Understanding Constraints Tutorial

By Ricardo Tobon

Page 3

Turning Constraints On and Off

Close the Basic_Constraint.fbx and open the On_Off_Constraints.fbx. In it you will see a similar scenario as the previous file, a sphere, a cube that moves left to right and a cone that moves upward. In addition, you will find a Position Constraint (Sphere_Cube_Position) and a Parent Constraint (Sphere_Cone_Parent) (fig 10).



Fig 10.

Double click on the Sphere_Cube_Position constraint to load its options under the Asset Settings area. Select the Sphere and Alt + drag it to the Constrained Object section under the Sphere_Cube_Position Constraint Settings. Select the cube and Alt + drag it to the Source 1 section. Figure 11 shows how the Sphere_Cube_Position Constraint Settings should look (fig 11).



Fig 11.

Click on the snap button to activate the constraint while leaving the original offset.
Double click on the Sphere_Cone_Parent constraint to load its options. Select the Sphere and Alt + drag it to the Constrained Object section. Select the cone and Alt + drag it to the Source 1 section. Figure 12 shows how the Sphere_Cone_Parent Constraint Settings should look (fig 12).



Fig 12.

Go to frame 45 and click on the snap button to activate the constraint (as discussed earlier, the relationship between the objects involved in a constraint is related to the distance between the objects at the time of activation).
Set key frames on the weight channels for both constraints by pressing the key button besides the weight channel in each of the constraint’s settings (fig 13).



Fig 13.

Follow the values on figure 14 to know the number to type for each constraint each time you set a key frame (fig 14).



Fig 14.

When you play the animation you will see the sphere move left to right from frame 0 to 45, then blend to the cone motion from 45 to 55 and move upwards from 55 to frame 100 as it also rotates, all these while always keeping the initial offset (mov 4).

 

 

Mov 04.

 

 
 

Plotting Constraints

By turning the sphere constraints into motion and rotation keyframes (plotting) you liberate the sphere to drive other objects like the cube or the cone without creating a cycle.
Select the sphere and go to the animation menu and select plot selected all properties, the default options will work fine, click Ok (fig 15).



Fig 15.

Delete both the Sphere_Cube_Position and the Sphere_Cone_Parent constraints by right clicking on them and selecting delete from the options. When you play the animation you will see that the sphere moves in the exact way as it did when the constraints existed.

Conclusion

Constraints are powerful tool that allow you to control an object with another object while filtering the transforms taken by the constrained object. They also allow for several source objects. Constraints can be turned on and off so an element can drive the relationship for part of the animation and another object can gain control at a different part of the timeline. Constraints can also be plotted so the information gets baked on the channel of the constrained object.  

 
   
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