Max-Animation | Voodoo Camera Tracker Tutorial

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Voodoo Camera Tracker Tutorial:

Part 1 - Quickstart	Back to Max-Realms.Com
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Part 2 - Creating .tga sequence in 3ds Max
Part 3 - Importing the Camera data into 3ds Max
Part 4 - Adjusting your 3d scene to the voodoo_cam

Part 1 - Quickstart

Start by opening the Voodoo Camera Tracker program. By default, the software opens as two windows: One is the main window and the other is a notice/warning display window. To make things easier, arrange the windows similarly to what you see here:

The first thing you need to do is to load an image sequence into the Voodoo Camera Tracker. For now, Windows users may only import a .tga sequence. If you have 3ds Max, you can convert your video footage to a tga sequence by assigning the video as your background and rendering out to a .tga sequence. You can even lower the resolution by 1/2 if you're planning to use the tga sequence as the actual background in your 3ds Max scene. If you plan to use the original video for you scene, but still want to lower the resolution for Voodoo Camera Tracker, just make sure the frame rate is the same for both. For example, when you output a tga sequence using 3ds Max, the frame rate will be 30fps but your original footage was probably captured at 29.97. You'll need either convert the original footage to 30fps or render out a new tga sequence at full resolution and 30fps for your scene. Either way it doesn't matter if the resolution you use in Voodoo Camera Tracker is full or half because the exported MaxScript contains camera position and rotation data. It doesn't care if the background is 360x240 or 720x480 just so long as the difference is proportionate. Action: File>Load>Sequence

Once the file location window pops up, click on the first numbered image in the sequence, ie. image000.tga, and click Open.

In the next window, se the start and end frames (if you want to do only part of the sequence) and then choose the Rotation type. See the chart below for suggested uses.

Note: Even with interlaced video, I've always used "Not Interlaced" and have gotten good results. It may be because the image resolution is low.

Next, set up the Initial Camera:

Action: File>Load>Initial Camera

The most important setting here is Film Back. For 360x240, the film back is 3.24

If your image resolution is different than this and you know your aspect ratio and pixel ratio, just enter numbers into the Film Back window until the readouts correspond correctly. To find out your aspect ratio and pixel ratio in 3ds Max, load the video file as the background and hit the Render button. The Render dialogue will tell you these ratios.

You're now ready to begin your first track. We purposely don't adjust any other parameters at this time because we need a benchmark first. And since Voodoo Camera Tracker is inherently accurate, most times you don't need to adjust anything anyway.

Action: Click the Track Button

Voodoo Camera Tracker begins tracking each frame one-at-a-time. This is unless you have set the Step value higher than the default of "1".

Watch the Notice window for any warnings. You should see the phrase "Successful" on each frame. If you see "Failed" it's okay if it only happens 1 or 2 times in a long sequence.

At the end of a successful track, the Notice window will display the Final Estimate RMSE values. This is the mean error for the entire track. The lower this number, the better.

If the RMSE error is high, you will be asked to do a bundle adjustment. Look at the error value, though. If this value is less than .6, you probably have a pretty good track. You can click YES to the question, but be prepared to wait a very long time if your step is "1" and you've tracked several frames. See the Tips/Tricks for more information on this subject.

If you had a good track or even one like in the last part, you're now ready to export your script to your 3d application of choice.

Action: File>Save>[choice]

General Tips/Tricks

(1) Windows User: You can ONLY use a .tga sequence for now.If you have 3ds Max, you can load your .avi or .mov as the background, set the resolution proportionately, and render out to a .tga sequence

(2) Film Back: Your .tga image resolution is the key here. For example, if your .tga image resolution is 360x240, then your aspect ratio is 1:35 and your pixel aspect ratio is .9. So, you need to set your film back to 3.24

To make it easy (in 3ds max) just go to the render dialogue and see what the aspect ratio and pixel ratios are for your resolution. Then in Voodoo, enter numbers in the Film Back slot until the ratios are reading correctly.

(3) User Fixed and Constant focal lengths are for Free Move. Variable focal length is for Tripod. However, if you film Free Move with a zoom, you'll need to use Tripod/Variable or you'll pull your hair out. Example Video (6MB): Free Move - Zoom Video

(4) If you are tracking Free Move with User Fixed and the notice dialogue states that it cannot find a "valid keyframe", then you need to change keyframes to "manual" in the Free Move widget

(5) When tracking Free Move, watch the notices for individual RMSE values exceeding .2 - You will usually get a bad track if this is the case. The Final RMSE error can be above .2 as this is the final mean error. Note: This does not apply to Tripod movement type.

(6) Bundle Adjustments: If you set up Voodoo correctly to begin with, you don't need to do this. I haven't needed to yet and when I've tried, the results were horrible and took several hours to complete. In this example, the tracker reported "high errors" and asked if I wanted to do a bundle adjustment. The RMSE was .5 however, so I went with it. As you can see, it worked just fine without the adjustment: Free Move - Pan Video :: Cropped Version

(7) Go with the defaults BEFORE you mess with options. I've found that even the most complex shot tracked best with default options and MINOR tweaking. For the most part, if you're using Free Move, just set the Film Back correctly and you'll be okay. If you're using Tripod, then set the film back and relax. Tripod is very forgiving.

(8) Manual Keyframes: Although it makes sense to set a keyframe every frame (and is often needed when doing a Free Move track), this can really mess up a Tripod shot for some reason. Like I said before, try the defaults first.

(9) The export script puts the camera at 0,0,0 in position and rotation (unless you change this before tracking in the Initial Camera's "Position" widget) - In 3ds Max you can make a dummy object and move it to 0,0,0. Then link the camera and all of the feature point helpers to the dummy. Now you can move, scale and rotate the dummy to orient your scene.

(10) Free Move results in a 3d representation of your scene. Tripod results in a 2d representation. (look at the feature point helpers within your scene after running the import script and you'll see what I mean) - So, when placing your 3d objects in relation to the voodoo_cam, you'll need to pay close attention to scale if the tracking was Free Move. You may think the tracking was bad because the objects "move" around the scene while rendering. The scale is probably just off in the 3d environment. If the tracking was Tripod, then this is not so critical since it is 2d, ie. no depth was taken into consideration.

(11) Final Estimation Bundle Adjustments: Just because the Bundle Adjustment window pops up at the end, doesn't mean your track is unusable. I normally can track a pan (Tripod type) shot without the bundle adjustment window popping up. Occasionally when I'm using Tripod type for a Free Move pan, this will happen. Generally, the track is good enough depending on your scene and how static your 3d objects will be in your scene. When the window pops up, look at the Notice window. The Final Estimation RMSE error will tell you if it's good enough. If the amount is below .6, then you can probably use the track. Just export the script and give it a shot before trying again.

The information on the chart below are just suggestions when starting a new track. They are by no means the exact way every shot should be handled. These are the combinations which have given me the greatest success thus far.

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Voodoo Camera Tracker Tutorial: