Method for soft looking fur

#1

Some people might remember John Keates came up with a method to soften the look of Hash hair without resorting to options like increasing density, and making the hair finer and more transparent.

Well, I needed to make a CG cat for work, but struggled to make the fur look soft and fluffy. So I used John’s technique of moving hair guides side to side in an action, importing this action into a choreography, setting it to repeat several times and then sliding back the action’s red bar in the timeline to reduce it’s cycle length. This means the hair will ‘jitter’ about on sub frames… like a spinning light rig. You can also jitter the hairs ‘positional variation’ value using the same trick.

I think John could better explain the technique in more detail, but here’s a close up shot of my cat’s fur, I’m afraid, for commercial reasons, I can’t show the whole picture just now.

It’s not perfect, but it’s getting there. A clumpiness setting for A:M fur would really help improve the realism. Oh, and this jitter trick is ideal for animation as it’s doesn’t significantly increase render times, unlike the alternatives of ramping up the fur density.

#2

Wow. Very nice. Spinning hair guides. Thats. . . some freaky crap.

#3

That might not be perfect, but it’s da,m close. Great work. Tell John to post a mini-tut or something.

#4

Wow that looks real nice. Does it look ok animated?

#5

Hi Guys, Glad you like the technique.

Pequod gave a pretty good explanation so I don’t really know what to add - other than to make sure that you use motionblur in multipass to make it work.

There are potential problems when using it in animation but no more than is the case when using spinning light rigs or soft shadows or whatever.

It is possible to set the jitter action so that it has only four positions (for example) and then you would have a more reliable technique which would look the same if you have 4 or 24 passes.

The technique is worth using because you end up with better looking hair (transparent) and there is more of it - all at no cost to render time. That is a lot of gain for only a smidgeon of work.

It would be good if the hair position seed thing was exposed so we could use that to jitter the position of the hair. The “position variation” just moves the hairs from a random layout to an ordered one and so doesn’t cover all positions on the skin.

Another effect to watch out for is that the hair can appear brighter because each hair is only shadowed by those other hairs that appear in that part of the jitter cycle. This is no bad thing really.

I thought of this method when trying to find ways of speeding up a render when using Translucency. I find that hair can look really nice with a backlight and translucency but render times are really nasty. With this technique, translucency is more viable.

Another thing to watch for is that the hair can look quite different in 12 if you are using specularity as it is possible to have a ‘brighter than white’ specularity in v12 wheras the highlight in each pass gets watered down in v11 resulting in little final effect.

I have attached a demo project. I made two poses, each for moving the hair allong one axis, then I animated them allong with position variation in an action and set the action length to 0.25 in the chor. You have to use multipass motionblur at 25% for it to render properly.

It is of course possible to jitter different areas of a model seperately for more tweek control.

  Feel free to ask further questions.
#6

Hi John,

Thanks for the info, sounds like a very powerful technique. :slight_smile:

BTW, I don’t see the demo project that you said was attached.

#7

Oooops! Sorry. I forgot to press the buton. All forums seem to work differently. It is there now.

#8

Hey Steve,
looking at your hair example (lovely by the way), some parts have more jitter than others and this makes some bits look like they are more dry. It is like she just licked some parts. This is pretty cool and adds some nice variation.

#9

Whoooa! Pretty cool!

#10

Wow, very nice Stephen. Did you use Translucency on the hair at all?

Kevin

#11

That rocks, Stephen! Kudos!

#12

I’m glad you guys like the look of the fur.

The hair material itself is fairly standard stuff, so no need for translucency. I do have about 20% transparency on the longer guard hairs. I suppose if you wanted to get some nice backlighting, then a combination of the two might help, but I haven’t been too successful in this area and boy… the render times are a little soul destroying

You’ll need the latest version of 11.1(i) or 12 if you want short, light coloured fur like this to render without any nasty black shading anomalies. Essentially, the hair has to ‘Face Camera’ and a new setting in the hair properties ‘Brighten’ has to be turned on. I’m very grateful to Hash for fixing this.

The disadvantage of having all the hair facing the camera, is it’s a little tricky for the hair to pick up any colours from side lighting.

Here’s the main hair material I used:

Fur material

Oh, the subtle colour in my fur was driven by a decal and not from the hair emitter.

#13

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