Quirks that slow down vray...

[Neilg]

Odd topic, but bear with me.

Ive been optimising a dusk scene today because as of last night the render times were about an hour and a half a frame. Since turning down light subdivisions, turning some glossy reflections off (just using specular value), lowering the subd's of most, removing a large amount of displacement and replacing it with normal maps... My render times have gone up.

Same IR map, same settings, no new geometry. IR & QMC GI, QMCAA 1,6 with no filter (it would be nice to keep this level of sharpness) and reinhard. A lot of vray lights.

Is it possible that i've lowered/changed a setting somewhere too much and made it go ballistic? I dont know much about how the QMC/noise sampler stuff works but at the moment its the only thing I know least about to pass the blame to.

Even if not, I wouldnt mind knowing if there are combinations of things that dont play well together within vray.

[vlado]

It is possible that since you reduced subdivs for a lot of things, they became noiser and caused the aQMC image sampler to take more samples per pixel. So you have reduced subdivs from the lights, but they were instead moved to the AA in order to keep the specified noise threshold. This causes a whole lot more rays to be traced and also more evaluations for the irradiance map, which are all slow operations.

The more general issue is that there are different combinations of subdivs that ultimately produce similar visual results but for different render times; however some of them work better than others depending on the scene and there is no exact rule to determine which will be better in advance, without making a few tests first. It all depends on what is causing most of the noise in the first place.

I had an idea of a script that would test a few different settings on a small resolution version of the scene to find out the optimal settings but it looked like people were not very happy with the idea

Best regards,
Vlado

[percydaman]

hmm...why would anyone not be happy with that idea? What it something you asked about on the forum?

[vlado]

Yep, I did ask on the forum, but I can't remember what was the title of the thread.

Best regards,
Vlado

[RErender]

I think the response was generally positive, get to work.

http://www.chaosgroup.com/forum/phpB...ic.php?t=14164

[vlado]

Hmm, it has stuck in my head as being either neutral or generally negative

Best regards,
Vlado

[percydaman]

wow I got from that thread that 90% thought it was a great idea, and 10% thought it would give 'vray newbies' the ability to get good quality renders without the long nights of studying arcane render terminologies and settings. As vray gets more control and hence more complicated, the idea of a 'wizard' that would help optimize some of the less 'obvious' settings would seem a smashing idea!

[sv]

i think i remember this, and i think it's a great idea.
after using lele's exposimeter, anything that will automatically adjust your render to look right seems like a winner to me!

especially if it's an optimisation script from the writers of the beast!

[RErender]

There were a few (about 5-10%) that were worried that it would give the competition a leg up, not a very valid argument as all it is really doing is optimizing the render time (one or two of the dissenters were won over midway through), another small contingent were thrown by the word "wizard" having been burned by bad ones in the past. So yeah mostly positive.

(btw was typing same time as percy)

I'm sure the conversation will take off again it will be fun to see what people feel now. I am all for it!

[DaForce]

Yep +1

Sounds like a good idea

[Da_elf]

i think it should be made available in the download section for owners of vray only and not a direct link that "anyone" can download it. plus it should be hidden behind a multiple choice test with questions that only advanced users could answer and not questions from the manual anyone can answer hehehe.

[Neilg]

So you have reduced subdivs from the lights, but they were instead moved to the AA in order to keep the specified noise threshold. This causes a whole lot more rays to be traced and also more evaluations for the irradiance map, which are all slow operations.

This is so grim. Looks like ive got a lot of trial & error work today...

I think by this point i'm obliged to agree with everyone else and nth the script idea.
...What do you think the chances of it being ready this afternoon are?

[vance3d]

if you can write a script that can optimize settings I'm all for it!

V Miller

[andrewjohn81]

I think it's an awesome idea, so long as it's done right.

I don't want a wizard that just goes ahead and changes my settings. What I want is for it to help teach me.
After applying the wizard it should give a results page where I could just accept them if I don't care to learn why the changes are to be made.
I'd like to see each change, why it is recommended to have the change, then have a checkbox (default to be on) that I could choose not to have that particular change if I want.

Some other suggestions wouldn't be possible to fix also, like "hey, don't use an hdri that 6,000 pixels square unless you Really need the detail. You're gonna crash the heck out of your machine." OK, maybe it wouldn't use that verbiage exactly, but that's the general idea. In that case you'd have to fix the problem yourself, by resizing it, saving it, and changing the map. But it would be nice to warn you of the possible mistake.

If that's kind of the way it's done then I am 100% onboard. If it's a quick wizard just to help fix my stuff without telling me why or what it wants to change then I wouldn't really like it.

[beestee]

If it is an optional script, I don't understand how anyone could protest it. I for one would rather spend my time working on the mood of the image rather than searching for the optimal render settings, which is usually what I do anyways at the cost of slightly higher rendertimes.