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Introduction

In this tutorial, we're going to create an animation of an object suspended from a track. The hanging object will move along the track, while conforming to the shape. This is diffucult, if not impossible in many applications, but can be done very easily with Pixels' basic path tools.

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Step 1: Start with the Splines

First, enable Snap to Grid. This will make it easier to line up the points of the spline.

We'll start by creating a B-Spline that will serve as a path for the 'hanger'.

Draw a spline similar to the one shown. Note the curvature of the actual spline in relation to the hull. We want a path in the shape of the hull, but non-linear, because, linear is ugly.

With the spline selected, go to the Scripts Menu, and select the DoubleU4Extrusion.tcl script.

Suddenly, the Spline sharpens, but with nice, smooth edges. It does this by doubling each point of the spline, excluding the last, which in turn, increases the tension on those points.

Draw a second spline with 4 points. It will look circular.

Run the DoubleU.tcl script to sharpen the edges. This doubles every point of the spline.

Step 2: Create the Hanger

With the square spline still selected, shift-select the original path. Choose Shape>Path Extrude.

It should now look something like the image on the right.

And the Camera view....

Now, we'll close the ends of the hanger with a sharp edge.

Lock it. This keeps it out of the way while we construct the track.

Step 3: Create the Track

Using the locked 'hanger' as a guide, draw a spline in the shape of the track that will support it. Once again, consider the hull, not the curvature of the spline.

Name it Track_Profile.

With the spline selected, run the DoubleU4Extrusion script.

That's it for profile splines, so we can disable Snap To Grid.

In the Top View, draw a closed spline. The shape doesn't matter. Make sure the curves are not too narrow. Once it is drawn, using the move tool, raise it off the 'ground' along the Y axis.

Name it Track_Path.

This spline will serve a dual purpose. It will serve as the path for an extrusion, as well as the motion path for the 'hanger' object.

When preparing path animations, it is best to Re-Order the path spline uniformly. This ensures the motion flows at a consistent rate.

Select Track_Profile, then Shift-Select Track_Path. Choose Shape>Path Extrude.

You should now have a track object that looks something like this.

Name this object 'Track'

While the Track is selected, change the U Subdivisions from 8 to 2. This will greatly decrease redraw & render time. While we're here, lock the Track.

Now we need to work with the original Track_Path Spline. Select it with the Popup Menu in the Object Info Palette, and Unlock it.

Step 4: Animate the Hanger Along the Path

Select Hanger, and Shift-Select Track_Path.

Choose Control>Path/Unpath, and enter the range 0 to 240. The hanger object now moves around the track, but it doesn't take rotation into account.

Create a Null, and name it 'Target'. With Target selected, Shift-Select Track_Path, and choose Control>Path/Unpath again. This time enter the range -2 to 238. This places the Null 2 frames in front of the Hanger for the duration of the animation.

Now, to automatically rotate the hanger to conform to the path, select the Hanger, and Shift-Select the Target.

Choose Control>Look/Unlook

The Hanger snaps into alignment with the track. And now....to the TimeLine!

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Step 5: Adjust the FCurves

A little probing reveals the f-curve for the position on the Track_Path. Notice, it is not straight, but wavy. This means the motion will start slowly, speed up, then slow down again.

This is undesirable for the effect we're going for, so we'll have to linearize the path keyframes.

In blocking mode, select the keyframes for Hanger & Target. Click the linearize button ( the sawtooth shape ). Now the motion will be consistent throughout the animation.

Switching back to F-Curve mode, notice the temporal spline is straight.

Finished!

Find a good camera angle, and do a pencil test to see what you've accomplished in a few simple steps.