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javascripthtmlsvgcoordinateszooming

Animating attribute values with JavaScript | Zooming in the SVG viewBox

We have a SVG grid generated with JavaScript.

The goal is to 2X zoom the SVG grid when the user double clicks on any coordinate on the grid and have a short animation transition between the previous zoom state and current zoom state. This actually works almost 100% fine in my snippet below except one problem:

I can animate the level of zoom but cannot smoothly animate the X and Y coordinate transitions well.

View the snippet below ( preferably in full screen ) and double click on the grid a few times.

'use strict'
function zoom( evt ){
  var loc = getCoords( evt ),
      newX = loc.x / 0.8 - 12.5,
      newY = loc.y / 0.8 - 12.5,
      grid = document.getElementById( 'grid' ),
      viewBoxAttr = grid.getAttribute( 'viewBox' ),
      viewBoxAry = viewBoxAttr.split( ' ' ),
      curX = viewBoxAry[ 0 ], curY = viewBoxAry[ 1 ],
      curZm = viewBoxAry[ 2 ], dblZm = curZm / 2,
      tweenZm = curZm, diffX = 0,
      interval = setInterval( 
        function(){
          if( tweenZm >= dblZm ){
            tweenZm = tweenZm / 1.015625;
            diffX = newX - curX;
          }
          else {
            clearInterval( interval );
          }
          zmOnPt( newX, newY, tweenZm );
        },
        10
      ),
      ary = [];
  
  ary.push( curZm );
  ary.push( dblZm );
}

var grid = document.getElementById( 'grid' );
grid.addEventListener( 'dblclick', zoom );

createLines( '.h-lns' ); createLines( '.v-lns' );
createLabels( '.h-num' ); createLabels( '.v-num' );
recalibrate();
<head>
  <link id="main" rel="stylesheet" 
         href="https://codepen.io/basement/pen/brJLLZ.css"
  >
  <link id="animations" rel="stylesheet"
        href="https://codepen.io/basement/pen/zdXRWo.css"
  >
</head>
<body id="body">
  <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" class="cntr" id="grid">
    <script id="injectGrid" xlink:href="https://codepen.io/basement/pen/brJLLZ.js">
    </script> 
    <g id="drawing">  
      <circle cx="60" cy="40" r="0.5" fill="#0dd" opacity="0.9" />
      <circle cx="70" cy="40" r="0.5" fill="#0dd" opacity="0.9" />
      <path
        fill="none" opacity="0.5" stroke="#0dd" stroke-width="0.5"
        d="
          M60, 40
          A10, 10
           0,
           0, 1
           70, 50
          C70, 55
           65, 60
           60, 60
          Q50, 60
           50, 50
          T55, 35
          T70, 40
        "
      />      
    </g>
  </svg>
  <script id="sidebar" src="https://codepen.io/basement/pen/zdXRWo.js"></script>
  <script id="main" src="https://codepen.io/basement/pen/yorjXq.js"></script>
</body>

Notice the smooth zoom animation coupled with the jarring x and y translation? The viewBox just skips to the X and Y coordinate you clicked without animating over to it. Then it zooms in on the now centered coordinates.

The goal is for the x and y to transition smoothly with the zoom.

I've hidden a lot of the code I think is irrelevant in separate files this snippet links to on codepen. If you want to see those without copy and pasting the source code though, here is a list:

MAIN CSS: https://codepen.io/basement/pen/brJLLZ.css

ANIMATION CSS: https://codepen.io/basement/pen/zdXRWo.css

GRID CREATION JS: https://codepen.io/basement/pen/brJLLZ.js

SIDEBAR CODE: https://codepen.io/basement/pen/zdXRWo.js

MAIN JAVASCRIPT: https://codepen.io/basement/pen/yorjXq.js

Solution

  • Your zoom function seems unnecessarily complicated. It has seemingly arbitrary equation constants that I don't understand, and you are manipulating coordinates in a way that I don't see a purpose for.

