title: renderOrder doesn't work when the scene has transparent objects
body: <p>I want to render a opaque object behind all my transparent objects by setting <code>mesh.renderOrder = 9999</code> as well as <code>material.depthTest = false</code> for all my opaque objects. But the render order seems doesn't work when my scene has transparent objects. My opaque objects get blended with the transparent objects.</p>
  
  <p>It works well when all the objects are opaque. But when I set the material of some of the objects to <code>transparent = true</code>, the render order seems doesn't work.</p>
  
  <p>I've already set <code>renderer.sortObject = true</code>. I don't want to set it to <code>false</code> because I can't control the order of loading my objects.</p>
  
  <p>Is there any way to render opaque objects after transparent objects?</p>