How to create an oil rig.
By Stephane Dube

In this tutorial we will take a look at the following:
· How to offset a constraint
· To define rigid envelope within XSI
· To create a constraint using clusters.

1. Drag and drop Oil_rig.emdl into a viewport

2. Open a schematic view (short-key 9) and you will notice the hierarchy is already created, in the scene

3. You will need to create a 2D chain to create the piston effect for the engine of the rig

Expand the Right View port (F12)
-Animate>Create>Skeleton>Draw 2D Chain
Make sure you start the chain from the middle of the "arm" of the oil rig, and the effector is in the center of the small_bottom_handle



4. Select the first bone of the skeleton; you want to make it parent of the "arm rig" select the Parent command in the Main Control Panel (MCP) then middle click on the arm rig this will create a rigid envelop of the child hierarchy since the bone (the parent) will drive the entire branch hierarchy.

5. We will do the same thing for the Left and Right Handle. Branch select the Left Handle (Middle click on the Left_Handle) or type in B:left_handle in the Object Selection from the Main Control Panel

6. Once the branch left_handle is selected, select the Parent command from the MCP, then middle click on the bone. At this point; the Bone1 is the parent of the branch left handle. Right click to terminate. Branch select the the Right_handle and make the bone1 the parent of the Right_handle hierarchy. Once again this creates a rigid envelop since the bone1 is the parent of the entire hierarchy.

Next step animate the piston

7. Select the effector of the skeleton
Then select Animate>Create>Path>Set Path
Set these settings:
Start Frame:1
End Frame: 25
Check-mark linear this will prevent any acceleration or de-acceleration from the animation
Once all of the properties are set select the blue_circle.

Lets make the f-curve a constant cycle,
8. Select the Effector then open up the Animation Editor ( short-key: 0 ) select the only F-curve. In the curves menu select Curves>Cycle, this will generate a cycle of the f-curve to indefinite.

9. Play back the animation you will notice the following a) the drill does not follow the hammer_head this is due because the drill is not part of any hierarchy nor does it have any constraint. We will fix this at a later step. The next thing you will notice is the handles are a bit offset from the engine box we want to center both of the handles center to the engine box.

10. Select the effector and select the Comp from the MCP you will be able to move the effector around since the comp will create an automatic offset within the constraint of the path, however it will keep the circular animation (the path animation)

11. Create a Cluster constraint
Select the hammer_head and tag the middle vertex from the top of the opening (see figure.3) then from the MCP select cluster, this will create a local cluster within the hammer_head property

12. Select the drill, then from the MCP select Contraint>Object to cluster,
(Helpful tip; open up an Explorer ( 8 ) and press F to isolate the selection, open up the Polygon Mesh > Clusters> then select the point clusters from the Hammer_Head property.

13. You will notice the drill will go in the middle of the cluster this is because the center of the drill is in the middle of the geometry. When creating a constraint it will take the center of the object and constraint it to the cluster.

14. Once again, use the Comp command from the MCP and translate the drill. The drill should be inward of the hammer head.

15. Remove the Comp command and there you have it folks a simple oil rig.

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