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You should be familiar with the QuickTime Movie Toolbox, as documented in Inside Macintosh: QuickTime. It will also help if you are familiar with using the QuickTime VR Authoring Tool Suite to create object movies.

Note:

Although this file format will be supported in future versions of QuickTime VR, be aware that the object movie file format will change significantly in the next release.

• About the Object Movie File Format
  
• QuickTime VR Object Movie Authoring
  
• Summary
  

• an enabled video track containing the views of the object

• a 'NAVG' atom in the movie user data area describing the parameters of the object

• a 'ctyp' atom in the movie user data specifying the QuickTime VR object movie controller

• the poster time set to the poster view of the object

• the current time set to the poster time

• an optional movie file preview

The Movie File

As with any QuickTime file that is intended to be played on both platforms, a data fork version of the file should be created using the FlattenMovie Movie Toolbox call with the flattenAddMovieToDataFork flag set.

Movie Controller User Data

UserData uDat;
OSType controllerSubType = 'stna‘;
uDat = GetMovieUserData (newMovie);
SetUserDataItem (uDat, &controllerSubType, sizeof(controllerSubType),
			'ctyp', 1);

The Object Video Track

Figure 1 Camera postions to capture views of an object

Ordering the Frames - Simple Object

Your first shot at each horizontal position should be of the back of the object, so that the frame showing the front of the object is half-way through the series at that horizontal position. This improves disk-access time at run-time, since the user will most likely be looking at the front of the object.

Use the following procedure to shoot a full object which shows all possible views:

1. Position your camera with the vertical pan at 90deg. (directly above the object).

2. Shoot the first frame.

3. Keep the camera at the same vertical pan position and rotate it counter-clockwise to the next position by increasing the horizontal pan angle, then shoot the frame.

4. Repeat step 3 until you return to the starting point.
   If you moved the camera 10deg. between each frame, you should have 36 frames to capture the entire 360deg..

5. Move the camera down by reducing the vertical pan angle.

6. Repeat steps 2 through 4 for this vertical pan position.

7. Repeat step 6 for each vertical pan position until you reach a vertical pan position of -90deg. (directly below the object).

Save the resulting set of frames as PICT files in the form name.001, name.002, etc., and then convert the frames into a movie using a utility such as ConvertToMovie. Alternatively save the frames directly into a QuickTime file during capture. Each frame must be a key frame. Frame differencing (temporal compression) cannot be used for simple objects. Apple recommends using the Apple Video compressor for 16-bit or greater images and the Apple Graphics compressor for 8-bit images. Experiment with the compression quality to reduce the file size. Each frame must have the same duration. If you set the duration to about 1/10 of a second, you can play the movie as a QuickTime linear movie to verify that all frames were captured properly. The frame duration is inconsequential after conversion to QuickTime VR format.

Ordering the Frames - Looping Object

2. Shoot N frames of the animation loop.

Note:

You must shoot exactly N frames at each camera position. When converting the resulting frames to a movie, specify a key frame every N frames. This will reduce the file size by allowing for frame differencing in the animation loop. At minimum, the first frame of the animation loop at each camera position must be a key frame.

Interpreting the Frames of an Object Movie

Figure 2 Interpretation of the order of frames saved in a video track in relation to horizontal and vertical camera positions

Table 1 summarizes the information used during the capture process and the corresponding parameters required by the NAVG atom:

Table 1 Information used during the capture process

Frame Position			File format parameters	
Number of horizontal positions			# Columns	
Number of vertical positions			# Rows	
Starting H pan position (usually 0deg.)		Start H Pan	
Ending H pan position (usually 360deg.)		End H Pan	
Starting V pan position (usually 90deg.)	Start V Pan	
Ending V pan position (usually -90deg.)		End V Pan	
The N frames of the animation loop		Loop Size	

Note:

If the start and end H pans are exactly 0 and 360, frames in the horizontal dimensions are "wrapped," i.e., stepping past the last frame of a row will display the first frame of that row. There is no wrapping in the vertical direction.

Extending the Concept of an Object Movie

The `NAVG' User Data Atom

The 'NAVG' atom in the movie user data area contains the parameters of the object movie. The first user data item list contains the following data structure:

// File format for version 1.0.
#pragma options align=mac68k		// Use Macintosh 68k alignment
typedef struct {
	short	versionNumber;		// Always 1
	short	numberOfColumns;	// Number of columns in movie
	short	numberOfRows;		// Number rows in movie
	short	reserved1;		// Zero
	short	loopSize;		// Number of frames shot at each position
	short	frameDuration;		// The duration of each frame
	short	movieType;		// kStandardObject, kObjectInScene, or
					// kOldNavigableMovieScene
	short	loopTicks;		// Number of ticks before next frame of
					// loop is displayed
	Fixed	fieldOfView;		// 180.0 for kStandardObject or
					// kObjectInScene, actual degrees for
					// kOldNavigableMovieScene.
	Fixed	startHPan;		// Start horizontal pan angle in
					// degrees
	Fixed	endHPan;		// End horizontal pan angle in degrees
	Fixed	endVPan;		// End vertical pan angle in degrees
	Fixed	startVPan;		// Start vertical pan angle in degrees
	Fixed	initialHPan;		// Initial horizontal pan angle in
					// degrees (poster view)
	Fixed	initialVPan;		// Initial vertical pan angle in degrees
					// (poster view)
	long	reserved2;		// Zero
} QTVRObjectFileFormat1x0Record, *QTVRObjectFileFormat1x0Ptr;

Note:

In the above data structure , the sizes of the data types are:

Type		bit size

short		16

Fixed		32

The structure uses Macintosh 68K alignment.

enum {
	kStandardObject		= 1,	// "Object"in Add Object Data dialog
	kOldNavigableMovieScene	= 2,	// "Scene"in Add Object Data dialog
	kObjectInScene		= 3	// "Object In Scene" in Add Object
					// Data dialog
};

The loopSize parameter is 1 for a simple object and the number of frames, N, shot at each position for a looping movie. For a simple object, the loopTicks parameter is ignored. For a looping movie, a LoopTicks value of 0 indicates that the next frame at that position should be displayed as quickly as possible. If the value is greater than 0, the frames of the loop will be cycled at the constant rate specified (in 60ths of a second). Frames will be skipped to maintain the frame rate. If the value is negative, the next frame in the loop is show only after the absolute value of the specified time (in 60ths of a second) has elapsed. This ensures that every frame will be displayed in sequence.

The field of view parameter is 180 for standard object or an object in scene. For an old navigable movie of a scene, it is the approximate field of view of the image.

The parameters initialHPan and initialVPan specify the horizontal and vertical pan angle of the object's poster view. This view is displayed when the movie is first opened.

The Object Movie's Poster View

SetMovieTimeValue	(movie, posterViewTime);
SetMoviePosterTime	(movie, posterViewTime);
SetMoviePreviewTime	(movie, posterViewTime, frameDuration * loopSize);

Authoring a object movie file is a fairly simple process if you make sure there are the right number of frames in the video track, and if the duration of all frames are the same. Make sure the resulting file is verified using QTVRPlayer.

• Inside Macintosh: QuickTime

• "Generating QuickTime VR Movies from QuickDraw 3D," in develop Issue 25.

• QuickTime VR 1.0 Authoring Tool Suite manuals