Volume Emission Shader renders as transparent when there is nothing behind it!?

Hi there,

In Cycles, set the start-scene cube’s material to be only an Emission shader plugged into the Volume output.

Set the ‘Film’ render setting to be transparent.

Hit render, and nothing appears.

Put something behind it, and you will see the Emission Volume only where the thing behind it is seen through.

Delete the thing behind it, and render with Film>Transparent unticked - you will now see the Emission volumed cube as it should be seen except without a transparent surround.

So my questions are:

Is there a way to have an Emission Volume material just floating in transparent image?

Is this a bug or is there a sensible reason for it?


The closest thing to a solution to this is to plug a Transparent Shader set to just a bit darker than white, into the Surface output. The less white it is the more clear the Emission volume is, but the duller the colours… so any better way, please tell me!

adding a Volume scattering to the emission shader works ok.

But it’s a strange thing as in the viewport it renders as expected. The final render still have the correct high range colors in it, but with Alpha at 0.