**System Information**
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 1060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 446.14
**Blender Version**
Broken: version: 2.83.1, branch: master, commit date: 2020-06-25 09:47, hash: `rB8289fc688b3e`
Worked: (newest version of Blender that worked as expected)
**Short description of error**
[Blender does not save the alpha channel correctly for volumetric flames / fire with no smoke, if 'density' is set to zero or less in the 'Principled Volume' shader node.]
**Exact steps for others to reproduce the error**
[load the attached blend and try to get a correct alpha channel saved, I've tried saving as EXR, Targa, DPX and TIFF {all 16bit RGBA), all the files show the flames in the, but only the plane object shows at all in the alpha.
If you set 'density' above zero in the 'Principled Volume' shader, despite fixing the render preview issue ( T52680 -sort of), as in you can see the flames slightly in the render-preview window now, you still get zero or black in the alpha channel in any saved files.
This is what I'm seeing in the compositor-
{F8661768}
Just to be clear: I'm not talking about the render preview issue T52680, with not showing the flames/fire at all as you watch the render.
I'm saying I'm not getting the alpha channel for the flames, that should be generated from what I can actually 'see' in the viewport, as in the rendered camera view in the GUI.
Surely if it shows in the GUI-viewport correctly, it should be able to save a valid alpha for that image? I mean if you can't trust that you can get what you create in the GUI-viewport out of the software that's quite a fundamental one isn't it?
]
[Based on the default startup or an attached .blend file (as simple as possible)]
{F8661725}
and here's the VDB frame in case it didn't pack-
{F8661750}