Any info on MotionBlur button!

(skodela) #1

Hi folks

Does anyone has any info on MotionBlur button. The Blurfactor ofcourse [as I understand ] will affect the motion blur. But it is not very clear in a simple animation. A complex animation just to check will take weeks to render on my poor old system.

Does anyone have any info on how Blurfactor affects the MotionBlur.

Many thanks
sreekant :x

(kattkieru) #2

Basically, the BlurFactor sets how blurry objects in motion are. A higher blur factor makes really blurry images, but a lower factor makes them less blurry.

It’s like the shutter on a camera. If you leave it open longer, you get a blur across the film with moving subjects. if you set the shutter speed really high, and use high-speed film, you get less blur on high-action shots.

Does that help? I find that for most animations a setting between 0.500 (the default) and 1.0 yields the best blur. A good way to check, if you’ve got a slow computer, is to animate a ball moving around the screen, and then only render a frame here and there. The frame will still be motion blurred because Blender does motion blurring based on samples of the motion before and afterwards, as far as I can tell.

(skodela) #3

Many thanks


(theeth) #4

the Bf value is exactly like the shutter of a camera. It is the time, in frame, between the blur starts and end. The numbered buttons under OSA determines how many pictures will be combined together.

I hope that was clear.


(Jamesk) #5

An additional hint: If you use a fairly high setting under the OSA button, say 11 or 16, you may very well turn off the OSA itself since you will rarely get any aliasing problems thanks to the blur and the overlays of subframe renders. This speeds up the render quite a bit if there’s a lot of geometry in it.

(kattkieru) #6

That’s only partially true. OSA is still required for scenes with a mobile object, but a static background. The motion blur only blurs objects in motion (or the whole scene if your camera’s moving), so if you’ve got one jumping chess piece on a complex static background, the chess piece will look great and the background will be aliased all over the place.

(eeshlo) #7

Actually, Blender also jitters the camera position with motionblur enabled, wether OSA is switched on or not, in fact this a good method to improve anti-aliasing. Use motion blur in a static scene with OSA enabled and you will square the number of samples used for the OSA.
So a value of 16 for OSA/Motionblur will be equivalent to 256 OSA samples. Just try a test with a slightly rotated black square on a white background to see the difference.
Cessen posted this sometime ago either here or on the old forums, and he got it directly from Ton himself.

(Dittohead) #8

it should however be turned on when you have bumpmapped objects in the scene.

(Jamesk) #9

True, true!

(kattkieru) #10

Wow… the camera jitter is great! I think it’s the same effect as the one used by Pixar to make their static scenes not appear static. Thanks for the tip!

(CubeFan973) #11

BTW: If someone’s mentioned this, excuse me for being ignorant. If someone hasn’t mentioned this, I don’t have a clue of why, but under OSA are the numbers 5, 8, 11, and 16. These give your MBLUR renders a different amount of time to render. 5 means 5 frames will be rendered for the MBLUR, 8 means 8 frames, and so forth. This limited number system, in my opinion, sucks–why not have a slider ranging from 3 (3 frames might work for really crappy MBLURring) to 17,576 (gosh, I love that number–it was literally a plot point in “Cube,” it’s not too high but not too small, and it fits if you’re trying to get the point of a huge number across)?

That number system, by the way, also affects your MBLUR renders. It looks poorly basic at 5, and it looks best at 16. You get the idea.

Didn’t know about that camera jitter, cool! Can’t even notice it in the renders!

(kattkieru) #12

I thought the OSA numbers were for oversampling itself and not for blur sampling?

(eeshlo) #13

Yes, the numbers are used for motion blur as well. What blender basically does is average a ‘OSA number’ of frames over a Bf frame time interval. So when the button numbered 16 under OSA is enabled and the Bf field is set to 0.5, Blender will add and average 16 frames starting at time t + 0.5/16 and ends at time t + 0.5 (16*0.5/16). And every frame, like for anti-aliasing, the camera is jittered as well, a slight (at subpixel level) change in position. But I’m really just guessing of course… :wink: