QuickTime VR Authoring Tricks

Directory

How-to

• Applying an alpha-masked overlay to a QuickTime VR panorama

Panorama Resolution

• How to determine resolution of a panorama.

Calculators

• Determining the field of view from the lens focal length
• Determining the zoom ratio corresponding to 1:1 zooming
• Determining tilt limits for asymmetrical panoramas
• Determining panorama pan and tilt ranges
• Determining the number of photographs necessary to achieve the desired overlap
• Cropping
• Determining the tilt range for uncorrected panoramas
• Field of View from EXIF Data

Tools

• DeJitter
• DeFish - for dewarping fisheyes
• sizimg - command-line tool for batch resizing of images
• Loosen FOV limitations in QuickTime VR Authoring Studio

Open Source

• My open source repository - computer graphics and QuickTime VR

Applying an Alpha-Masked Overlay to a QuickTime VR Panorama

It may sometimes be desired to have an overlay on top of a panorama. This is a relatively simple procedure using QuickTime Player Pro. Although there are many steps, subsets of these steps are idioms used when editing arbitrary QuickTime VR movies, and are useful to learn. The basic process is:

1. Open PhotoShop.
2. Make a new image the size of the QTVR Window.
3. Add an alpha channel, and paint it as your mask.
4. Color the RGB any way that you want.
5. Save as a PhotoShop document.
6. Open the PhotoShop mask file as an image sequence in QuickTime Player.
7. Select All (cmd-A).
8. Copy (cmd-C).
9. Open up the QTVR movie.
10. Get Info (cmd-I).
11. Select "Controller" from the right info pull-down menu.
12. Select "Movie Controller" in the list.
13. Click on the QTVR movie window.
14. Select All (cmd-A).
15. Add Scaled (cmd-opt-shft-V).
16. Click on the "Get Info" window.
17. Select Video Track 2 (or whatever track you just added) from the left info menu.
18. Select "Graphics Mode" from the right info menu.
19. Select "Straight Alpha" from the list.
20. Select "Movie" from the left info menu.
21. Select "Controller" from the right info menu.
22. Select "QTVR Controller" from the list.
23. Click on the QTVR window and verify that the mask works.
24. Save As... Self contained.

Such a movie is necessarily slower to render than a straight QuickTime VR panorama, for several reasons:

1. Composition: the overlay needs to be composited with the rendered panorama;
2. Extra copy: an intermediate buffer is required to composite the overlay with the composited panorama, followed by a copy to the screen, rather than rendering directly to the screen;
3. Many pixels: potentially all of the pixels of the overlay need to be composited with all of the pixels in the panorama view, even those that are fully transparent;

The composition process can be made a bit faster by using a different transfer mode other than straight alpha. Premultiplied white alpha is faster, and premultiplied black alpha is even faster. If you can deal with the jaggies, transparent (chromakey) may be faster still on some machines. I personally prefer premultiplied black alpha. To convert a straight alpha image to a premultiplied black alpha image, do the following in PhotoShop:

1. Image > Apply Image
2. channel alpha (or whatever you called the fourth channel)
3. target RGB
4. multiply

This simply scales the RGB channels by the alpha channel. Of course, if your overlay is thusly specified, you would then choose "premul black alpha" in the graphics mode menu in QuickTime Player Pro. In versions of PhotoShop prior to 5.5, you may need to scale each channel separately.

Unfortunately, there's not much you can do about speeding up the extra copy, although you might see a barely noticeable speed improvement if your window is aligned appropriately (as provided by QuickTime Player, but not the browser plug-in), and the window is a multiple of four pixels in width.

Certain situations can decrease the number of pixels involved in the composition. For example, if you merely want to overlay a small logo in the corner of the window, you can make the overlay image merely the size of the logo, then use the "Size" menu item in QuickTime Player's info window to position the logo appropriately. This would then make the composition time negligible.

DeJitter

DeJitter is a standalone application for removing jitter from a sequence of frames. It takes as input and provides as output either a linear movie or a set of image files. This runs on the Macintosh from system 8.6 to the latest OS X.

Download DeJitter

DeFish

DeFish is an easy-to-use application for dewarping fisheye images. It can create planar, cubic, and cylindrical output images. This runs on the Macintosh from system 8.6 to the latest OS X.

Go to DeFish page.

(If you are using Safari Beta and have download problems, try Explorer or Navigator).

Increase QuickTime VR Authoring Studio Lens FOV

The enclosed unofficial patch to QuickTime VR Authoring studio allows you to loosen up the restrictions on the vertical FOV of a lens to 160° instead of 130°. Make sure that:

1. You have applied the 1.0.1 upgrade to QTVRAS.
2. You have made a copy of this QTVRAS, and have archived it. Other patches will not work with this one installed.

Download the patch to QuickTime VR Authoring Studio to increase the limitations on FOV for lens specifications.