title: RGraph gradient applied to the single circle
body: <p>I am using the RGraph and I need to create circles with a gradients,
  so they look to be 3D spheres.
  I have created a new node type called blob and I have implemented the
  code as follows. However, the gradient is applied to the entire
  canvas.
  Not sure I could explain it, but is there anyone that can help?</p>
  
  <pre><code>$jit.RGraph.Plot.NodeTypes.implement({
  'blob': {
      render: function (node, canvas) {
          var pos = node.pos.getc(true),
          dim = node.getData("dim");
  
          // not sure about this code
          var ctx = canvas.getCtx();
          var radgrad = ctx.createRadialGradient(0, 0, dim, 0, 0, node.getPos().rho);
          radgrad.addColorStop(0, '#A7D30C');
          radgrad.addColorStop(0.9, '#019F62');
          radgrad.addColorStop(1, 'rgba(1,159,98,0)');
          ctx.fillStyle = radgrad;
  
          this.nodeHelper.circle.render("fill", pos, dim, canvas)
      },
      contains: function (node, canvas) {
          var pos = node.pos.getc(true),
          dim = node.getData("dim");
          return this.nodeHelper.circle.contains(pos, canvas, dim)
      }
  }
  
  });
  </code></pre>
  
  <p>Many thanks</p>
  
  <p>Ivan </p>