title: What is the correct way to map textures onto SCNSphere
body: <p>I want to use this image as a material for a SCKSphere:</p>
  
  <p><img src="https://i.stack.imgur.com/6lOQWm.png" alt="enter image description here"></p>
  
  <p>I can do this as follows:</p>
  
  <pre><code>SCNSphere *sphereGeometry = [SCNSphere sphereWithRadius:5];
  sphereGeometry.firstMaterial.diffuse.contents = [UIImage imageNamed:@"navball.png"];
  </code></pre>
  
  <p>However, when I run the application, the image has been distorted as it is mapped onto the sphere, and the lines that run from the top to the bottom of the sphere are no longer straight:</p>
  
  <p><img src="https://i.stack.imgur.com/XonaZl.png" alt="enter image description here"></p>
  
  <p>Is there any way to ensure that the material is mapped onto the sphere correctly and the lines remain straight?</p>
  
  <p>This image on the left below shows what I was expecting, and the image on the right shows what I'm experiencing - wavy lines when I would expect them to be straight:</p>
  
  <p><img src="https://i.stack.imgur.com/v0tEr.png" alt="enter image description here"></p>