8

Using Mapped Materials with Particle Systems 237
Particles with a diffuse-mapped material
When you choose Icon, the mapping coordinates
of the material a re applied across the V (vertical)
axis, from V=0 (the bottom edge of the map) to
V=1(thetopedgeofthemap).Thebottomedge
of the map is applied at the birth of the particle,
and the top edge at either the death of the particle
(if Time is on) or the distance of the particle at its
death (if Distance is on).
TheTimespinnerspecifiesthenumberofframes
from birth that it takes to complete one mapping
of a particle. Thus, if set to 15, the par ticle uses
thebottomedgeofthemapatitsbirth,andmoves
through to the top edge of the map at frame 15.
TheDistancespinnerspecifiesthedistance,in
units,frombirththatittakestocompleteone
mapping of a particle. Thus, if set to 50, as the
particle moves along the normal vector, it displays
the bottom edge of the map at birth, and the top
edge at 50 units a long the normal vector.
The one exception to this is when you use the Tetra
part icle type. In this case, each part icle is always
constantly mapped with V =0 at the head and V=1
at the tail.
When you choose Picked Emitter, the particles
takeonthecoloroftheobjectatthepointatwhich
they’re c reated. If the mapp ed surface is yellow
where the particle emerges, then the particle is
yellow .
Again, Tetra particles are an exception and the
distribution-objec t material is mapped from head
to tail.
Fragment par ticles u se the same technique, with
additional options when the Thickness setting is
greater than 0.
WhenThicknessis0,allfacesinthefragment
are mapped the same as the portion of the object
surface from which they’re derived.
When Thickness is greater than 0, the outer
faces of the fragment copy the surface of the
distribution object, and are assigned the material
ID specified in the Outside ID spinner in the
Part icle Type rollout > Fragment Materials g roup.
ThethicknessedgesusetheEdgeIDnumber,and
the inner faces use Backside ID. Thus, by assign ing
a multi/sub-object material to the object-based
emitter, you can specify a different material for the
outer fragment surfaces, the edges, and the inner
surfaces. Note that the Outside ID spinner defaults
to a value of 0, which means "use whatever material
is currently assigned." Change this to a specific
sub-material number to assign a sub-material to
the outside edges of the f ragments.