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Maniphest T41482

Transparent background and volume emission material
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Description

System Information
Win7 x64, 7970 Radeon

Blender Version
Broken: 2.70a # f93bc76

Short description of error

http://i.imgur.com/4fGn9uv.png

Rendered result to the left, preview and expected result to the left.

Independently confirmed by two users in #blender.

Exact steps for others to reproduce the error

Press Ctrl-Z in the 3D view to the right and F12.

(Drag-and drop doesn't work with IceWeasel in this web app, Pale Moon won't do this web-app's CSRF tokens, and Chromium has withered away.) Here is a link to pasteall.org http://www.pasteall.org/blend/31066

Do do it manually, assign Material > Volume > Emission to an object and set Render > Film > Transparent.

Related Objects

Event Timeline

• Tomas (nanicoar) created this task.Aug 18 2014, 9:42 PM
• Tomas (nanicoar) raised the priority of this task from to 90.
• Tomas (nanicoar) updated the task description. (Show Details)
• Tomas (nanicoar) added a project: BF Blender.
• Tomas (nanicoar) edited a custom field.
• Tomas (nanicoar) added a subscriber: • Tomas (nanicoar).
Kévin Dietrich (kevindietrich) added a project: Cycles.Aug 18 2014, 9:51 PM
Kévin Dietrich (kevindietrich) added a subscriber: Kévin Dietrich (kevindietrich).
Kyle Horseman (KHorseman) added a subscriber: Kyle Horseman (KHorseman).Aug 19 2014, 4:53 PM

Here's a simple demo file that was used to confirm this behavior.

VolumeEmissionTransparencyBugTest.blend471 KBDownload

Sergey Sharybin (sergey) changed the task status from Unknown Status to Unknown Status.Aug 20 2014, 10:55 AM
Sergey Sharybin (sergey) claimed this task.

Blender converts images to the straight alpha before displaying them on the screen (because of the way how ogl is set up), which makes it look like there's no color in the transparent area.

Now, in order to see the values you need to composite the render result on something. Easiest way is to use RGB display mode in the image editor which would composite the render onto the black background.

For now it's not considered a bug, it's just how alpha works in blender. Thanks for the report anyway.

Sergey Sharybin (sergey) mentioned this in T45925: Add shader bug alpha.Aug 27 2015, 5:10 PM
Brecht Van Lommel (brecht) mentioned this in T46670: Volume Emission doesn't render when background is transparent.Nov 3 2015, 12:13 AM