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176 Chapter 11: Space Warps and Particle Systems
Inter face
Par ticle Geomet ry group
Use this control for defining the object to be used
as the par ticle geometry. This object is known as
the
reference object
.
[button]—Click this button, and then select a
geometry object in the scene to be used as the
particle shape. The mouse cursor changes to a
cross shape when positioned over an object that’s
valid for use as a reference object. Valid objects
include
multi-shape
objectssuchasgroupsand
hierarchies; see
Separate Particles For group (page
2–177)
.
After picking a reference object, its name appears
on the button.
You can use almost any geometry object as
a reference object. By default, the operator
automatically conv erts closed splines to rendering
geometry by “filling in” the area defined by the
shapeoutline.Tousetheshapeoutlineinstead,
select the origina l shape and, on the Modify panel
> Rendering rollout, turn on Display Render Mesh.
You needn’t turn on Renderable, but changes to all
other R endering rollout settings, such Thickness
and Sides, are reflected in the rendered particles.
Particle Flow does not automatically “fill in” open
shapes such as Line (non-closed) and Arc. To
render t hese shapes when using them as particles,
turn on Modify panel > Rendering rollout >
Display Render Mesh.
If a Shape Instance operator is in effect for which
the geometry object is not defined, and the
viewport display type is set to Geometry, then the
particlesappearintheviewportsasXcharacters.
Note: If a multi-shape object used as a reference
object comprises objects both with and without
materialsapplied,andAcquireMaterialison,
P article Flow will apply the first available material
to any objects without materials applied.
Note: You can use a NU RBS surface as a reference
object, but not a NURBS curve. To use a NURBS
curve as particle geometr y, first convert it to a
surface using a method such as the Cap function.
Tip: For b est results, when using an animated
reference object, it’s highly recommended that
you hide t he original object before rendering, or
use Object Properties to turn off its Render able
check box.
Note: I f using a group as a reference object,
make sure the group is closed before selecting it.