Animation - Small Objects/Details flashing

[Matt Sugden]

hi I have an issue with an animation I am currently working on, and in truth I have always suffered this problem with my animations in V-Ray.

 

Small details, usually in the distance are intermittently flashing from frame to frame. I looked into the issue before and I remember having to set the normals tick box, which helped a little but the issue is still there, and still annoying me.

 

I assume this must be a an antialiasing issue?

 

I'm currently using Mitchell-Netravali, set to the default settings, in conjuction with

Adaptive subdivision, set to min -1 /max 2, rand ticked, normals ticked 0.05, and a threshold of 0.1

 

Obviously testing these setting is extremely time consuming, i.e. 24 for an animation of 200 frames, so I wonder if anyone could advise me on a possible tweak or better solution.

 

Oh by the way, I don't think it is an irradiance map issue as I currently using the high setting for the calc.

 

Thanks.

[Matt Sugden]

I've attached a couple of frames to highlight the problem. If you look at the glass partition in the center of the image, just behind and above the foot of the stiars there is a small recessed light in the ceiling which is appearing and disappearing. Arggh!!!

 

It's much worse in another part of the animation too.

[SandmanNinja]

I read in one of 3DATS books about something similar to this.

 

Something about a small object in the distance background and the object will jump from one pixel to another.

 

I think the solution in the book was to add a slight blur that was dependant on the distance from the camera, but this was for grass.

[Brian Smith]

it could be a few things, but those AA settings certainly arent helping. i suggest never using Adapt Subd for production renders unless you have scene with few small details and one that is predominantly large, smoothly shaded surfaces. your scene might qualify, but if you are rendering blurry materials or an animation, you shouldn't use it. use adapt dmc with a min/max rate of 2/5 or 3/6 and a clr thresh of 0.005.

 

make sure you are using the incremental add to current map mode in irradiance map and fly through in light cache. make sure you follow the proper steps in calculating the animation...there are quite a few. also, you might have to use the video filter to prevent flickering issues unless you render high and convert down (like they do in hollywood). you can try rendering without any aa filter which would shave off a little time in the rendering but this might not prevent the flickering.

[Nic H]

maybe a bit of depth blur as well? in conjunction with a blurring filter and the other suggestions should fix it.

[Matt Sugden]

Hi thanks for the comments. In terms of the irradiance map and lightcache precalcs I know what I'm doing there, and I don't think that is what is causing it, or if it is I can't think why.

 

Depth of field blur, if that is what you mean will cripple me in terms of rendering times I reckon, and same for doing them a higher res and down sampling. So I'll have to rule those out, though I can see how down sampling the resolution might help as my small details will essentially become twice as big for instance.

 

I don't think it is my movie comperssion, as you can see the still frames are the problem and this is before the compression stage.

 

I might have a look into the other AA settings though, the DMC stuff you mentioned, I tend yo always use adaptive, so I guess I may have to stray from my comfort zone a little and see if that helps me.

 

Thanks

[Nic H]

What i meant to say was I wouldnt do dof in the actual render but:

 

Use an ExtraTex element with a falloff map set to distance blend (with the appropriate range entered i.e 0m-30m)

 

Then use this a a blur mask in post - quick and easy, wont add to your render time.

 

Also I cant see many instances ever in detailed arch vis work where you would use adaptive subd, except maybe a white flat room with no detail.

[Matt Sugden]

"Also I cant see many instances ever in detailed arch vis work where you would use adaptive subd, except maybe a white flat room with no detail."

 

That's very interesting as I've used it pretty much exclusively for the last 3 years?!

 

Perhaps I shouldn't be? Maybe this is going to open up a whole new world of quality!!!

 

Actually I think the reason I use it is becuase when I first started banging around with v-ray, to me it seemed quicker with no perceptive difference in quality. I may need to have another look at this now I'm a bit more familiar with the software.

[Brian Smith]

here's a simple but good rule of thumb...use adapt subd with default settings for every and all test renders....use adapt dmc for every and all production renders....do that and you will maximize speed vs quality 95% of the time

[Matt Sugden]

use adapt dmc with a min/max rate of 2/5 or 3/6 and a clr thresh of 0.005.

 

I've had a bit of a play with this today (i'll post the my images and findings in a mo) just wondered, brian, or anyone for that matter,

 

the min/max rates, you have a 2/5, 3/6 why would you suggest upping the mins for instance, than say having a 2/6, is there any reason or benefit?

 

Also out of curiosity, when you guys over compensate with rendering higher resolutions and down sampling, do you generally do it by doubling the res? or is that overkill?

 

Thanks

Edited November 10, 2008 by Bewdy

[Matt Sugden]

Ok, so here are my results. I have to say I'm not convinced yet that the AA settings are going to make any difference.

 

I have three renders here. One is my original Adaptive Subdiv -1,2 Render time12m56sec, the other two are DMC, with a 2/5, and a 3/6 0.005 as sugested. the 2/5 is 12m56sec by coincidence, and 3/6 was a whopping 17m16secs.

 

In truth I don't see any benefit in the 3/6 compared to the Adaptive -1,2. The problems areas of this part of the animation are the grey lip line across the top of the sky light and the thin lines of the glass partitions.

 

So, I wonder if my only other alternative is the whacking up the res solution?

