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152 Chapter 11: Space Warps and Particle Systems
object sur face. The Min value can not exceed the
Max value, and v ice-versa. If you try to raise Min
above Max, or lower Max below Min, both values
change equally.
Density by M ateria l—Varies emission over the
emitter surface based on properties of the material
applied to the emitter. For example, if the object is
assigned a black-and-white checkered diff use map
and you choose the Grayscale option, particles are
emitted only from the w hite checks.
Impor tant: For material-influenced emission to appear
properly in the viewports, two conditions are required:
• Atleastoneviewportmustbesettoashadeddisplay
mode.
• The material or map must have Show Map In
Viewpor t turned on in the Material Editor.
The options are as follows:
•
Grayscale—Thesoftwareinternallyconvertsthe
material-based coloring (diffuse) to grayscale,
and then emits more particles in lig hter areas
and fewer in dar ker areas.
The box emitter is mapp ed with a gradient. With Position
Object set to Density By Material > Grayscale, the particles
appear with greater fre quency in the lighter areas of the
box.
• Opa city —Particles are more likely to appear on
opaque areas than on transparent areas.
•
Grayscale & Opacity—Combines the two: More
part icles appear on light, opaque areas than on
dark, transparent areas.
•
Red/Green/Blue—Considers only the specified
color channel. T he higher its value at any given
pixel,themorelikelyparticlesaretoappear
there.
Use Sub-Material—When on, uses a sub-material
from the Multi/Sub-Object material assigned to
the emitter to define densit y values.
This option al lows usage of “inv isible” materials
for particle placement. If the emitter uses a
Multi/Sub-Object material but its geometry
doesn’t use the ID that corresponds to one of the
sub-materials, the sub-material doesn’t appear.
However,theoperatorcanuseittocalculate
the density of particle placement. The software
assumes the material to be applied to the entire
object surface.
Mtl ID—Specifies the material ID of the
sub-material to be used for particle emission.
Separation—When on, the software attempts to
keep the particles apart by the amount specified in
Distance. T he likelihood of successfully separating
particles depends on the number of particles, the
specified distance, and the Attempts Max value.
Distance—Specifies the dis tance, in system units,
by which the software should try to keep the
particles separate. Default=1.0.
Distinct Points Only—Limits emission to a specific
number of points (see Total, below) on the
specified Location type.
Emission points are sti ll randomized; change the
Uniqueness setting to alter these.