Next Update 1 IPR: Delay when changing Gamma value of VrayHDRI

[kosso_olli]

Hey guys,
I have a problem here: When I am using IPR on CPU in a scene with an HDRI assigned to the domelight, changing the gamma value or the multiplier of that HDRI causes a really long delay of around 10 seconds depending on then size of the HDRI. This only happens the first time, all the changes afterwards are quick. Can this be changed?
Test procedure is simple, make a teapot and a domelight with a big HDRI inside it (has to be around 16000x8000px).

[yavor.rubenov]

Hello,

So far I got the following:

• start IPR with some big HDR file. Gamma is default at 1.0
• change the gamma to some other value - f.e 2.2. As you say I get quite a delay
• change the gamma back to 1.0 - rendering restarts very fast, no delays
• change the gamma to 2.2 - again fast, no delays
• if I change the gamma to some different value though - i get the long delay again

Is it the same for you or after the first change you don't get any delays no matter what value you use?

The initial delay happens because we reread the hdr file and apply the gamma corrections. This happens single threaded (for some reason - probably we could improve on that) and is slow. Then if you go to the old value - we just reuse the old image that we keep in the tiled textures cache and this is fast.

Best regards,
Yavor

[yavor.rubenov]

By the way - a colleague of mine told me of a temporary workaround - if you set Overall multiplier of the VRayHDRI to be something other than 1.0 (for example 0.999) then changing gamma should be much faster.

[kosso_olli]

Hello,

So far I got the following:

• start IPR with some big HDR file. Gamma is default at 1.0
• change the gamma to some other value - f.e 2.2. As you say I get quite a delay
• change the gamma back to 1.0 - rendering restarts very fast, no delays
• change the gamma to 2.2 - again fast, no delays
• if I change the gamma to some different value though - i get the long delay again

Is it the same for you or after the first change you don't get any delays no matter what value you use?

The initial delay happens because we reread the hdr file and apply the gamma corrections. This happens single threaded (for some reason - probably we could improve on that) and is slow. Then if you go to the old value - we just reuse the old image that we keep in the tiled textures cache and this is fast.

Best regards,
Yavor

Yes, the behaviour is as you describe.
Has it always been like that? I think it was different before Next. The workaround is working, which is even more weird...

[vlado]

We changed some of the code for the bitmap reader indeed. There seems to be place for improvement though.

Best regards,
Vlado

[kosso_olli]

Is there a fix for this already? I still can not understand why changing the gamma, overall- or render multiplier forces a reload of the texture. I have an HDRI plugged in there which is 1.5gb, so every time I change any of these values, I have to wait two minutes. No fun!
I mean, it worked fine for years before Update 1...