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Maniphest T44518

Weak Reflections of Volume Scatter Anisotropy
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Description

System Information
64bit Manjaro Linux, kernel 3.19
GeForce GTX 650 Ti Boost, driver 346.59

Blender Version
Broken: 2.75-dev, hash bdf6393

Short description of error
When the Anisotropy setting is used with the Volume Scatter node, the volume effect appears stronger around light sources, and weaker away from them, resulting in a glare or halo around lamps. However, reflections on glossy surfaces show a much weaker halo/glare effect around reflected lamps, as is visible in the render below.

This occurs with both CPU and GPU mode. OSL mode was not tested, since it appears to mysteriously be unavailable on all official blender builds I have tried.

Exact steps for others to reproduce the error

  1. Download and open the following .blend file:
    VolumeScatterAnisotropy_Reflections.blend141 KBDownload
  2. Render
  3. The glare/halo around the emission mesh will be much smaller on the sphere, much like the render above.

Related Objects

Event Timeline

Zauber Paracelsus (zauberexonar) created this task.Apr 27 2015, 6:07 AM
Zauber Paracelsus (zauberexonar) raised the priority of this task from to 90.
Zauber Paracelsus (zauberexonar) updated the task description. (Show Details)
Zauber Paracelsus (zauberexonar) added a project: BF Blender.
Zauber Paracelsus (zauberexonar) edited a custom field.
Zauber Paracelsus (zauberexonar) added a subscriber: Zauber Paracelsus (zauberexonar).
Thomas Dinges (dingto) added a subscriber: Thomas Dinges (dingto).Apr 27 2015, 4:39 PM

With "official" I assume you mean builds from builder.blender.org? They should all have OSL enabled.

Zauber Paracelsus (zauberexonar) added a comment.Apr 27 2015, 4:41 PM

@Thomas Dinges (dingto): There was no OSL problem. It had simply been a while since I had reason to activate it, and I forgot that it was a checkbox under CPU mode, and mistakenly believed it to be in the device menu dropdown.

Sergey Sharybin (sergey) changed the task status from Unknown Status to Unknown Status.Apr 28 2015, 10:45 AM
Sergey Sharybin (sergey) claimed this task.

I'm not sure why you consider this a bug. Glossy reflection is already reflecting light in direction of camera, meaning increasing world's volume scatter anisotropy just prevents light to scatter "sideways", reducing the halo effect. And at the same time the spherical light source emits light in all directions, so increasing volume anisotropy doesn't affect on it's halo that much.

So thanks for the report, but i don't really see issue so far.

Zauber Paracelsus (zauberexonar) added a comment.Apr 28 2015, 3:22 PM

Okay. I guess I don't really understand what anisotropy does, then.