3D Rotation from Video

A common use for HotMedia is the creation of a virtual 3D experience by extracting frames from a video taken of a rotating object.

One of many possible procedures for creating a HotMedia of a 3D rotation is:

  1. Video an object rotating.
  2. Capture the video to an authoring package of your choice.
  3. Crop the video to the area of interest (frequently some turntable, etc. may be visible in the background).
  4. Render frames from the video individually. Eventually they need to be in JPEG or GIF format -- most likely JPEG for video material.
  5. Create a HotMedia.

This example uses a toy car video on a small rotating platform. The initial sequence was captured at 15 fps at a resolution of 352x240...

The next step is the cropping to the area of interest...

Finally, the video is reduced in size...

Now, the choice of the number of frames is a tough one. Rendering 'all' the frames may yield 80 frames for one rotation of the car. Even at about 2K per image (136x56 images in this example are about 2K each) you would end up with a HotMedia that would be over 100K.

Many developers have a maximum size they want for each HotMedia experience they are creating. For this example, we will target 40K, which means we will end up with about 20 or so images. Through experience or experimentation, one way to create an image set that will meet this criteria is to 'render' the image frames from your video editing package of choice at differing frame rates such that the resultant number of frames meets the frames*frame_size criteria.

Click to start!

78 frames 33ms delay 114K
27 frames 150ms delay 40K

Note: The rate at which the files are loaded the first time is limited by the network, so until the cars complete one revolution, the timing may appear off. To best compare these HotMedia objects, let the cars spin one revolution, then click to start and stop them. Also click and drag for comparison.


The lesson is that you need to build HotMedia objects with image sets extracted from videos at different frame rates, or be selective in the images placed in the HotMedia.