Backdrop image slows down Iray Preview updating considerably in 4.11/4.12

Taoz

Like the title says, if I use a Backdrop image it slows down Iray Preview updating considerably in DS 4.11 and 4.12. In 4.10 it updates equally fast, Backdrop image or not. Can anyone else reproduce this? 

GTX 1070, NVidia driver 430.86

Praxis

Yes:

v4.10.0.123: About 1 second to redraw a test scene, with or without a Backdrop image.

v4.11.0.383: About 1 second to redraw a test scene, without a Backdrop image, about 2 seconds with a Backfrop image.

The test scene has no Instances, but to make sure in both cases: Render Settings > Optimization > Instancing Optimization = Memory

RTX2070, drivers 430.86, Win7

 

Taoz

Thanks. My numbers are quite different though: 1-2 versus 15-20 seconds, which makes it almost impossible to work with the scene.

But I've just found out that it depends a lot on the size of the image - I was using a 4320x3240 jpg. After changing the size to 1707x1280 it goes a lot faster in 4.12, but it's still slower than 4.10 with the big image.

Wonder why 4.10 seems to be immune to the Backdrop image size while if affects 4.11 and later.

Could it be the driver? There is a new one 431.60, but I hesitate trying it as 430.86 works fine.

And I'm on Win 10 btw.