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If I drag to change the Alpha value for a material, it updates continuously in the viewport when viewport_shade is set to Material; the object appears to fade in and out.

However, if I use keyframes to change that same value, the display does not update. What's going on? Is this a bug?

Notes:

  • I don't think this is a duplicate of this question because the asker seems to be referring to Rendered mode rather than Material mode. It's a little unclear what mode he was referring to, but there is no useful answer to my question there, and that question is 2 years old.
  • I have enabled Transparency under Display in the object properties.
  • I have set Shading to GLSL.
  • I'm using Blender 2.7.4 on Kubuntu 14.04 64 with a Nvidia GTX 750 Ti.
  • You can replicate this simply by creating a cube, giving it alpha transparency and doing as described above.
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I am fairly certain this is a limitation of the current system. Simply put the changes in material settings don't trigger updates in the viewport. Manually altering values in the node editor or the material properties causes the UI to deliberately send an update event to the viewport, keyframed changes during playback don't. The keyframed changes do pass through to the render engine though.

I wouldn't expect this to change until the new dependency graph work is finished.

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  • $\begingroup$ What a bummer. Could you link to any details (source, discussions, or references) about the dependency graph work you mentioned? $\endgroup$
    – foobarbecue
    Commented Mar 22, 2015 at 14:08
  • $\begingroup$ Also, any workarounds? Is there a way to manually refresh? $\endgroup$
    – foobarbecue
    Commented Mar 22, 2015 at 15:55
  • $\begingroup$ It was working on one of my objects for a while! I pressed play and the opacity changed on one object, but not on the others which were also keyframed. This has got to be the single most serious bug in all of Blender. $\endgroup$
    – foobarbecue
    Commented Mar 22, 2015 at 17:51
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    $\begingroup$ If you want to build your own copy of blender then you can try the depsgraph_refactor branch from blender's git repo (not sure how usable it is now). Aligorith has done a lot of the work and planning and has a written about it. You can also find a few posts with videos at code.blender.org there is also some info at wiki.blender.org $\endgroup$
    – sambler
    Commented Mar 22, 2015 at 22:08
  • $\begingroup$ Thanks for the info. I might try it, but I'm already on the multiview branch because I'm doing stereo 3D. $\endgroup$
    – foobarbecue
    Commented Mar 23, 2015 at 2:33

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