Light Portals have no apparent effect with Branched Path Tracing #44528

New Issue

Zauber Paracelsus · 2015-04-28T01:29:08+02:00

Zauber Paracelsus commented

2015-04-28 01:29:08 +02:00

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.blend

**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.blend](https://archive.blender.org/developer/F167396/SimplePortalsTest.blend)

Zauber Paracelsus commented

2015-04-28 01:29:08 +02:00

Changed status to: 'Open'

Zauber Paracelsus commented

2015-04-28 01:29:08 +02:00

Added subscriber: @ZauberParacelsus

Sergey Sharybin commented

2015-04-28 11:04:29 +02:00

Changed status from 'Open' to: 'Archived'

Sergey Sharybin closed this issue

2015-04-28 11:04:29 +02:00

Sergey Sharybin self-assigned this 2015-04-28 11:04:29 +02:00

Sergey Sharybin commented

2015-04-28 11:04:29 +02:00

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.blend

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.

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.blend](https://archive.blender.org/developer/F167590/SimplePortalsTest.blend) 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 commented

2015-04-28 15:27:43 +02:00

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.

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). ![SimplePortalTest_Wireframe.png](https://archive.blender.org/developer/F167640/SimplePortalTest_Wireframe.png) I even downloaded the copy I had uploaded, and it also is the correct size.

Zauber Paracelsus commented

2015-04-28 15:45:12 +02:00

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

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Light Portals have no apparent effect with Branched Path Tracing #44528