Tutorial - Converting Mirrorball

Converting a Mirrorball Image to a QuickTime VR Movie

This tutorial shows how to convert a "mirrorball" (a photograph of a reflective sphere) into a cubic format QuickTime VR movie. (If you would like to follow along with this tutorial, you can use the "sample mirrorball.jpg" file included in the download.)

Introduction

"Mirrorballs" are spheres with a mirrored surface that reflect the scene around them. They can take several forms, the most common and inexpensive of which are Christmas ornaments or "Victorian Gazing Balls" occasionally used in gardens.

Mirrorballs have the interesting optical property of reflecting almost all of a 360° scene apart from a hole directly opposite the camera. For the purposes of QuickTime VR, this means that quick & dirty panoramas can be created with just a single-shot.

By "quick & dirty" of course we mean that the resulting panoramas are unlikely to substitute for a quality stitched panorama. However, they may have their uses if a mirrorball with reasonably clear and defect free surface can be found. The mirrorball used for this tutorial image was bought from a garden center for $7.

It has a few bumbs on its surface but produces a tolerable image. For this tutorial, the mirrorball was suspended from the ceiling of a room, with the camera placed directly under it and triggered by self-timer.

Step 1

Drop the "sample mirrorball.jpg" image into the empty conversion area.

When CubicConverter detects the photo as a mirrorball, the image will be displayed with two circles superimposed over it. The inner circle determines the field of view (or how large the "hole" opposite the camera should be), while the outer circle indicates where it will be cropped when the conversion is begun.

Also shown is the info panel on the right with the rotation control revealed. As the tutorial photo has the camera directly underneath the mirrorball, the rotation can stay at 0°. (If the camera was pointing at a different place however, the rotation control could be used to compensate - see comment at the end of this tutorial.)

Step 2

Drag anywhere inside the outer circle to position it more centrally over the mirrorball.

For the tutorial image this means dragging it to the right.

If necessary, use the blue knob on the right side of the outer circle to expand or contract the circle to match the mirrorball.

Step 3

To begin the conversion, click the "Convert" button at the bottom of the window.

As with conversions of equirectangular or cylindrical images, you will see the six cube faces appear as they are processed. When complete, you will be taken to the Movie area to preview the result.

If you look closely, you can see where the distortions of the cheaply manufactured mirrorball impact on the mathematically determined positions for points in the panorama. Other parts of the panorama are okay. Allowing for the compromised quality, the creation of this VR movie has taken very little effort and no stitching whatsoever.

You can now proceed to save the movie to disk.

Further Information

The sample image in this tutorial was photographed with the camera directly underneath the mirrorball (see photo in introduction above). As a result, no rotation was required. For images where the camera is not underneath the camera, you will need to adjust the rotation control to compensate.

Detecting Mirrorball Images

As images containing photographs of mirrorballs are just regular TIFF or JPEG images, CubicConverter must make some assumptions about the image in order to determine that it contains a mirrorball and that the appropriate controls should be shown.

By default, the assumption is that if an imported image is in the aspect ratio typical of a digical camera, then it is probably a mirrorball and not an existing panorama (either 2:1 for equirectangular, or some other ratio for cylindrical).

If this assumption does not match your digital camera, you can change it in the Preferences in the "Importing Images" area.

Watch Movie of Tutorial Being Performed  [0:23]

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