title: soft shadow, shadow blur in SceneKit
body: <p>I add one node and try to setting shadow blur with SceneKit</p>
  
  <p>here's my light config, I did try to set shadowRadius</p>
  
  <pre><code>light = [SCNLight light];
  light.type = SCNLightTypeDirectional;
  light.castsShadow = true;
  light.shadowMode = SCNShadowModeForward;
  light.shadowRadius = 5;
  light.shadowMapSize=CGSizeMake(4000, 4000);
  light.orthographicScale=25;
  light.zNear=1;
  light.zFar=1000;
  </code></pre>
  
  <p>but the result is not softer than when I not set <code>shadowRadius</code>
  it' here:
  <a href="https://i.stack.imgur.com/iYNHf.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/iYNHf.jpg" alt="enter image description here"></a></p>
  
  <p>I did try to add samplecount </p>
  
  <pre><code>light = [SCNLight light];
  light.type = SCNLightTypeDirectional;
  light.castsShadow = true;
  light.shadowMode = SCNShadowModeForward;
  light.shadowRadius = 5;
  // add samplecount
  light.shadowSampleCount = 5;
  light.shadowMapSize=CGSizeMake(4000, 4000);
  light.orthographicScale=25;
  light.zNear=1;
  light.zFar=1000;
  </code></pre>
  
  <p>result look like following
  <a href="https://i.stack.imgur.com/IW3k3.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/IW3k3.jpg" alt="enter image description here"></a></p>
  
  <p>shadow seem soft but this shadow start from bottom of the node (z coordinate is 0). I spend a lot of time to set soft shadow only in the edge of node, not from bottom. But no result.</p>
  
  <p>This problem also occurred when add two node cross over(not only node and geometry as SCNFloor)</p>
  
  <p>My problem is how to get shadow blur(soft shadow) with direction light.</p>
  
  <p>any help would be appreciated!</p>