Graphics Reference
In-Depth Information
Using Rigid Body Joint Constraints
In Blender, you can set up joints by using the Rigid Body Joint constraint found in the Constraints tab of the
Object Properties area. To get an idea of these, start up a fresh session of Blender, duplicate the default cube,
and move the new copy, Cube.001, along the x-axis so that it is next to the original cube with a small space
between them.
1.
Withthenewcubeselected, selecttheRigidBodyJointconstraintfromtheAddConstraint drop-down
menu, as shown in
Figure 8-49
.
Figure 8-49
Rigid Body Joint constraint
2.
TheoptionsforthetypeofjointareBall,Hinge,andGeneric.BallandHingeareball-and-socketjoints
and hinges (respectively) along the lines of the earlier diagrams. The Generic joint option enables you to
set numerical restrictions on six degrees of freedom, three axes of rotation, and three axes of translation.
This enables you to not only represent slider joints but also to lock or restrict movement to a specified
range for each degree of freedom. For this example, select Hinge.
3.
Set the Hinge parameters as shown in
Figure 8-50
.
The Target field is for the object that the hinge
attaches to, in this case the first cube. Display Pivot makes the constraint's pivot point visible in the 3D
viewport.PivotX,PivotY,andPivotZlocatethepivotinspacewithrelationtotheobject'scenter(meas-
uredinBlenderUnits).TheAxisX,AxisY,andAxisZrotatetheconstraint.TheHingeconstraintrotates
around its own x-axis; therefore, to line the hinge up along the bottom edges of the cube, enter a Pivot X
value of -1, a Pivot Z value of -1, and an Axis Z value of 90.
4.
In the Logic buttons, set Cube.001 to be a Dynamic Rigid Body actor. Leave Cube as it is. Generate a
simulation action by running the game engine with Record Animation. When you play back the anima-
tion, it should look something like
Figure 8-51
.
