AMD & Intel speed and lightflickering bug? ...fixed

[under1979]

Hi folks!

I was testing the lastest Vray demo build and i realized of a great difference of rendertime and light flickering between an AMD processor and Intel.

I don´t know if this is a bug or if this is the best place to put this.... anyway:

LIGHTMAP TEST. Intel P4 3.06 Ghz hyperthreading:

www.mirsev.com/stuff/LM_test_Intel.mov





LIGHTMAP TEST. AMD 3000XP Barton

www.mirsev.com/stuff/LM_test_AMD.mov



Of course they have same settings...

Regards,

Jorge.

[egz]

Hi, are you sure the settings are the same? The huge difference in rendertime and quality would suggest that the Intel file has much lower settings. You do know that all settings are reset whenver you save with the demo version?

In my experience there is no noticeable difference between Intel and AMD processors (I render on both every day).

[under1979]

Hi egz,

You do know that all settings are reset whenver you save with the demo version?

Yes, the settings are the same. I have to setup it again everytime i open the file

Anyway here is the file and a screenshot of the settings for anyone who wants to test it.

www.mirsev.com/stuff/LM2_Proof.rar

www.mirsev.com/stuff/LM_Settings.jpg

note also the lightflickering in the Intel version .mov file...

Regards,
Jorge.

[natty]

I render on both everyday aswell and have never once noticed a speed drop between them .. if anything my AMD's are a milli second faster. and as for your light flicker ...well that depends on how you calc your scene.

[egz]

Yes, I noticed the flicker, and I believe this is because the settings are lower on the Intel version. Can't test the scene here right now (all CPUs are at 100% because of a project) but I might get a chance to test it tomorrow.

BTW: Do you have auto-save on, that would probably reset the settings without you knowing...

[natty]

well i rendered your scene and it seems fine... (On an AMD Machine)

[under1979]

Hi,

Sorry ezg and natty it was my fault about rendertime. A little problem with bios setting -in the AMD- Now it renders in the right way Many thanks by the way.

However about lightflickering i think it is not for lower setting -i'm sure are the same- It seems to be a problem of tone mapping...

Regards,

Jorge.

[natty]

hi ..

you have a moving object which will make the light move aswell .. so how did you render the animation irr map ?

[under1979]

Yes, a lightmap and imap per frame.

In the AMD machine light changes gradually and in the Intel doesn't do it as show the 2 animations. It's strange

Regards,
Jorge.

[egz]

Jorge,

I've had a chance to do a quick test, and confirm the problem:
http://www.egz.com/vray/flicker_01.mov

What is interesting is that in my test it is the AMD that flickers, and the Intel is nice and smooth, the opposite of your result. The obvious reason for this is that in your test the Pentium is multithreaded and the AMD single threaded, while in my test it is opposite.

I had a chat with Vlado about this just now, and he told me that the problem is indeed with lightmap and multi threading. The reason is that with a single thread, the lightmap samples always fall in the same place with multiple threads, the samples may change places. This gives you the flickering in animations. The only workarounds are rendering without multithreading, or increasing the lightmap samples, neither of which are ideal solutions. Vlado is working on a fix for this he said, so hopefully this is a temporary issue.

[under1979]

Hi egz. Interesting stuff...

or increasing the lightmap samples

I've tried this but it was more or less the same result...

Vlado is working on a fix for this he said, so hopefully this is a temporary issue.

Great news!

Thanks very much.

Regards,
Jorge.

[egz]

Vlado has fixed the problem for the next build. I just tested the same scene with an internal 1.46.11 build I got this afternoon:
http://www.egz.com/vray/flicker_02.mov

excuse the short clip but I couldn't be bothered to render more than 10 frames

I don't know when the build will be released, so don't ask

[under1979]