When using a principled volume material with low density value, saved image is translucent. #112647

New Issue

Patrick-McBlenderson · 2023-09-21T03:56:29+02:00

2023-09-21 03:56:29 +02:00

System Information
Operating system: macOS-13.0-arm64-arm-64bit 64 Bits
Graphics card: Metal API Apple M1 Pro 1.2

Blender Version
Broken: version: 3.5.0, branch: blender-v3.5-release, commit date: 2023-03-29 02:56, hash: 1be25cfff18b
Worked: (newest version of Blender that worked as expected)

Short description of error

Renders of an object on a transparent background with a Principled Volume Shader with density set to zero appear fine until saved to a file. When saved to a file, they are fully translucent. Raising the density makes them less translucent.

I believe this is the same problem described in https://blenderartists.org/t/png-image-empty-but-render-in-blender-is-ok-help/1339998/26

Exact steps for others to reproduce the error

Add a sphere.
Give it a material with no surface shader, but a Principled Volume volume shader.
Set the density to 0 and the Blackbody Intensity and Temperature relatively high like in the attached screenshot.
Switch to Cycles renderer and check Film > Transparent in Render Properties.
Render the image.
Observe that the object appears opaque on a translucent background in Blender.
Save a PNG with RGBA selected.
- Expected: The PNG will appear like the rendered image does in Blender
- Actual: The PNG is fully translucent

Additional notes

You can save as a RGB (not RGBA) PNG and the object looks as expected.
Increasing Density makes the object more opaque/less translucent, but does not achieve the appearance I want.
The screenshots I attached are from a different scene than the more minimal blender file I attached. But the same ideas apply.

**System Information** Operating system: macOS-13.0-arm64-arm-64bit 64 Bits Graphics card: Metal API Apple M1 Pro 1.2 **Blender Version** Broken: version: 3.5.0, branch: blender-v3.5-release, commit date: 2023-03-29 02:56, hash: `1be25cfff18b` Worked: (newest version of Blender that worked as expected) **Short description of error** Renders of an object on a transparent background with a Principled Volume Shader with density set to zero appear fine until saved to a file. When saved to a file, they are fully translucent. Raising the density makes them less translucent. I believe this is the same problem described in https://blenderartists.org/t/png-image-empty-but-render-in-blender-is-ok-help/1339998/26 **Exact steps for others to reproduce the error** 1. Add a sphere. 2. Give it a material with no surface shader, but a Principled Volume volume shader. 3. Set the density to 0 and the Blackbody Intensity and Temperature relatively high like in the attached screenshot. 4. Switch to Cycles renderer and check Film > Transparent in Render Properties. 5. Render the image. 6. Observe that the object appears opaque on a translucent background in Blender. 7. Save a PNG with RGBA selected. * Expected: The PNG will appear like the rendered image does in Blender * Actual: The PNG is fully translucent Additional notes * You can save as a RGB (not RGBA) PNG and the object looks as expected. * Increasing Density makes the object more opaque/less translucent, but does not achieve the appearance I want. * The screenshots I attached are from a different scene than the more minimal blender file I attached. But the same ideas apply.

Screenshot 2023-09-20 at 6.41.07 PM.png

189 KiB

blank-png-export-minimal-repro.blend

892 KiB

Screenshot 2023-09-20 at 6.35.23 PM.png

799 KiB