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Node Information Atom Container

The node information atom container includes general information about the node such as the node’s type, ID, and name. The node information atom container also contains the list of hot spot atoms for the node. A QuickTime VR movie contains one node information atom container for each node in the file. The routine QTVRGetNodeInfo allows you to obtain the node information atom container for the current node or for any other node in the movie.

Figure 3-17 shows the structure of the node information atom container.

Figure 3-17  Structure of the node information atom container

In this section:

Node Header Atom Structure
Hot Spot Parent Atom
Hot Spot Information Atom
Specific Information Atoms
Link Hot Spot Atom

Node Header Atom Structure

A node header atom is a leaf atom that describes the type and ID of a node, as well as other information about the node. Its atom type is kQTVRNodeHeaderAtomType ('ndhd').

The structure of a node header atom is defined by the QTVRNodeHeaderAtom data type:

typedef struct VRNodeHeaderAtom {

    UInt16                              majorVersion;

    UInt16                              minorVersion;

    OSType                              nodeType;

    QTAtomID                            nodeID;

    QTAtomID                            nameAtomID;

    QTAtomID                            commentAtomID;

    UInt32                              reserved1;

    UInt32                              reserved2;

} VRNodeHeaderAtom, *VRNodeHeaderAtomPtr;

Field descriptions

majorVersion

The major version number of the file format.

minorVersion

The minor version number of the file format.

nodeType

The node type. This field should contain either kQTVRPanoramaType or kQTVRObjectType.

nodeID

The node ID.

nameAtomID

The ID of the string atom that contains the name of the node. This atom should be a sibling of the node header atom. The value of this field is 0 if no name string atom exists.

commentAtomID

The ID of the string atom that contains a comment for the node. This atom should be a sibling of the node header atom. The value of this field is 0 if no comment string atom exists.

reserved1

Reserved. This field must be 0.

reserved2

Reserved. This field must be 0.

Hot Spot Parent Atom

The hot spot parent atom is the parent for all hot spot atoms for the node. The atom type of the hot spot parent atom is kQTVRHotSpotParentAtomType ('hspa') and the atom type of the each hot spot atom is kQTVRHotSpotAtomType ('hots'). The atom ID of each hot spot atom is the hot spot ID for the corresponding hot spot. The hot spot ID is determined by its color index value as it is stored in the hot spot image track.

The hot spot track is an 8-bit video track that contains color information that indicates hot spots. For more information, refer to Programming With QuickTime VR.

Each hot spot atom is the parent of a number of atoms that contain information about each hot spot.

Hot Spot Information Atom

The hot spot information atom contains general information about a hot spot. Its atom type is kQTVRHotSpotInfoAtomType ('hsin'). Every hot spot atom should have a hot spot information atom as a child.

The structure of a hot spot information atom is defined by the QTVRHotSpotInfoAtom data type:

typedef struct VRHotSpotInfoAtom {

    UInt16                              majorVersion;

    UInt16                              minorVersion;

    OSType                              hotSpotType;

    QTAtomID                            nameAtomID;

    QTAtomID                            commentAtomID;

    SInt32                              cursorID[3];

    Float32                             bestPan;

    Float32                             bestTilt;

    Float32                             bestFOV;

    FloatPoint                          bestViewCenter;

    Rect                                hotSpotRect;

    UInt32                              flags;

    UInt32                              reserved1;

    UInt32                              reserved2;

} VRHotSpotInfoAtom, *QTVRHotSpotInfoAtomPtr;

Field descriptions

majorVersion

The major version number of the file format.

minorVersion

The minor version number of the file format.

hotSpotType

The hot spot type. This type specifies which other information atoms—if any—are siblings to this one. QuickTime VR recognizes three types: kQTVRHotSpotLinkType, kQTVRHotSpotURLType, and kQTVRHotSpotUndefinedType.

nameAtomID

The ID of the string atom that contains the name of the hot spot. This atom should be a sibling of the hot spot information atom. This string is displayed in the QuickTime VR controller bar when the mouse is moved over the hot spot.

commentAtomID

The ID of the string atom that contains a comment for the hot spot. This atom should be a sibling of the hot spot information atom. The value of this field is 0 if no comment string atom exists.

