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184 Chapter 11: Space Warps and Particle Systems
Inter face Contact Object group
Usethiscontrolfordefiningtheobjectonwhich
marks are to be left.
[button]—Click t his button, and then select an
object in the scene to use as the contact object.
The mouse cursor changes to a cross shape when
positioned over a valid object.
After picking a contact object, its name appears
on the button.
Align to Sur f ace Animation—When on, Shape Mark
takes into account surface changes due to vertex
animation of the contact object. If Shape (page
2–185) is set to Rectangle, then the mark changes
its orientation and position to appear be stuck to
the surface of the contact object. If Shape is set to
Box Intersection, then the mark changes shape
along w ith that of the contact object. When off,
only transformation of the contact object is taken
into consideration. Default=off.
Turn this on only if there is significant vertex
animation at the contact point, such as with an
animated water sur face.
Wa rn in g : This option requires significant CPU and
memory resources.
Orientation group
Align To—DependingonthesettingforShape
(page 2–185),ShapeMarkcreateseitherarectangle
or a box cutout on the con tact geometry. The
Orientation setting specifies how the shape is
oriented. In the mark’s local coordinate system,
the X axis is Length, the Y axis is Width, and
w ith the box cutout, Z is height. The Z axis is
perpendicular to the surface of the object at the
contact point.
The alignment choices are as follows:
•
Speed—The L eng th direction is parallel to the
projection of the particles’ speed vector onto
the contact plane.