Portals ignore environment intensity in RT GPU

[1funk]

It seems portals are ignoring the environment intensity when using RT GPU

1. Load attached scene
2. Start RT CPU and let it render a little, then save to history
3. Start RT GPU and compare

RESULT: RT GPU is much darker, because the portals are not taking environment intensity into account


NOTES:
If you set the environment intensity to 1.0 (it was previously 20.0), then enable the "For RT GPU" environment material (which has the color set to 20,20,20 instead of 1,1,1), you will see the portals render correctly in RT GPU

[Margarita.Stoeva]

Hello

Thank you for reporting this issue and providing the scene and description. I was able to reproduce it and it's now logged in our bug tracking system.

Best regards,
Margarita

[savage309]

Btw, in general it might be good idea to avoid portals, especially when using V-Ray GPU. There is some speedup, but they can cause troubles as well.

Best,
Blago.

[1funk]

Btw, in general it might be good idea to avoid portals, especially when using V-Ray GPU. There is some speedup, but they can cause troubles as well.

Best,
Blago.

So are you saying portals are currently buggy? Will this be fixed?

I tested them in a scene which just used a white environment. They were really helping RT CPU clean up much faster. I can actually see what I'm doing in real time.
Without them, changing materials etc leaves me with a really noisy image, making it difficult to use RT as a real time preview.
It was actually faster to run production renders since they use lightcache, while RT CPU doesnt (it used to in older releases but this was changed for some reason).

[savage309]

The portals implementation between CPU and GPU is very different, so the lighting result might be different. We don't plan to unify that (that's why I suggested not using them for V-Ray GPU).
We are thinking in a ways to make the portals not needed at all. The reason I suggested not using them for V-Ray GPU is that the GPU render should be fast enough to work without them even now.

Best,
Blago.

[1funk]

The reason I suggested not using them for V-Ray GPU is that the GPU render should be fast enough to work without them even now.

OK thanks for the info Blago. I just did a comparison in my test scene. When I have no portals, RT GPU has some "black" areas which don't appear to get sampled for about a minute. With portals enabled, the entire image can be seen in less than 20 seconds.

So at least on my hardware and this scene, portals seem to help quite a bit for "interactive" changes, while I'm working on the scene

It would be great if I didn't need to use them at all though

[vladimir.nedev]

RESULT: RT GPU is much darker, because the portals are not taking environment intensity into account

I don't think the issue is related to portals.
The environment intensity just didn't work on GPU.
I've merged the fix for this and the issue should be resolved for today's nightly build ( 2018.02.16 ).

Greetings,
Vladimir Nedev

[1funk]

Thanks Vladimir