2d Motion Blur

[ktysdal]

I've been trying to find a good resource on how I can achieve a decent post effect motion blur with XSI, but I just haven't been able to find anything. The manual pretty much only says that the 2d motion blur went away after xsi 4.2 (btw why did that happen?).

So can anyone try to explain the workflow of doing 2d motion blur? it would be much appreciated

thanks

[pboucher]

One of the workflows I have seen quite a bit of is one involving a motion vector pass:
http://www.alamaison.fr/3d/lm_2DMV/lm_2DMV_ref.htm
and 2d motion blur in comp:
http://www.revisionfx.com/products/rsmb

[NagyG]

MR float Motion vector shader :
http://www.melon.hu/Gergo//MVector/MVector_V1.rar (http://www.melon.hu/Gergo//MVector/MVector_V1.rar)


http://www.melon.hu/Gergo//MVector/MVector_V1.mov (http://www.melon.hu/Gergo//MVector/MVector_V1.mov)
http://www.melon.hu/Gergo//MrMv/renderoption.mov (http://www.melon.hu/Gergo//MrMv/renderoption.mov)
http://www.melon.hu/Gergo//MVector/mvonhair.mov (http://www.melon.hu/Gergo//MVector/mvonhair.mov)

[Gfxman]

MR float Motion vector shader :
http://www.melon.hu/Gergo//MVector/MVector_V1.rar (http://www.melon.hu/Gergo//MVector/MVector_V1.rar)


http://www.melon.hu/Gergo//MVector/MVector_V1.mov (http://www.melon.hu/Gergo//MVector/MVector_V1.mov)
http://www.melon.hu/Gergo//MrMv/renderoption.mov (http://www.melon.hu/Gergo//MrMv/renderoption.mov)
http://www.melon.hu/Gergo//MVector/mvonhair.mov (http://www.melon.hu/Gergo//MVector/mvonhair.mov)

I, what kind of effect is he using in post ? is a plugin or a native effect from combustion (? is tha software combustion ? ).

What would be the effect in after effects? And what is the difference between this and lmaison2D vector shader ?

[MartinWeber]

I, what kind of effect is he using in post ? is a plugin or a native effect from combustion (? is tha software combustion ? ).
Looks like Fusion and if you look hard enough you can see that one node is called "ReelSmartMoti..." which would be the ReelSmart Motion Blur plugin (Patrick Boucher posted the link (http://www.revisionfx.com/products/rsmb/) above).

[Gfxman]

Looks like Fusion and if you look hard enough you can see that one node is called "ReelSmartMoti..." which would be the ReelSmart Motion Blur plugin (Patrick Boucher posted the link (http://www.revisionfx.com/products/rsmb/) above).

thx a lot, so it's the same as lamaison, witch, really never worked very well to me :( I'll try this shader too!

[guillaume]

thx a lot, so it's the same as lamaison, witch, really never worked very well to me :( I'll try this shader too!

lm2DMV just works well as a 2D motion vector shader. Can you explain why it doesn't for you ?

Cheers

[lee]

The lamaison solution can work really well but it's true that if you don't have somebody to help you set the shader parameter the first time, it's not very clear how to get a result.

Any post-process 2D blur can work well for objects moving with simple translation and no internal deformation. However, if you have for example two characters fighting kung-fu, with arm and leg rotation and overlapping body parts, most 2D blur solutions won't work well because they can't distinguish the scene depth of the moving objects. Sometimes you have to create multiple passes to separate the layers to get the 2D blur to work; but after all the pass-creation work and new layers in your composite, it might have been faster to just render a 3D blur...

[Nightwalker]

Thats an interesting discution, is it possible to use the lamaison method without using any plug ? I.E. in the fxtree ?

And if I chose to use 3d mblur, can I still have control in comp over the diferent object and material IDs ( max jargon..channels in XSI ? sorry i'm new to xsi ...) ? wont the premultiply be all messed up ? I wont be able to create a mask from an ID would I ?

[cryptosporidium]

dudes, try to avoid 2D mBlur. It just doesnt work in most situations. 3D mBlur worth it even for that render time, if you can afford it.

[CiaranM]

dudes, try to avoid 2D mBlur. It just doesnt work in most situations. 3D mBlur worth it even for that render time, if you can afford it.

If you have all the time in the world, sure. I won't pretend that 2D blur is perfect, but in most cases it will look "good enough". More so since objects with motion blur will generally be moving relatively fast and imperfections, though we the artist know they are there, are not going to be noticed by 90% of the viewers.
Also, don't forget the power of adjusting in post. I'd rather have the flexibility to be able to reduce my blur by 50% at the touch of a button, than have to endure expensive re-renders. This is especially pertinent to those of us without access to huge render farms (or 3Delight!).

[cryptosporidium]

CiaranM: i dont pretend 2D mb is useless :-) All im telling is that you cant compensate 3D mb in 2D. For sure it depends what are you rendering, for what purpose. In some simple cases 2d mb works just fine, in many others it works more or less, with artifacts and its up to you and a customer whether its good enough or not (but when you work in film industry, answer will be "no, its not good enough"). And in many other cases it just doesnt work at all - when you have objects that rotates fast or when objects goes across each other for example. But of course, as allways its price vs. effeciency and sometimes 2D mb can really save your ass ;-)

[lee]

The best solution is the one that looks good enough and delivers on time! My production experience is that 2D blur would work well for example with a jet plane flying by; no internal moving parts. But it wouldn't work well with a car driving by where you could see the wheels turning; the rotations look really bad in 2D blur. However, if you're doing a 3D environment and you're only blurring with the camera movement, 2D blur could work really well. So for example you could split a full-3D render and blur your character in 3D and the surrounding environment in 2D and save a lot of time. To answer the question regarding element ID renders, as long as you apply the same 2D blur to the ID and color pass, it should work fine.

But the real problem is that mental ray's 3D motion blur (as implemented through XSI) HAS NO INTELLIGENT OPTIMIZATION which is really freaking sad. What we need is something like Renderman's Motion Factor, which reduces surface shading rate based on screen speed (i.e. THE FASTER IT MOVES AND THE MORE MOTION BLUR, THE FASTER IT RENDERS!!!!).

[CiaranM]

But the real problem is that mental ray's 3D motion blur (as implemented through XSI) HAS NO INTELLIGENT OPTIMIZATION which is really freaking sad. What we need is something like Renderman's Motion Factor, which reduces surface shading rate based on screen speed (i.e. THE FASTER IT MOVES AND THE MORE MOTION BLUR, THE FASTER IT RENDERS!!!!).

Sounds interesting. Is there such a method in MR that is not exposed in XSI?

[lee]

Can't say for sure. I just went searching online and found a mental ray user's group posting from november 2006 asking for Motion-Factor in the next update of mr, but I haven't seen any mention of it since then. I think if they implemented it in mr, there would be a fair amount of buzz about it... But I'm not sure if it absolutely has to be implemented in mr; I wonder if XSI could implement something as a camera shader that would reduce object-surface shading samples in situations of fast camera-object relative movement, and then pass this on to mr.