Using the SplinMotion Plug-in to build an Animation Rig in Cinema 4D XL6

by Mark Simpson President, JAM Digital ©2001 Mark Simpson. All Rights Reserved. Used at CreativeCow.net by kind permission of the author.

Article Focus: This article will demonstrate how to set up the SplinMotion Plug-in to build an animation rig allowing you to animate a fire hose by moving only one null. The article will not focus on the modeling or texturing aspects of the project as they're really not important, but rather the rig used to animate the spline from which the firehose is formed. This principle can be used to animate any spline based model.

For this Project you will need the "SplinMotion" Plug-in Available from the Maxon Website
For this Project you will need Cinema 4D XL6
For this Project you will need the Project Files



Create the Animateable Spline and it's target Nulls

First, create a straight spline (object menu>create spline>B-Spline). Then click in the editor window (XZ plane) to set your first point, then move along the z axis in the positive Z direction, and set another point, move farther along the Z axis in the positive Z direction and set another point, then move farther yet along the Z Axis in the positive Z direction and set a fourth point. Hit the escape key (esc) to stop drawing points.

With the "points tool" selected, select the first point and then enter "0,0,0" in the coordinates window and click the "apply" button. Then select the second point, and enter "0,0,200" in the coordinates window and click "apply". Then select the third point and enter "0,0,800" in the coordinates window, and click "apply". Finally select the fourth point and enter "0,0,1000" in the coordinates window and click "apply". You should now have a straight spline with four points, one at each end, and one at 200 units in from each end.

Next create four null objects (Object Menu>Null Object). The first one position at "0,0,0" in the coordinates window (with the object tool selected) and rename it "Null Point 1". The second one position at "0,0,200" in the coordinates window (with the object tool selected) and rename it "Null Point 2". The third one position at "0,0,800" in the coordinates window (with the object tool selected) and rename it "Null Point 3". The fourth one position at "0,0,1000" in the coordinates window (with the object tool selected) and rename it "Null Point 4". You should now have a Null Object for each spline point, positioned in exactly the same place as each spline point.





Create the Firehose and place a control object on the end
Create a circle spline (Object Menu>Spline Primitive>Circle). Double click on it in the object window and set it's radius to 15 and ensure that it's orientation is in the XY plane. Select OK.

Create a Sweep NURBS object (Object Menu>NURBS>Sweep NURBS), and rename it "Firehose". Drag the Original Spine object into theSweep NURBS (Firehose) Object and then do the same for the Circle Spline. You should now have a cylinder, 20 units in diameter running the length of the spline object. If not, ensure that the circle and B-Spline Spline are both Children of the Firehose, and that the Circle is higher in the Hierarchy. Also ensure that the circle spline is oriented on the XY plane.

Create an object (a 40 x 30 x 30 cube will work) to be on the end of the "hose" and place it in a null. Create a Null and name it "Firehose/Cube" and place everything in the object window in it so that it is the parent object to everything else. You can also do this by hitting the "G" key (with the object window active), and dragging a marquee to select all the items in the object window. You should now have the Firehose with a cube placed on the end of it at "0,0,0".





Apply the SplinMotion Plugin and edit the Expression to Target the Nulls
Select the "Spline" Object in the Object window (It should now be a child of the "Firehose" Object), and apply the "SplinMotion" Plug-in (Plugins Menu>set SplinMotion-Object). Select OK in the Dialog that appears. A new object group should appear in the Object Window called "Spline [SplinMotion]". Open this group (click on the box with the "+" in it), and there should be another group labeled "Spline [0-3]" with a SplinMotion Tag applied to it. Open this group and there should now be four nulls (one for each point on the Spline that the plug-in is applied to). Understand that once the plug-in has been applied, the points on the spline can no longer be moved, so if you need to adjust them, you will have to delete the SplinMotion Group first, edit the spline points, and then reapply the plug-in.

Select the "Spline [0]" null (in the SplinMotion group), and apply a C.O.F.F.E.E. Expression (Object Window>File Menu>NewExpression>C.O.F.F.E.E. Expression). A coffee cup Tag should appear next to the selceted null in the Object Window. Double Click on this Tag and the C.O.F.F.E.E. Expression Editor Window should open. Click on the 'Load' Button and select the "FirehoseEXP.txt" file that is downloadable via the links at the beginning of this tutorial.

Duplicate the coffee tag for each of the remaining nulls in the "Spline [0-3]" group. Then with the Expressions Editor Window Still open, select each icon and rename the target in the expressions editor so that they successively point to each Null Point we created for our Spline Points. So when you are done, The Coffee tag for "Spline [0]" should target "Null Point 1", the Coffee tag for "Spline [1]" should target "Null Point 2", the Coffee tag for "Spline [2]" should target "Null Point 3", and the Coffee tag for "Spline [3]" should target "Null Point 4".

Next Drag the "Null Point 2" Object onto the "Move Me" Object so that it becomes it's child, then do the same for the Null Point 1" object.

Finally Duplicate the coffee tag again for the "cube" object. In the coffee expression Editor, edit the code (in the same place as above) so that the expression targets teh "Spline [0]" object. By targeting the SplinMotion Object this way, any lag in movement of the spline will be translated to the cube object so that they are always locked together perfectly.





Animate the Hose
Now, with the object tool selected, and the "Move Me" Null highlighted in the Object Window, move the "Move Me" object by using either the move tools or by entering coordinates in the coordinates window. The hose should now remain attached to the cube as it moves, even when the direction is changed.





Congratulations, you've just built a SplinMotion animation rig. Now all that remains is to keyframe the positions of the "Move Me" object, and render your animation.

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