by
Al Street
© 2002
Al Street. All Rights Reserved.
Overview: Does this apply to you? You're interested in motion tracking some footage, and you're on a budget. You own LightWave, but don't have a lot to spend on a compositing application. Maybe you own the Standard version of After Effects, but haven't sprung for the Production bundle upgrade yet. Or maybe you're a purist, who tries to do everything possible inside good old LightWave. Well, read on! We will delve outside of LW for this, but it won't cost much and you'll get an excellent reference on compositing in the bargain. Doug Kelly has written an excellent book, Digital Compositing in Depth, ISBN 1-57610-431-1. List price is US $49.99, but I've seen it on Amazon for as low as $21.85 used. Included on the first of two CDs that come with the book is a demo version of Digital Fusion version 2.52 (Note: You can also get version 4 of the Digital Fusion demo online from eyeon Software). This is a fully-functional demo that is protected by watermarks on the output image. You can save files, including the output of the motion tracker, which is in a modified LW motion file format. (I say modified but the data is actually normalized, where the center of the image is at x,y = 0.5, 0.5 and the maximum extents (lower right) is at 1,1). For DF versions 3.12 or 4, Eyeon has changed their version of the LW .mot format so we'll use their polyline format (.dfmo) instead. We'll track some footage in Digital Fusion (Evaluation version), then load the tracker keyframes into LightWave. We'll also convert the data to a format that can be pasted into After Effects. |
In Digital Fusion
Refer to the book and/or help files for information on using Digital Fusion.
Add a Loader to the flow and import your footage. Add a tracker to the output of the flow as shown. **DF 3 or 4: Go to File > Preferences > Frame Format and make Aspect Ratio = 1 : 1.
Changing this setting will affect the tracker data exported! (Changing this setting in DF2.52 has no effect on the exported data) Click on the Tracker 1 tile in the flow, then set your feature region and search region in the main display. In the Tracker 1 control panel, choose Select Pattern. Make sure you have Render Start and Render End (at the bottom of the flow) set to the frame range that you want to track, then click on Create Path. When the tracking operation is complete, right-click on the path in the main display, choose "Path 1 > Export Path > LightWave MOT..." and give the file a name.
Change the default ".mot" extension to something else or it will be
overwritten in a later step. (I used ".mo5" because it is a modified
LW 5 motion file.) **DF 3 or 4: When you are ready to export the tracked data, right-click on the path
and select Path 1 > Export > and make sure that "Key Points" and "Absolute" are checked, then select "Motion Path" and save the data as a Polyline File
(dfmo extension). A motion file will be created.
In LightWave
Add a null and name it "Tracker_Null." In the Image Editor, Load the footage that you tracked. Under the Scene tab, choose Compositing and set your loaded footage as the Background Image. In the Display panel, make sure that Camera View Background is set to Background Image. Run TransMotion3D and choose the tracker file as the Input File (ours was
zoom_car.mo5). Check Load Motion to Selected Item (which should be "Tracker_Null"), check Activate AutoCamera, and make sure that Ref. Image has your
Background Image or sequence selected. Click on Ok. **DF 3 or 4: Select "Digital Fusion 3.x - 4.x DFMO" for the Input
Format in TransMotion3D. The plugin creates a new camera and you are prompted to give it a name. Just hit enter; the plugin will rename the new camera "HelperCam." In the Camera viewport you should see your tracked footage with "Tracker_Null" positioned at the proper location. Hit the ] key a few times to increase the grid size, and you should see four nulls framing the view. These are just there as a quick check that everything is set up properly. If your goal was to get the tracked footage into LightWave, you're ready to go. If you want to bring the tracker keyframes into After Effects, do the following: Run transMotion3D and select "zoom_car.mot" as the Input File.
This is the motion file saved by the plugin from the original
"zoom_car.mo5" file. Make selections as shown in the figure below. Make sure that you set Pixel Aspect Ratio (PAR) to that of the footage that you have loaded into After Effects>. After Effects modifies the input data based on the PAR setting of the composition. Click Ok and the file "zoom_car.aek" will be created. In Notepad, open the file "zoom_car.aek", Select All and Copy to the clipboard.
In After Effects
Create a small solid layer (I used 20x20 pixels) to accept the keyframes. Select the layer and paste in the keyframes. Note that the keyframes match the feature tracked in the footage layer. You've tracked the motion in one application (Digital Fusion), and brought the tracked data in to two other applications (LightWave and After Effects).
