You can also use it for reflections. This image has an invisible sphere for the reflection of the window and door but was rendered over a gray background.  I could have hidden the background to use it in Photoshop. And this works with both render engines.

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Available on Amazon for the Kindle E-Reader Monster of the North and The Shimmering Mage

Today I break my own personal record for the number of days for being alive.
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I use Poser 13 and win 10