How to tune render times - bsp / memory / quasi mc?

[joconnell]

Hi Folks,

I'm working on a load of film res ads in 1.46.10 at the moment which is render with motion blur, geometry shag hair and GI - The render times at 2k are around 2 hours on dual machines with 2 gigs of ram using static memory assignment. It's using quasi monte carlo for the GI, 3d motion blur and the scene has hair fx in geometry mode. I've never tuned vray renders before so aside from lowering the face coefficient and playing with subdivs I don't know what makes the greatest difference to rendering time - I'm thinking of switching the GI method to irradiance maps but I'm wondering what will make the biggest difference to the likes of motion blur and overall sampling?

Bit of a short deadline and running out of render time

[dbuchhofer]

the overall biggest difference will be in the qmc sampler rollout .. its how you can control your 'acceptable' noise amount, you can lower the qualities a fair amount on some scenes without too much of a visual problem.. your best bet is to check out the manual at your vray login page, and look at the examples / qmc.. and also at the examples gi types..

Qmc gi is basically just 'brute force' it has its advantage in that there isn't any worrys about blinking differences in gi between frames, so you can theoretically use a fairly low solution quality. but its slow as sin for many types of scenes someone else'll have to speak up on gi speeds with blurrys

(I've never had to deal with that many blurry effects at once being a lowly arch artist, so mabye someone else will chime in..) but word is from viewing around the forums for the last couple years that the 'simpler' AA types might speed you up some, using either the QMC AA type, or even fixed rate.. with the thoughts that a fixed rate of 4, is about the same as an adaptive of 0-2 if the adaptive has to forgo undersampling

[joconnell]

Cheers for the heads up on that - I think we've got the image quality we need so I reckon I'll start digging in to the raycaster and probably turn down the qmc when the director isn't looking

Is there anything useful in the vray logging window I can keep an eye on to give me some hints or just go with the end render time?

[Trapezium]

I agree about the AA, I've found that Adaptive QMC sampling speeds up rendering of fine details like hair rather than Adaptive subdivisions.

--Jon

[joconnell]

Yeah, we're using adaptive qmc at 1,4 in this case - i heard that it's better with blurry effects like moblur and dof which we're using. I'd really like to try 1.46.12 as it seems a lot lighter on memory and would probably give us less crashes but I'm kinda scared to change anything in case it fucks a load of stuff up and I lose more time :/