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Maniphest T44528

Light Portals have no apparent effect with Branched Path Tracing
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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 4288ab1

Short description of error
I was trying out the new Light Portals feature with a simple scene, and I found that, while it produced differing images with the default Path Tracing integrator, it had no efffect with the Branched Path Tracing integrator, and the two renders with it enabled and disabled were visually identical, but took about 3x longer to render. On the other hand, when Sample All Direct Lights and Sample All Indirect Lights are turned off, it begins to work, but portals instead seem to increase the amount of noise.

So, I'm guessing that either Branched PT is already better at what light portals do, or it simply isn't effective with Branched PT?

Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps
This is the .blend file I used for testing:

SimplePortalsTest.blend96 KBDownload

Related Objects

Event Timeline

Zauber Paracelsus (zauberexonar) created this task.Apr 28 2015, 1:29 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).
Sergey Sharybin (sergey) changed the task status from Unknown Status to Unknown Status.Apr 28 2015, 11:04 AM
Sergey Sharybin (sergey) claimed this task.

It's not about branched/non-branched path tracing, in your portals are used wrong.

  • Portal's size is cricial, it needs to cover whole area from where background light is coming. You've got it default size which is waaaaay to small comparing with the door frame
  • Background light is crucial word here, currently portals does not guide anything apart from light emitted by the background itself. In your setup majority of the light is coming from the sun.

Here's a modified .blend which shows portals in action:

SimplePortalsTest.blend97 KBDownload

Thanks for the report, but further improvements of new features is something what happens naturally and we can't (for some unspeakable reason ;) to have all cases covered with initial commit of some new feature.

Zauber Paracelsus (zauberexonar) added a comment.Apr 28 2015, 3:27 PM

What do you mean default size? I made sure to scale it up because I assumed that was necesary! Even reopening the original file just now, I can see that the area lamp is the correct size (though the viewport has to be set to wireframe in order to see it).

I even downloaded the copy I had uploaded, and it also is the correct size.

Zauber Paracelsus (zauberexonar) added a comment.Apr 28 2015, 3:45 PM

Anyways, feel free to close the report. I had a misunderstanding of what the light portals were used for.