Realistic Fur Pipeline

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Old 04 April 2009   #16
Hi guys,
I'm rendering some fur for a short film I'm making with Matt Beech called Static. I'm using p_hairTK with Max and Mental Ray. I've found GI is basically unneccesary - I think the difference isn't worth it using this shader (and the relevant puppet hair shadow shader). I'm finding it really quite quick to render. My flow is to render out the scene without the fur object (using all my usual GI-included tricks), then render a shadow pass for the furr object, then render all the lighting passes for the fur separately. What I found is that if too much light is seen straight on, it begins to look too uniform in colour, yet the terminator looks lovely. So what I've taken to doing is rendering off basically a bunch of different lights (all without GI, as said) then comping them together afterwards. The only problem I have found is that I can't get UVW mapping to work with it in Max. I know it's possible in Maya, so maybe I'm just missing something.

Here's a short video of the object turning, but this is with a very old version of the fur (with no spec, I believe) but I think it looks OK and no flickering:

http://www.youtube.com/watch?v=rnrzidYw4Ig&fmt=22

And here's a link to a still using the latest version of the fur we have, which will mostly likely be the one we use for final renders. It's by no means perfect, but time constraints have meant we have to press on. There are about 7 different light passes that comprise this image:



(Click to view thread)
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Old 04 April 2009   #17
had to edit the post for some reasons

Last edited by Rainroom : 04 April 2009 at 03:10 AM.
 
Old 04 April 2009   #18
Quote:
Originally Posted by Rainroom
As far as rendering realistic fur is concerned I believe that using Deep Shadow Map is the way to go for shadows. For rendering ambient occlusion on the fur a 16/32 lights dome-setup with soft-shadows around the character can give you satisfactory results with fast render-times.


^^This. Here we use a combination of a dome for environmental illumination, and a short-distance, pre-baked, static hair-to-hair occlusion for extra detail.
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Old 04 April 2009   #19
I've spent hours and hours with shave and appreciate this thread cos hair does seem a real tricky one to get right. :P What I'd like to know is... in a production environment, how much time do you guys set aside for developing a working hair pipeline? Just like to know the man hours that goes into something like this.
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Old 04 April 2009   #20
Quote:
Originally Posted by Yeminius
do you have any example of an animation you've done with shave?
I haven't yet seen any realistic animation made with it. Other than King kong, I have no other good reference :(


Shave was used to initially style kong's fur while we came up with our own tool for sculpting hair within Maya. It was only used for a very specific purpose on Kong, which was to style the guide curves, by the time we were putting Kong into shots we had come up with our own sculpting tool called 'Combover'.

The fur is styled using a series of deformations - primarily procedural deformations such as noise, bends, clump and twirls - all of which could be applied to other deformers. For example a noise deformer could act on each hair individually or it could act on a clump strand, each producing a different effect. As well as procedurally styling the hair it can also use more explicit control such as by connecting guide curves to specific deformers - this is where Shave and now Combover comes into it.

The program (bonobo) that actually creates and deforms the hair is proprietary code that was designed to handle the large amount of hair on Kong in an efficient and speedy manner. It was able to interact with Maya and PRman via plugins in order to be simulated for dynamics (movement, collisions, wind, water), shaded, lit and rendered.

Bonobo was also able to generate and render 'mud, blood and debris' within the fur using either particles, metaballs and geometry depending on the type of substance that got stuck - for example snow used particles, water used metaballs and plants used geo.

As far as being lit (and to potentially answer the original question), it was done using spots with deep shadows as well as ambient and reflection environment lights. Occlusion for the hair was static and baked into brick maps.
 
Old 04 April 2009   #21
Quote:
Originally Posted by vfx
What I'd like to know is... in a production environment, how much time do you guys set aside for developing a working hair pipeline? Just like to know the man hours that goes into something like this.


Depends. Lots.

The current Weta Fur system (which replaced two previous systems I believe) was developed during Kong over about a year and a half during the production of the film. The next few years after that was mainly refining the system to make it quicker and easier to use, there was some work put into making it work for different styles of hair, but that was mainly artistic choices - like how do you make CG dreadlocks (White Witch in Prince Caspian), which required a couple of new procedural deformers.

Mainly it was your typical pipeline refinement stuff - what can be automated using scripts, how stuff is named, where it's placed on the network, what tags does it need, what information needs to be passed on, what settings need to be set. Attribute tagging was preffered where ever possible over naming conventions as it wasn't as open to user error.
 
Old 04 April 2009   #22
MPC's fur pipeline has gone through several iterations too. The latest incaration, 'furtility', was developed for 10,000B.C., massively revamped for Caspian and has been in constant development since. By the sounds of it, it shares a lot of features and workflow as weta's system - probably because it's the most sensible way to do a grooming tool. If you search 'furtility' on vfxworld.com there's a few articles which mention it. Now we use it for doing lots of set-dressing tasks as well as fur and feathers.

