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762 Chapter 13: reactor
Point-Pa th Const ra int
Create panel > Helpers > reac tor > Point-Path
Menu bar > reactor > Create Object > Point-Path
Constraint
reactor toolbar > Create Point-Path Constraint button
The Point-Path constraint allows you to constrain
two bodies so that the child is free to move along a
specified path relative to the parent. Alternatively,
you can create a single-bodied version of the
constraint, where the constrained body can move
along a path in world space. The child body’s
orientation is not restricted by the constraint.
You could, for example, use a Point-Path constraint
to simulate a bead on a wire. In most cases, you
don’t need to specify a parent r igid body for a
Point-Path constraint, unless the motion of the
path itself should follow another r igid body.
The constraint is simulated if it has the correct
number of rigid bodies attached, a specified
path shape, and is included in a valid Constraint
Solver (page 2–736).Whennotselected,invalid
constraints are red in the viewport.
Pr ocedur es
To create a Point-Path constraint:
• Chooseoneoftheaboveoptions,andthen
click in any viewport to add the Point-Path
constraint.
Note: The icon’s position has no effect on the
constraint’s behavior.
To specify objects a nd a path for the constra int:
1.
Create the constraint and the bodies to
constrain.
2. Createalineorcurveintheviewportusingone
oftheShapestoolsontheCreatepanel.
3. Intheconstraint’sPropertiesrollout,clickthe
Childpickbutton,andthenselecttheobject
you want to use as the child object in one of t he
view por ts.
4. If you do not want to assign a second b ody to
the constraint, turn off the Parent check b ox
if necessary.
5. Iftheconstraintistobetwo-bodied,repeatstep
2, using the Parent pick button to set the parent
for the constraint.
6. Use the Path pick button to designate the path.
The constraint icon moves to the desig nated
path. By default, this constraint type is aligned
so that the parent constraint space is aligned
w ith the p ath shape’s local space, while the
child space is aligned with the child body’s
local space.
To change the path position and or ientation for the
bodies :
1.
With the constraint selected, open the Modif y
panel.
2. In the modifier stack open the constraint’s
sub-object list.
3. Access the sub-object level corresponding to
the object whose constraint space you want
to move: Child Space or Parent Space. If
the Point-Path constraint is single-bodied,
Parent Space represents the world position and
rotation of the path.
4. The space, represented by a set of axes and the
path, becomes active in the viewport and can be
moved or rotated using the Mov e or Rotate tool,
respectively. The space m aintains its position
and rotation relative to its corresponding
object. For example, if you move or rotate the
child body, Child Space moves with it.