Edited November 10, 2008 by Bewdy

[Brian Smith]

see attached pdf...this explains it pretty good. and remember, that your scene might be a rare exception to the rule that adapt subd almost never works for production. if you start using blurry materials, you can forget about using it and getting good results. also, what looks ok in a rendering might not look good in an animation. you might start seeing flickering once you play the animation with adapt subd.

[Matt Sugden]

hi thanks for that. I've read it, and the theory it makes sense. However continuing on a more practical point of this project I still have a flickering animation!

 

I think for my own sanity I may try re-rendering a test of maybe 30frames using the 2/5 DMC, as I really can't stretch to 17mins a frame after pre calcs, it's just too much, my poor little dual cores will be taking close to 40mins a frame at that rate and my output needs to be practical.

 

Still unsure however why a value of 2/6 isn't used for instance? doesn't that just widen the net a bit?

 

I've tried a higher res version now too, to see if that render time is close to practical and also to see if it makes any difference. At 40mins for a 50% bigger image I'll have to forget that too.

 

I think so far the only potential solution might be to post in some DOF, but that is going to mean me rendering out a lot of frames of z-depth info, plus learning a post package such as combustion to implement it, in a very short space of time. But with the added bonus of being physically more accurate I suppose. i think this appeals to me more.

 

Thanks for the help anyway.

Edited November 10, 2008 by Bewdy

[Brian Smith]

well you still haven't give us much to go from...you haven't posted much in terms of settings. there could be several reasons why this is happening. i just listed the most common.

 

you could type 100 for a max value if you wanted to, but if the clr thresh isn't set low enough, then it won't matter. besides, if you don't see a difference in the 6 and 5, why use the 6. you should always strive for the lowest acceptable values and improve them only if necessary. also, if you're GI settings aren't set properly, the image sampler won't do you much good. it's like asking a skilled carpenter to build a house out of mud.

[Matt Sugden]

Hi sorry if I've got your back up, as it seems I may have, as I am of course extremely grateful for any help which is offered.

 

I think although i may appear to be asking some what simple questions, I do feel that I have good overall general grasp of vray, which is why I am a little perplexed by this problem.

 

I have tried several aliasing settings now, including the ones you suggested Brian, and as we all know it is always a trade off between acceptable quality and acceptable timescales. At the moment, I feel like I am just a little short of the quality I am aiming for, but at the limit of my timescales!

 

I've attached all my settings (though my saved light cache is at 2000) rather than the 500 shown.

[Brian Smith]

this will have to be my last post for a while...falling behind big time.

 

i suggest the following settings...if you want to know why do a search for posts that i've made and look for the appropriate titles

 

Change IRmap to Med Animation

HSph Subdivs = 20

Int Samples increase up to 100 (if noise appears because of previous lowering HSph Subdivs)

Make sure you rendered Incremental Add to Current Map

Change Noise thresh to 0.01

Adapt Amount to 1.0

Enable 'Use Light Cache for Glossy Rays'

Get rid of Mitchel AA...can't use that for almost animations...use Video filter or no filter at all

 

Of course there are other areas that can be problematic...such as material settings

[drew_almighty]

Interestingly enough, here is what the visualization insider from 3DAS and CGarchitect has to say:

 

"While using a filter such as Catmull-Rom or Mitchell-Netravali works great for stills, these filter types are sure to maximize the effects of flickering and texture crawling. When you create animations, you must use other filters that blur the rendered output, thereby minimizing these effects. Two such filters are the default Area filter and the Video filter. Remember however that the more blurred a filter, the greater the rendering time. At 3DAS, we try to use the Area filter to create animations (whenever possible) because using the Video filter can easily add 25% to your final rendering times. However, if the Area filter causes too much flickering or texture crawling, we must either use the slower (and more blurry) Video filter or render at a higher output.

 

source:

http://www.cgarchitect.com/upclose/VI/Week6/Antialiasing%20and%20its%20Side%20Effects.pdf

Edited November 11, 2008 by drew_almighty
adding hyperlink

[Matt Sugden]

yep, thanks. I'm using area set 1.3, seeing how that works out.

 

Brian you're settings seem to have sped up my renderings by a reasonable amount, so thanks for that, even with a 3/6 and noise threshold of 0.005. I'm very interested to see the results in the next 14 hours or so!

 

I've also done a few slight tweaks to the model, as some of the problem areas are where the edges of the glass partitions were next to the walls, and next to each other. So I've made these gaps ever so slightly bigger. Hopefully this will give vray ray some room to breath and work it's magic!!

 

I've also selected outline object, as i read somewhere that can sometimes help matters, we'll see.

 

The lights however, I'll just have to wait and see what happens with their flashiness.

[Brian Smith]

i really do hate pushing my own products like this, but i do recommend the vray videos i made last year....if not the full 8 hours, then the condensed 3 hour ones

 

in case your interested

 

http://3dats.vismasters.com/static/training/vray/video

 

http://3dats.vismasters.com/catalog/viewproduct.aspx?product=4503

[Matt Sugden]

Brian, a big thank you for that feedback. the animation looks a lot better and i have learnt a lot from those settings you suggested.

 

The one section I have re-rendered looks a lot better, just need to redo 4 other bits now! Will post the finished animation in WIP when I'm done, along with my final setting in case anyone comes across this thread in the future with a similar problem.

 

Cheers