    For the version below, I am just halving the viewBox width and height, then centering that on the coordinates where you click the mouse. Then, for the animation, I just do a linear interpolation from the old viewBox values to the new ones.

    function zoom( evt ) {
  var loc = getCoords( evt ),
      grid = document.getElementById( 'grid' ),
      viewBoxAttr = grid.getAttribute( 'viewBox' ),
      viewBoxAry = viewBoxAttr.split(' ');
  var oldX = parseFloat(viewBoxAry[0]);
  var oldY = parseFloat(viewBoxAry[1]);
  var oldWidth = parseFloat(viewBoxAry[2]);
  var oldHeight = parseFloat(viewBoxAry[3]);
  var newWidth = oldWidth / 2;  // Halving the view width => zoom X2
  var newHeight = oldHeight / 2;
  var newX = loc.x - newWidth / 2;
  var newY = loc.y - newHeight / 2;
  var animProgress = 0;  // Goes from 0 to 1
  var animStep = 0.02;   // Change in animProgress per interval function invocation.

  var interval = setInterval( function() {
    animProgress += animStep;
    if (animProgress > 1)
      animProgress = 1;
    // Calculate a new viewBox corresponding to our animation progress
    var nextViewBox = [
      oldX + animProgress * (newX - oldX),
      oldY + animProgress * (newY - oldY),
      oldWidth + animProgress * (newWidth - oldWidth),
      oldHeight + animProgress * (newHeight - oldHeight)
    ];
    grid.setAttribute("viewBox", nextViewBox.join(' '));
    if (animProgress >= 1)
      clearInterval( interval );
  }, 10);
}


    'use strict'
function zoom( evt ) {
  var loc = getCoords( evt ),
      grid = document.getElementById( 'grid' ),
      viewBoxAttr = grid.getAttribute( 'viewBox' ),
      viewBoxAry = viewBoxAttr.split(' ');
  var oldX = parseFloat(viewBoxAry[0]);
  var oldY = parseFloat(viewBoxAry[1]);
  var oldWidth = parseFloat(viewBoxAry[2]);
  var oldHeight = parseFloat(viewBoxAry[3]);
  var newWidth = oldWidth / 2;
  var newHeight = oldHeight / 2;
  var newX = loc.x - newWidth / 2;
  var newY = loc.y - newHeight / 2;
  var animProgress = 0;  // Goes from 0 to 1
  var animStep = 0.02;   // Change in animProgress per interval function invocation.
  
  var interval = setInterval( function() {
    animProgress += animStep;
    if (animProgress > 1)
      animProgress = 1;
    // Calculate a new viewBox corresponding to our animation progress
    var nextViewBox = [
      oldX + animProgress * (newX - oldX),
      oldY + animProgress * (newY - oldY),
      oldWidth + animProgress * (newWidth - oldWidth),
      oldHeight + animProgress * (newHeight - oldHeight)
    ];
    grid.setAttribute("viewBox", nextViewBox.join(' '));
    if (animProgress >= 1)
      clearInterval( interval );
  }, 10);
}

var grid = document.getElementById( 'grid' );
grid.addEventListener( 'dblclick', zoom );

createLines( '.h-lns' ); createLines( '.v-lns' );
createLabels( '.h-num' ); createLabels( '.v-num' );
recalibrate();
    <head>
  <link id="main" rel="stylesheet" 
         href="https://codepen.io/basement/pen/brJLLZ.css"
  >
  <link id="animations" rel="stylesheet"
        href="https://codepen.io/basement/pen/zdXRWo.css"
  >
</head>
<body id="body">
  <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" class="cntr" id="grid">
    <script id="injectGrid" xlink:href="https://codepen.io/basement/pen/brJLLZ.js">
    </script> 
    <g id="drawing">  
      <circle cx="60" cy="40" r="0.5" fill="#0dd" opacity="0.9" />
      <circle cx="70" cy="40" r="0.5" fill="#0dd" opacity="0.9" />
      <path
        fill="none" opacity="0.5" stroke="#0dd" stroke-width="0.5"
        d="
          M60, 40
          A10, 10
           0,
           0, 1
           70, 50
          C70, 55
           65, 60
           60, 60
          Q50, 60
           50, 50
          T55, 35
          T70, 40
        "
      />      
    </g>
  </svg>
  <script id="sidebar" src="https://codepen.io/basement/pen/zdXRWo.js"></script>
  <script id="main" src="https://codepen.io/basement/pen/yorjXq.js"></script>
</body>