Multipass and Motion Blur Together

[detbear]

Hey Everyone,

 

I have my render settings with Multipass at 25 passes and I also have Motion Blur ON at 20%... Should I avoid having motion blur on at all since I'm using Multipass???

 

William

[robcat2075]

Hey Everyone,

 

I have my render settings with Multipass at 25 passes and I also have Motion Blur ON at 20%... Should I avoid having motion blur on at all since I'm using Multipass???

 

William

 

 

Put it ON if you want motion blur. Otherwise A:M will do all 25 passes at the same moment in the timeline, which might still be useful for anti-aliasing purposes or things like light or hair jitter.

[detbear]

I just want to make sure that the areas of "Lesser" motion remain as "Crisp" as possible without also having some blurr...

 

At 1280 x 720 I'm not sure if 25 multi-passes is enough... But it is a LLLLooooooong render.

 

William

[John Bigboote]

A:M has two different ways of generating motion blur...one in multipass and the other in the standard renderer. The better of the 2 would be multipass...as Rob mentioned it actually interplolates the differences from frames to frame- so with 25 passes there would be 25 motion blur samples to blur together...which is pretty good! The parts of the image that do not move will also benefit from 25 passes of antialiasing...for smoother edges.

[detbear]

A:M has two different ways of generating motion blur...one in multipass and the other in the standard renderer. The better of the 2 would be multipass...as Rob mentioned it actually interplolates the differences from frames to frame- so with 25 passes there would be 25 motion blur samples to blur together...which is pretty good! The parts of the image that do not move will also benefit from 25 passes of antialiasing...for smoother edges.

I know I want the Multipass setting on, but should I just go ahead and shift the Motion blurr off... It's a 24frames per second shot.

[John Bigboote]

Entirely up to you. MB does not add (too much) to render times... it gives a nice, natural blur to faster-moving scene elements...do you want that?

[robcat2075]

Motion blur won't add any time to a multipass render. It will be tediously long either way.

 

The simple motion blur of regular renders only adds a few seconds.

 

regular renders have anti aliasing equivalent to a 16 (4x4) multipass but faster.

 

If better anti aliasing is the reason for going to 25 passes (still only 5x5) and you DON'T want motion blur, I'd consider a double size regular render and scale that down to normal size with a batch action in Photoshop. That would be anti-aliasing equivalent to 64 passes (8x8) and MUCH faster than the multipass route.

 

IF you have the RAM for the large render size.

[detbear]

Hey guys,

 

That's awesome information. Thanks for your help. For this sequence I'm going to go ahead and keep the Motion blur and Multipass in there. I guess I'll just have to take some extra long lunch breaks for the render times... Well more like days away from the computer... The results are worth it. I am in the process of trying to get Net render on my machines which will obviously help.

 

William

[Rodney]

As has been mentioned you get a lot of things for free when you have Multipass on.

Once Multipass kicks in and does its required calculations its all about moving the numbers it's stored around in its little virtual world.

So adding additional options doesn't effect render times much.

 

Here is what Greg Rostami had to say about it a long time ago:

 

Since there is been some talk about multi-pass rendering, I thought I would show my enthusiasm and support for this concept and also shed some light on all of the benefits of this very COOL technologie.

 

Here is a list of all the things you get with multi-pass rendering.

1. True Motion Blur (anything that moves will motion blur) with controlable quality.
   
2. True Depth of Field with controlable quality.
   
3. Very High quality anti-aliasing once again with controlable quality.
   
4. Incredible Area Light sources (Any Spline can be a LIGHT!) without using multiple lights or multiple shadow rays!?
   
5. Fuzzy Reflections and Refractions with controlable quality.
   
6. No need to use Filter or Anti-Alias option in Rendering.
   

BTW, ALL of the above features happen AT THE SAME TIME. That means if you turn on any one of these features you can get all of the other ones for FREE! (meaning there will be no extra hit in render times.)

 

THIS IS ALL CAPS BECAUSE IT'S REALLY IMPORTANT. MULTI-PASS RENDERING IS SLOW. AS THE QUALITY OF MULTI-PASS GOES UP SO DOES THE RENDER TIMES. IF YOUR NORMAL RENDER WITHOUT FILTER TAKES 30 SECONDS/FRAME, WITH MULTI-PASS SET TO 16 IT WILL TAKE 8 MINUTES! WITH MULTI-PASS SET TO 25 IT WILL TAKE 12.5 MINUTES! BUT, BUT, BUT YOU MUST REMEMBER THAT YOU GET ALL OF THE ABOVE AMAZING FEATURES FOR FREE!

 

Since I'm listing all the things you GET with multi-pass, I should also mention all the things you DON'T GET when you don't have multi-pass.

1. Pixel Streaking Motion Blur (only works on moving objects) i.e. shadows, reflections, transparencies, animated textures, lens flares, glows WILL NOT motion blur.
   
2. Post Blur Depth of field (sometimes produces unwanted halos around objects).
   
3. Non-User controlable Anti-Aliasing (you only get one setting on or off).
   
4. Very slow area light sources that only produce Area shadows, NOT true Area light source effects.
   
5. Fuzzy reflections and refractions can only super sample to one setting (the default that you can't change)
   
6. The need to use filter that gives you one default super sample setting that once again you CAN'T CHANGE.
   

Turning on any of the above features WILL add to your render times; unlike multi-pass where ALL of those features are FREE.

 

Greg Rostami

 

 

...and no... short of Xtas's MOOFUF spinning geometry lighting tricks I'm still not sure what Greg meant by 'every spline can be a light'.

 

 

I did run into this quote from Raf Anzovin which makes me wonder about Motion Blur:

 

 

The multipass render method is much superior to A:Ms native motion blur, which is really fast but also inaccurate. It looks wonderful--but expect it to send your render times way up. It literally renders the scene a number of times (eight or so is usually the minimum for a good blur) and puts them together to create the blur. I use regular motion blur whenever I can get away with it, but for some fast motions multipass blur is really necessary.

 

--Raf Anzovin

 

So, what to take from all of this?

I'd say, make sure you have some good motion to blur.

[John Bigboote]

Wow! Leave it to Rodney to find quotes from two legeonds! I hope Raf and Greg are doing well these-here-days.

[Paul Forwood]

Great post, Rodney! I often wonder what I am missing by sticking at the 3-5 pass mark. Isn't there a feature that doesn't kick in until the 5 pass mark? I vaguely recall some mention of this a long time ago but can't recall what it was. Maybe it was hair jitter or something to do with Depth of Field? Anyway it is good to be reminded of those points. Thanks!

[robcat2075]

Great post, Rodney! I often wonder what I am missing by sticking at the 3-5 pass mark. Isn't there a feature that doesn't kick in until the 5 pass mark? I vaguely recall some mention of this a long time ago but can't recall what it was. Maybe it was hair jitter or something to do with Depth of Field? Anyway it is good to be reminded of those points. Thanks!

 

"Soften" goes ON by default (but can be turned OFF) with 4+ passes. That does add time.