Light/surface flicker

[ntavian]

Hey forum members
I am trying to do my first VRAY simple camera pan animation , and I seem to be getting a slight flicker on some surfaces and reflections
either caused by some lights, or the HDRI, or maybe just my poor settings.
attached are 2 jpg files showing the light/surface flicker and my vray settings


please help

[joconnell]

Look into using cached GI - there're a few fly through tutorials for vray using the camera path feature which'll stop any flicker if the camera is the only thing moving in the animation!

[tashko.zashev]

Yes, use camera path should help with this. You can check my reply here
http://forums.chaosgroup.com/showthr...o-saved-Irrmap
post #4, where i have described the precalculation procedure. After that just load the resulting .vrmap file and render all frames.

[ntavian]

so I after watching this tutorial online http://www.timsportfolio.co.uk/tutorials/vray-gi/
i created a light cache file and a Irradiance Map file as directed, setup my new animation with these 2 files, and the flicker went away but my rendering got a lot darker
did I miss something? should the lighting setting have to change by using this method?
see images below

[Neilg]

Aside from his settings being a bit strange it shouldnt have an effect on the brightness of the image. (I would use medium IR settings and 80/40 to start - the animation modes aren't for pre calculated static maps)
Have you loaded the irradiance map into the viewer? You should be able to look at it and see if the information is there.

It's hard to say what the issue is without poking around. Something did go wrong somewhere though.

[ntavian]

I opened up both the IR map and LC files and there wasn't anything there
what should be in these files?
BTW, what settings do you think are a bit strange in that tutorial?

[Neilg]

I said in that post - his IRmap preset mode. do not use the animation presets when saving maps like this.

Not sure if it mentions in that tutorial, but you have to render the IRmap on a single machine, and it cant get interrupted. If you pause/resume the rendering when it's half way through then it loses the data from those first frames

An IR map should look something like this -


You can check where there are holes, and see the kind of coverage you have. I rendered this for a still, so you can see if i moved my camera there's a big area of the sofa and behind it which isnt covered by the IRmap - those areas would be dark and blotchy like the result you just got. From the camera view i'm rendering from however this is covered up by other objects.

The way multiframe incremental works is that it does an IRmap for your frame, keep it stored and starts the next (I usually skip every 20-30 frames, the camera still eventually gets enough coverage for the path) and works that out using the information from the previous frame (it fills in the gaps and checks if there's any more detail it can add in areas it's already done so it doesnt do too much extra work - caclulation of the first frame always takes much longer. expect the first frame to take twice as long as any others, if not more)
it then adds the new calculation to the file already created. If the rendering gets restarted it makes a new file - scrubbing any data that was being used to make it faster and losing everything calculated up to that point. that's why this all needs to be done in one shot by a single machine (you can still use DR to spread the load however)

I hope that makes sense. Once you've got a good IRmap (use the viewer to check before sending a render, plus after a while you'll get a feel for what file size to expect by knowing the kind of scene you rendered so you wont even need to check) you can load it and send the full path to all machines on backburner.

[ntavian]

so my LC and IR map maps were completely grey, do you think that is why my renders looked dark?

BTW thanks for all your help

this info is all new but very helpful to me

[Neilg]

how big was the file size? I would assume that something went wrong when creating them, yes.
Do a low resolution still first - save it, check it and load it.
Then do your animation very low res too (so you can do the IR and check it within 20 mins), and once you've got both of those working with no issues set up the high res one for final render. Trying to do something final quality the first time you're doing this process means it's hard to figure out which step falls apart. Slowly increasing the scope will help you get familiar with the process.

Dropping the resolution down to 300x170 and running a test with the aa at 1,1 so it takes seconds per frame is always worth it. It might seem like a waste at first but averaged out you will end up saving so much time in the long run - we used to render paths multiple times before they could be called final, and since adopting this 'test, test and test again' process I very rarely render a path more than once.