Blender Hair/Fur & Feathers

Tommy Helgevold

Blender has an awesome particle generator that not only are capable of
generating particles, but is also capable of creating hair-strands that
can be used to create either hair, fur or even feathers.

This is achieved by converting the particles to renderable polygon strands.
The polygon strands never go below 1 pixel in size and this helps keeping
rendering artifacts at bay when the rendering engine renders the strands.

Let us begin by taking a look at the particle generator and how it works.
This is how the particle generator looks like in Blender 2.40:

fig-1:

As you can see in fig-1 you have many options. To find this particle menu
you must first create an particle emitter. The particle emitter can be just
about anything really... but it's a good idea to let it be an object. Let's
just start by adding a sphere: --> Space --> Add --> Mesh --> UVsphere.
Give the sphere around 20 segments and 20 lines. Exit to object mode --> Tab

Now go to your menu section and press F7 to get to the object menu. There you
will find a tab called particles. Press -->NEW and you will see the menu just
as in fig-1.

Since we're about to create hair-strands or fur we need to make the particles static.
Press static followed by animated if you plan to animate these later on. To draw
strands between each particle generated we need to activate "vector" under the
display section - press -->Vect. If you want the mesh to show during the generation
of particle strands you simply press -->Mesh under the display section.

We need to see the particles now but we haven't informed our generator how to emit
these from our mesh-object. To see these - go to the particle-motion tab and set
normal to 0.010. Your sphere should look something like in fig-2. If not, then press
the -->Z key to enter shaded view.

fig-2:

They look quite boring don't they? That's because they're just a bunch of strands
sticking out of a round ball, you can of course add these to any object you please.
Let's make them better looking! To do this we will need to make the strands ease out
and anti-alias into the environment around the object. We can even change the size
of the hair strands and how the tip will look like, but more about that later, let's
take a look at how we map the strands to look real soft and fluffy.

Strand Shader:

Blender's got a new shader! This shader has been implemented to follow the direction of
the new strand polygons. In other words if you select strand and place an texture or a
gradient - it will follow the direction of the strands. And we're going to use gradients
to shade the strands so they fade out to nothing - giving us an illusion of a much higher
resolution, this is known as anti-aliasing. You can't really render smaller than one pixel
anyway - so we use this "trick" to make the hair-strand tips smaller and fade into oblivion.

fig-3:

As you can see from fig-3 you're now in the material menu (F5). From there you need to
create a new material and add a texture, actually it would be practical if you create
2 materials if you intend to keep the original mesh-object as well as the particle strands,
but for now we will concentrate on shading the particles. Please make your selection exactly
as shown in fig-3. Strand activates strand mapping and Alpha activates the alpha channel.
The alpha channel contributes to making textures opaque and the texture background
invisible. This is the trick we discussed earlier to make the texture fade out to nothing.

Let's go work on the "fading texture". We're going to add an Blend gradient to our texture
slot-1. Check out fig-4.

fig-4:

Now we're going to add color gradients to our blend-gradient texture, press -->Colorband
to get to the next menu and make change the default colors to white and fade from
left to right (just drag the small line-markers in the gradient-window and slide
them to fit. If you've done everything correctly - things should look as in fig-5.

fig-5:

Ok, now we've made the gradients ready to help creating our fade effect on the
particle strands, go back to (F5) the material menu and untick the COL button.
The reason we do this is to make our own colors count instead of the color gradient
we made earlier. We just wanted to use that as a fade gradient from 100 % opaque to 0.

fig-6:

Now we're going to make a "hair" color, just go to the material menu and adjust the
colors as you see fit and slide the Alpha slider (A) to zero. We do this to make the
alphachannel gradient we made in fig-4 control our alpha 100%. You can of course adjust
this here to your liking if you don't want 100 % alpha, but do this for now.

fig-7:

If you did everything as described above and press F12 to render, your render
should look something like this:
fig-8:

As you can see - we now have soft "fluffy" hair strands, but we can do even more
yet before we add more particles. Blender have got yet another option under the
material menu called tangent-shading. The tangent-shader creates a thicker/thinner
hair/fur-strand curve depending on the lenght of your particle strands. You can adjust
it to make the strands start out or end thicker/thinner and how sharp/rounded they will
be.

fig-9:

I've set the shape to -0.900 so it's really "spikey".