cursorID

An array of three IDs for custom hot spot cursors (that is, cursors that override the default hot spot cursors provided by QuickTime VR). The first ID (cursorID[0]) specifies the cursor that is displayed when it is in the hot spot. The second ID (cursorID[1]) specifies the cursor that is displayed when it is in the hot spot and the mouse button is down. The third ID (cursorID[2]) specifies the cursor that is displayed when it is in the hot spot and the mouse button is released. To retain the default cursor for any of these operations, set the corresponding cursor ID to 0. Custom cursors should be stored in the VR world atom container, as described in “VR World Atom Container.”

bestPan

The best pan angle for viewing this hot spot.

bestTilt

The best tilt angle for viewing this hot spot.

bestFOV

The best field of view for viewing this hot spot.

bestViewCenter

The best view center for viewing this hot spot; applies only to object nodes.

hotSpotRect

The boundary box for this hot spot, specified as the number of pixels in full panoramic space. This field is valid only for panoramic nodes.

flags

A set of hot spot flags. This field is unused.

reserved1

Reserved. This field must be 0.

reserved2

Reserved. This field must be 0.

Specific Information Atoms

Depending on the value of the hotSpotType field in the hot spot info atom there may also be a type specific information atom. The atom type of the type-specific atom is the hot spot type.

Link Hot Spot Atom

The link hot spot atom specifies information for hot spots of type kQTVRHotSpotLinkType ('link'). Its atom type is thus 'link'. The link hot spot atom contains specific information about a link hot spot.

The structure of a link hot spot atom is defined by the QTVRLinkHotSpotAtom data type:

typedef struct VRLinkHotSpotAtom {

    UInt16                              majorVersion;

    UInt16                              minorVersion;

    UInt32                              toNodeID;

    UInt32                              fromValidFlags;

    Float32                             fromPan;

    Float32                             fromTilt;

    Float32                             fromFOV;

    FloatPoint                          fromViewCenter;

    UInt32                              toValidFlags;

    Float32                             toPan;

    Float32                             toTilt;

    Float32                             toFOV;

    FloatPoint                          toViewCenter;

    Float32                             distance;

    UInt32                              flags;

    UInt32                              reserved1;

    UInt32                              reserved2;

} VRLinkHotSpotAtom, *VRLinkHotSpotAtomPtr;

Field descriptions

majorVersion

The major version number of the file format.

minorVersion

The minor version number of the file format.

toNodeID

The ID of the destination node (that is, the node to which this hot spot is linked).

fromValidFlags

A set of flags that indicate which source node view settings are valid.

fromPan

The preferred from-pan angle at the source node (that is, the node containing the hot spot).

fromTilt

The preferred from-tilt angle at the source node.

fromFOV

The preferred from-field of view at the source node.

fromViewCenter

The preferred from-view center at the source node.

toValidFlags

A set of flags that indicate which destination node view settings are valid.

toPan

The pan angle to use when displaying the destination node.

toTilt

The tilt angle to use when displaying the destination node.

toFOV

The field of view to use when displaying the destination node.

toViewCenter

The view center to use when displaying the destination node.

distance

The distance between the source node and the destination node.

flags

A set of link hot spot flags. This field is unused and should be set to 0.

reserved1

Reserved. This field must be 0.

reserved2

Reserved. This field must be 0.

Certain fields in the link hot spot atom are not used by QuickTime VR. The fromValidFlags field is generally set to 0 and the other from fields are not used. However, these fields could be quite useful if you have created a transition movie from one node to another. The from angles can be used to swing the current view of the source node to align with the first frame of the transition movie. The distance field is intended for use with 3D applications, but is also not used by QuickTime VR.

Link Hot Spot Valid Flags

The toValidFlags field in the link hot spot atom structure specifies which view settings are to be used when moving to a destination node from a hot spot. You can use these bit flags to specify a value for that field:

enum {

    kQTVRValidPan                               = 1 << 0,

    kQTVRValidTilt                              = 1 << 1,

    kQTVRValidFOV                               = 1 << 2,

    kQTVRValidViewCenter                        = 1 << 3

};

Constant descriptions

kQTVRValidPan

The setting for using the destination pan angle.

kQTVRValidTilt

The setting for using the destination tilt angle.

kQTVRValidFOV

The setting for using the destination field of view.

kQTVRValidViewCenter

The setting for using the destination view center.

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