Camera racking (sometimes also called 'motion tracking') allows you to incorporate Blender objects into real-world video in which the camera was moving. In order for Blender to do this correctly it has to be able to analyze the real-world video to figure out exactly how the real-world camera moved so that the motion of the virtual (Blender) camera can be synchronized with the motion of the real camera. Blender does this by analyzing the apparent motion of at least 8 selected points in the real-world video. Selecting high contrast points that Blender can follow (track) easily is a key step to efficient camera-tracking, as you will see...
Warning: camera tracking can be a time-consuming process if Blender is unable to track without a lot of help from you, as usually seems to be the case. You can improve your chances of good tracking by using very quality footage in which the picture is sharp and not blurred by too-rapid motion of the camera.
Note that two kinds of camera motion can be used:
- panning video, made with a camera on a tripod which rotates but has no translational motion and thus no parallax change for the markers and no possibility of Blender to analyze the markers to obtain full information about their position in 3d space. Filming from a tripod does not give much sense of depth so use the other method if possible.
- camera motion that has not only rotation but also translation. In this case the translation motion must be significant so that Blender can analyze properly. In other words you MUST move the camera significantly backwards and forwards or sideways so that there is sufficient change in the relative positions of the markers for Blender to determine their relative position in 3D space.
Here are a few great, recent videos to get you started...
- I made this Vimeo video (40 minutes) about camera tracking but it's not the best, so check out instead one of the following:
- This 20 minute YouTube video is the first of two videos about camera tracking by CGBoorman.
- This 56 minute YouTube video is very good.
- This 60 minute YouTube video is the first of three advanced videos by CG Cookie in which a safe is modeled and textured and then made to appear to rise up out of a desk using camera tracking. The other two are 30 minutes each.