For rendering we use dome lights for IBL and traditional lighting for the rest. We use a custom hair shader that's similar in spirit to the Marschner model, but much simpler and easier to control.
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Old 04 April 2009   #23
frankly to me you can have all the fancy siggraph shaders but the one important factor is selfshadowing. The one reason people use renderman is the deepshadows feature.
And yes the ability to quickly implement a mashner or muhair shader is easy in prman...

oh btw there is a houdini thread about fur on odforce...
http://forums.odforce.net/index.php?showtopic=2208
 
Old 04 April 2009   #24
Quote:
Originally Posted by darktding
And yes the ability to quickly implement a mashner or muhair shader is easy in prman...

As long as you realize that muhair is just the name that Daniel (Rind) gave to the shader he wrote, and not a shading model, and that mashner is "Marschner", I'm sure all will be fine and you won't need anything except deep shadows
After all it's not like the look contribution of the specular model on hair has any importance for 90% or more of the situations where you need hair or fur right? Or that finding an efficient way to transmit reflection occlusion to it without calculating it per filament brings any advantages...
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Last edited by ThE_JacO : 04 April 2009 at 02:07 PM.
 
Old 04 April 2009   #25
Quote:
Originally Posted by ThE_JacO
As long as you realize that muhair is just the name that Daniel (Rind) gave to the shader he wrote, and not a shading model, and that mashner is "Marschner", I'm sure all will be fine and you won't need anything except deep shadows
After all it's not like the look contribution of the specular model on hair has any importance for 90% or more of the situations where you need hair or fur right? Or that finding an efficient way to transmit reflection occlusion to it without calculating it per filament brings any advantages...




We don't do reflection occlusion at all thank god, and skip ambient occlusion most of the time. That's the wonderful thing about dome lights...

And implementing the Marschner model is most definitely not easy in prman. You have to go through a lot of calculus and there are several mathematical errors in the paper.
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Old 04 April 2009   #26
Thanks guys, very useful info.. just goes to show, hair will always be a difficult task for an individual if trying to compete with the likes of the top FX studios.
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Old 04 April 2009   #27
Quote:
Originally Posted by Yeminius
@MikeRhone

Some months ago I tried muhHair, but never made it to work. At least not in maya 2008 or 2009..


Ya, muhHair was hard to get going for sure. Unfortunately I wasn't the one working with the fur, so I don't know what they did to get it to look as nice as it did. I just know they used muhHair. The p_hairTK seems to be the next step forward and shows a lot of promise to me. The other posters in this thread have taken fur a lat farther than I have personally, so I'm afraid I don't have much more to add.
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Old 04 April 2009   #28
Quote:
Originally Posted by playmesumch00ns


We don't do reflection occlusion at all thank god, and skip ambient occlusion most of the time. That's the wonderful thing about dome lights...

Agreed, dome lights are a blessing for that and to enforce first pass consistency across a sequence, I'm surprised though you don't transmit occlusion from the emitter for short fur.
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Old 04 April 2009   #29
This is all very interesting.

Just to get it back to the small studio context. What is the benefit
of using a dome light over say, an env light or even the quicker ways
of getting env light using spherical harmonics or even a point based
method in PRman.

Does a dome light just end up being more efficent in the long run?

Dome lights generate lots of shadow maps which in turn bump up
render times a lot when you only have a few machines. I did two jobs
with fur last year and I had to jump threw hoops just to get them out the
door.

I am currently doing a project that should have fur but I'm reluctant
to use it. I have over 9000 frames to render on a small amount of
machines. That is tough enough. Adding fur just seems like a lot of
trouble for me further down the line.
 
Old 04 April 2009   #30
Quote:
Originally Posted by ThE_JacO
Agreed, dome lights are a blessing for that and to enforce first pass consistency across a sequence, I'm surprised though you don't transmit occlusion from the emitter for short fur.


Well if you're using a dome then you don't want ambient occlusion or you'll be doubling up environment shadowing. Actually I hate ambient occlusion. People seem to think you just turn it on and it makes your scene look better but it ends up just making everything look dirty. The shadwing doesn't respect the incident light distribution and that always looks fake.

We have two methodologies for shadowing fur -
1) Just use deep shadows on the dome and be done with it. This of course leads to some pretty long rendertimes but the results are beautiful
2) Use the trick Pixar described in their Ratatouille presentation at the RUG the year before last(?): use standard shadows containing just the skin to get the overall shadowing and then mult in a short-distance ambient occlusion. This is obviously much faster than 1) but you lose some really nice light effects in the shadow region because you're again ignoring the directionality of the light. It's still much, much better than using a full-on diffuse environment light with ambient occlusion though.

art_3d: 9000 frames of fur on a handful of machines? Ouch! Don't do it!
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