5.5 - The Observer API

Table of Contents

• 5.5.1 Controlling the Observer

Application code can access an observer by:

• Connecting to the signal_observerCreated from the DtInputDriverSignaler
• Using one of the DtInputDriver's accessors to retrieve the current observer, or any observer by its name.

Both of these mechanisms result in a pointer to a DtObserver.

The DtObserver class is a facade for the DtObserverObjectAgent, which is itself the interface for the distributed DtObserverObjects it controls. Calls to DtObserverObjectAgent methods are distributed to all of the agent's DtObserverObjects. The DtObserver class is intended to simplify some operations on observers. However, it is always possible to access the agent itself from the DtObserver and make calls directly. There are many methods that you can call to control an observer.

5.5.1 Controlling the Observer

DtObserverObjects are controlled in the local (database) coordinate system. Given a pointer to an observer, pObserver, a call to set a DtObserverObject's location would look like:

pObserver->setLocation( desiredX, desiredY, desiredZ );

You can specify orientation using Tait-Bryan angles or quaternions:

pObserver->setOrientation( desiredPsi, desiredTheta, desiredPhi );
pObserver->setOrientation( xQuat, yQuat, zQuat, wQuat );

You can specify the observer location with the following:

pObserver->setLocation( databaseLocationX, databaseLocationY, databaseLocationZ );

The observer uses the database coordinates. VR-Vantage customers who need to work in geocentric coordinates should use a geocentric database. If you need to convert a geocentric location to a non-geocentric database location use:

myDe.sharedState().coordinateSystem().netToLocalPos( geocentricLocation, databaseLocation );

Methods also exist for setting attachments, attach modes, and all the parameters typically associated with those modes.

The keyboard-based navigation code does not set the location and orientation of the observer directly. It uses commands to start and stop observer movement. These methods are not part of the DtObserver facade. You can call them directly on the DtObserverObjectAgent. For example:

pObserver->agent()->startMoveObserverForward();
pObserver->agent()->stopMoveObserverForward();

You can retrieve information about the observer's location, orientation, current attachments and modes, and so on. Please see DtObserver and DtObserverObject for all the methods available

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