Frosted Glass for Animation

[jujubee]

I have an upcoming animation deadline. I need a white frosted glass that wont flicker with much visible noise.

Currently, I use a glass that is very low subdivision in the refraction channel of a vraymaterial - the low subs is how I get the frosted effect. Will this cause flickering noise as I go to animate?

[MoonDoggie]

Maybe render out a test with like 30 frames?

[DanielBrew]

It shouldn't flicker if you keep 'time independent' checked in the DMC sampler.

Dan

[instinct]

Wich on the other hand creates non-moving noise patterns that seem to crawl over the surface. And i am pretty sure it will flicker the heck outta itself :P

Kind Regards,
Thorsten

[^Lele^]

Low subdivisions not flickering is like the sun shining at the equator not being hot.
The look of a low-subdivs glossy refraction is similar, but definitely not the same as a high subdivs one with some fine bumpmapping on.
There's no other trick i know of than to have the frosted glass look clean in the still, before moving on to the animated bit, and even that, depending o the camera move, may need upping the quality.
Comfort yourself by knowing it will be on a per-material basis, and not an overall setting.

[dbuchhofer]

Depending on the exentiveness of that material, i tend to just do it as a seperate alpha, and add a little blur to it in post not the most beautiful way, but it works generally as a very fast-for-rendering alternative to the extra high subdivs

[DanielBrew]

Wich on the other hand creates non-moving noise patterns that seem to crawl over the surface. And i am pretty sure it will flicker the heck outta itself :P

You are right about the crawling, I thought the noise stayed static relative to the object but it doesn't, it stays static relative to the frame. Bit like a dirty lens. It doesn't flicker though

Dan

[jujubee]

Depending on the exentiveness of that material, i tend to just do it as a seperate alpha, and add a little blur to it in post not the most beautiful way, but it works generally as a very fast-for-rendering alternative to the extra high subdivs

Awesome guys - Dave I'll give that a shot. Save out to Alpha (or MtlID) then pop into AE? Should be an amazing time-saver.

[flyinhawaiian]

Another suggestion...

Another desperation move (that I've had to do in the past on tight deadlines) is to render a quick, high-res, head-on view of the object and then remap that rendered image right back onto the object with 100% self illumination. It's kind of like using planes with pictures of trees mapped onto them instead of real 3d trees, but for certain moves, and under certain deadlines, it works. Good luck!

Aloha,
Joel

[jujubee]

The last move is a bit tricky...

[^Lele^]

I thought you didn't ask for compositing tricks, rather for a non-flickering, and similar look to, your low subdivs frosted glass - in camera -.
Pushing it further into compositing and matte painting sure opens up possibilities, but is it really a time saver?
How much time is spent to learn/apply such techniques, rather than upping subdivs in the material and render out with the knowledge it'll work?
Unless you're having that glass covering the whole image, the impact can't be that hard.
my 2c

[tammo]

you can turn off glossy, set diffuse color to white and make it slightly transparent.

[^Lele^]

Just to show what i mean, and what i understood was the problem:

Respectively, the thumbnails show:
frosted glass look, 8 subdivs,
same glass, 24 subdivs, just looks smoother,
same glass, 24 subdivs, very fine noise in the bump channell.

The latter requires more samples, but being the visible noise a bumpmap, it will remain steadily on the object, rather than flicker.
It may not be obvious due to the compression of the jpgs, but give it a try and see for yourself.

[jujubee]

Hmm. Thanks. The second image I think works perfectly actually.

What do you think is the best Global subdivisions settings for materials to ensure a rendering will not flicker? Around 14? This will only be 720x480 - and yes, there are large panes of frosted glass throughout the rendering.

[^Lele^]

Generally as low as you're comfortable with, especially when large amounts of the screen are covered with the effect.
24 is possibly overkill, maybe 14 works well enough.
As said by moondoggie, it's likely easier if you do a simple 3 frame preview of a crop, with different subdivs, and see how times and quality behave.
The difference between the 3d effect and a post one (like a simple blur) is how the far things get more blurred than the closer ones.
If the view is quite simple, maybe you could also get away with interpolated refractions, with, maybe, even a -2 max interpolation, and higher subdivs (say twice the usual amount).