And if you render it, here's how it would look:

fig-10:

Now that you've done all the footwork you're ready to have a LOT of fun with hair/fur,
let's go back to the particle editor and create a lot of fur.

In your particle menu - let's add a lot more particles...say 20000 of them, if you don't
have a very strong computer you can change the DISP value to display 20 percent or so and
when you play with particles, only 20 percent of them will show up in your viewport while
at rendertime - all particles will be present. Now that we have a lot of particle strands
let's add some weight to it. As we know...gravity goes downwards so we change the z-force
value to about -0.02 and to make our fur a bit frizzy and random looking - add 0.005 to
the random widget under the velocity section. To create an even better looking distribution
of our fur we could get our particles to emit from vertices and faces both randomly and
evenly, you can set this as in fig-11 under from.
fig-11:

If you render this, it will look something like in fig-12. If it doesn't, then
it's possible that your light-setup is very different from the one used in the example.
Ligths are very important to particle-strands, obviously because of shading. If you need
to do proper lightning then check out the lightning tutorials or lights section in the
manual and do this tutorial over again, you can get awesome results if you do your homework
when it comes to proper lightning.

fig-12:

Let's make hair with hairguides:
That's remarkably easy to do with the new guides, all you have to do in order to guide the
hairs in your new hairball is to add a curve and tell it it's a curve guide. To do that
Space-->Add-->Curve-->Bezier Curve and with the curve selected go to your F7 menu and take
a look in the dropdown menu found under the fields and deflection menu:

Now that you have selected it to become a curve guide you will see that it instantly affects
your particle furball. As you also might see - the shape of the hair is now conformed to the guide.
You're of course free to shape the curve any way you see fit, Blender will real-time update when you
move the bezier curve segments around and add new segments with -->E for extrude.

fig-13:

Again I cannot stress how important lights and shadows are to get quality hair, learn to do your
light setup well and you will be rewarded with lush and beautiful looking hair. A good way to get
shiny clean hair is to reduce specularity just a tad and increase the hardness value to about 70-100.

A thing you might want to do in order to render more lush "fluffy" hair is to select the Ztransparency
option found in the F5 Shader menu under the mirror transp tab. This will render the strands in alpha layers
with transparency making it antialias even better and give you totally awesome results, of course...this
WILL cost you render time but it's well worth it. You can use Ray-Transparency and set depth to whatever you
see fit - and it will render somewhat faster, but it won't look nearly as good as with Ztransparency.

fig-14:

Nice hair huh? Want to see the settings for it? Here you go, check out fig-15.

fig-15:

Let's take a look at what we've done to get that nice hair.
I made the previous object a bit smaller by scaling it so the start-emitter of the hair
would be smaller (just for effect - really). Then I blew up the Normal (speed) value found
under the particle motion section (velocity), gave it a little random-life (0.4) to vary
the speed a bit. I also scaled and moved around the bezier curve guide to affect the hair
try these variations - you'll be surprised how flexible it can be and how many variations you
can make.

Want to get even more advanced? Read on...

You can use multiple curves to guide your hair around. Make a duplicate of your
curve and tilt them both slightly as shown on figure f-16.

fig-16:

Now check out the F7 menu - fields and deflections again and press the "Additive" button.
This button creates an approximation field with your curve guides so when you blend two or more
together - it will affect parts of your hair-strands depending on your settings in Min-Dist and
falloff. Make a small min-dist value such as shown in fig-17 for both curves and experiment with
the falloff values (small numbers to start with). If you now mix these two curves together placing
them close to the hair emitter you can see the effect real-time and adjust the falloff/min/max-dist
values accordingly. These values will depend on your curves, number of segments and emitter size etc,
so in other words they will vary with your own creations.
fig-17:

If you've done everything correctly - you should be able to control your hair splitting it into
sections such as shown here:
fig-18:

As you can see from fig-18 you now have full control over where you put your hair.
You can even vary the lenght of each "curve" so it will affect the length of the hair
that are near the curve.

It doesn't end here - not by a long shot! There's nearly no end to how much you can control
your hair with Blender. You can twist it around, knit it, swirl it, toss it and yes
do anything you want with it. Become a world famous hairdresser - your characters will never
go bald again.