 0,
[] // path
];
}
data.push(makeParticle(400, 100, -0.5, 1));
data.push(makeParticle(300, -100, 0.5, 2)); // and so on
Each element of data is a planet, which contains its current state vector (position, velocity, and cached acceleration (needed for the integrator)) as well as its path history which is an array of positions which is kept truncated to some reasonably large length.
Currently I am updating the path history like this:
var paths = d3.select('svg').selectAll("path").data(data);
paths.enter().append('path'); // put cool transitions here
paths.exit().remove();
paths.attr("stroke", "red")
.attr("d", function(d){
return lineDrawer(d[6]);
})
This works fine, each path tracks its own copy of its own planet's path.
It's not immediately clear to me how to extend this elegantly to include my circle at the head of each path. I certainly do not want to duplicate the entire datum into the circle's DOM element (as the path data is simply not necessary for it).
Edit in light of my self-answer:
I am hoping that someone can help to elucidate a way to use "groups" to make data-driven the set of things to draw for each datum. e.g. [position, velocity, force, path] as data where they are visualized using, respectively, a circle, an arrow closed path, an arrow closed path, and an open path. It is also possible that this is completely overthinking it because these properties are sort of fixed.
I guess in the process of thinking the problem through, it's become clear to me that all I have to do is filter out the data, so that I only attach the position state data to selectAll('circle.planet') rather than the full datum value which includes the massive path history array. This way it gets exactly the data it is responsible for displaying.
It seems like I have to do some more reading about subselections (I'm mostly puzzled by why (or if) the subselections are limited to two dimensions of hierarchy), but this seems completely reasonable. It seems logical, if I want to draw 4 items for each datum, I just have to somehow "assign" the correct subsets of my datum's structure to each SVG visualizer element.
I have a set of several shapes each scaled in different rates.
When the set transformed to another point using
set.transform("tp1,p2")
shapes rescale to their normal sizes. For each of the shapes scaled
in different proportions of their original sizes, i can not give a scale
option to set.transform.
How can i preserve scaling of each item in set during transform()?
My question in code:
http://jsfiddle.net/XHr4H/
Raphael's imperfect way of dealing with this is to allow transformation directives to be either prepended to the transform sequence (using "directive...") or appended to the transform sequence (using "...directive"). In your case, the simplest way to achieve the effect you're after is to prepend the relative transform you want in your setTimeout function.
var paper = Raphael("paper", 200, 200);
var s = paper.set(),
r = paper.rect(0,0,30,30).attr({"fill":"green"}).transform("t27,30s0.2"),
r2 = paper.rect(40,0,30,30).attr({"fill":"red"}).transform("t27,30s0.4");
s.push(r,r2);
setTimeout(function(){
s.transform("t100,150..."); // here 'tis
}, 2000);
The transform("t100,150...") essentially inserts the desired translate into the beginning of the transform string for each element in the set. Thus, r's transform evaluates cumulatively to "t127,180s0.2" and r2's becomes "t127,180s0.4".