PDA

View Full Version : What's the best workflow for FiberFX if you want motion blur?



fahr
12-20-2012, 12:09 AM
I may be wrong about this, but FiberFX doesn't seem to support photoreal motion blur. If that's the case, then how is it being used in productions like Tera Nova? Did they not have motion blur at all? Did they render all their shots using multipass? Were they exporting 2d motion vectors and comping the blur in later? Does FiberFX support motion vectors?

If your hairy critters can't motion blur... well... that would really suck! How are studios getting around it? Or am I just flat out wrong and fiberfx supports photoreal motion blur just fine, you just need to flip that undocumented switch that's in there somewhere... ;)

Thanks!

Greenlaw
12-20-2012, 01:05 AM
In 11 sp3, you can output motion vectors for surface based fiberFX. For TerraNova, I believe the Pixomondo crew converted the Lightwave data into a merged RGB image for RSMB compatibility in After Effects. At the Box and at Little Green Dog, we can use the FiberFX vector data directly in Fusion if it's embedded in the EXR file.

IMO, using vector data to add motion blur in post is preferable to rendering with Photoreal Motion Blur because of the huge savings in render time. Yes, there are a few situations where it can produce an artifact but you can usually work around these, and often times the artifacts are not noticeable when played at speed anyway. In my experience at the Box at R+H, these situations come up very rarely.

FYI, in 11 sp3 and earlier, there exists a problems with FiberFX vectors when you use guide chains for long hair. A while back I had to create a lot of FiberFX hair for several human characters in a theatrical film production (sorry, not yet allowed to say what that project was,) and in this situation we expanded vectors from the 'hairless' character pass and clipped the expanded vector data using the alpha channel of the hair, and then used this modified data to blur the hair pass. This is a cheat but it can be a pretty effective one in many cases. Alternatively, you can use Polygonize to create real geometry from the hair and then render a separate vectors-only pass--this works but it's not completely accurate and, IMO, it's really not worth the effort. (NT is aware of this issue btw, so hopefully a proper fix will be coming.) If these cheats for 'long hair' vectors fall short of what you need, the next option is to render with PRMB (and maybe take the rest of the day off.) :)

Hope this helps.

G.

Greenlaw
12-20-2012, 01:12 AM
I should clarify something: I personally don't know if FiberFX in 11 sp3 works with PRMB because we always render our scenes without MB and use the vector data to mo-blur in post. To be honest, the last time I used PRMB was probably three or four years ago.

That said, if FiberFX isn't working with PRMB, I'm surprised to hear this. I'll take a quick look tomorrow morning and let you know what happens.

G.

fahr
12-20-2012, 09:10 AM
Thanks for the insight! I'll look into 2d vector passes. It sounds like theres a few hoops to jump through to get out a useable pass. Can you elaborate on how to get out a pass that works for rsmb in after effects? Thanks so much!

Greenlaw
12-20-2012, 10:19 AM
There's a free plug-in for exporting a RSMB compatible file. Here's the LWDB link:

http://www.lwplugindb.com/Plugin.aspx?id=694491bf

I think you just feed the vector image into the plug-in and it blurs whatever is in the main input. (I don't have any actual experience with this technique but there's plenty of info on the subject.)

Alternatively, I believe you can save a merged RSMB compatible version of data using that extra buffer export tool with a nodal setup from DP. I think there's a long thread on this topic so do a search for details.

That's about all I know for RSMB/AE compatibility--hopefully somebody who uses Lightwave vectors in AE will post more info.

Here's additional vector blur info just for completeness:

If you have exrTrader, you can embed vector data in an aux channel in an exr render. If you use Fusion, you'll want to redefine the channel names to get Fusion to 'autoload' the channels. Otherwise, you will need to manually add them to the Loader. Once the data is available to Fusion, it's simply a matter of adding a vector blur node somewhere after the Loader. Be aware the some tools and functions can mask or overwrite the data and you may need to pass the original data over any nodes in-between the Loader and Vector Blur nodes. (At work we have a handy tool called Vector Bridge for this--I wish it was native to the program so I could use it at home.)

At home, I've been perfectly satisfied with exrTrader. Even if you don't use embedded vectors, I recommend it highly. At work we have suite of proprietary tools for working with and manipulating vector data but in the end, the process is basically the same.

G.

Greenlaw
12-20-2012, 10:22 AM
Sorry, I posted a bad link above. It's fixed now.

G.