Hair and Particle Systems - Blender Master Class: A Hands-on Guide to Modeling, Sculpting, Materials, and Rendering - page 126

Emit From (Verts/Faces/Volume) Determines
where hair particles are emitted from, such
as from the vertices of the mesh, scattered
over its faces, or from inside the volume of a
closed mesh.

Material This determines what material slot (in
the Materials tab of the Properties editor) the
hair particles will use. For example, if your first
material slot for the object is the skin material
for your model, you could set this to 2 and use
the second slot to define the hair material.

Random Emits particles randomly, ignoring the
order in which you created the faces of your
mesh. Leave this set to Random for hair.

Emitter When this setting is checked, both the
hair and its emitter mesh will render; when
unchecked, only the hair itself will render. This
setting is useful to disable if you are using an
object other than your “skin” object to generate
hair or if you're generating objects with a par-
ticle system and you want to render only those
instanced objects.

Even Distribution Scales the number of particles
emitted from each face according to the face's
area. Leave this checked, or large faces will
appear sparsely populated with hair when com-
pared to smaller faces.

Jittered/Random, Particles Per Face, and Jittering
Amount These settings control how the emis-
sion locations for particles are generated. The
default values almost always work well.

Parents If you are using child particles, this setting
will cause the parent particles to be rendered
along with the children.

None/Path/Object/Group This setting deter-
mines which renderable geometry the particle
system will use for particle generation. The
default setting of Path is used to create particle
hair, but a particle system can also be used to
create other kinds of geometry. Setting this
to Object will turn each hair particle into a
duplicate of the object chosen in the box that
appears, and setting it to Group will choose
objects from a group and duplicate them in the
same way. These options are useful for mak-
ing grass or for populating a surface with extra
details, like rocks or debris. The None option
will cause particles not to be rendered.
For hair, choose the Path option, which
brings up the following additional settings that
determine how particle hair will be rendered:

Velocity Panel
The settings in the Velocity panel basically deter-
mine how long your hairs will be and in what direc-
tion they'll point. The random and normal values
are most important here. Normal values cause hair
to point straight out from the surface, while random
values make the hair point in random directions.
Combining the two will allow you to point the hair
generally away from the head with the normal value,
while keeping a little roughness with the random
value. The other settings in this panel can be useful
if you want the hair to point in a specific direction
(such as straight up, using the Z value).

Rotation
The Rotation panel isn't particularly important when
working with strand-particle hair, but if you set the
render type for the particle system to Object or
Group, you can use the settings here to add random
rotation to the objects as they are generated. This
feature is a great way to prevent particle systems
that use the Object render type from looking too
repetitive by making it more difficult to recognize
repeated objects.

Strand Render This uses Blender's custom
strand primitive to render hair and fur in a
way that produces much faster results. The
downside to this rendering method is that
it's not compatible with ray-traced shadows,
so you will need to use spot lamps with buf-
fer shadows instead.

Adaptive Renderer This option for render-
ing hair is compatible with ray tracing and
optimizes the hair geometry, simplifying
bends in the hair so that long, straight sec-
tions use less geometry than more complex,
curved parts of strands. This keeps the total
amount of geometry used for hair to a mini-
mum and thus can speed up renders.

Render
This panel contains settings for how your particles
will be rendered in the final image. These settings,
listed below, will interact with the material we apply
to the particles later on in Chapter 12.