cisst Trackers need easy way to get multiple frames at same timestamp

[pkazanzides]

There is a serious need to get multiple rigid body frames that correspond to the same timestamp.

[marcinbalicki]

Since the tracker frames are all in the same state table and updated at the same time, it is possible to use table index accessed through any interface to access the frame with the same timestamp from another interface. A single method to get all frames would be nice.

I have added the state table index accessor to the state table.
jhu-saw/sawNDITracker@dc19615

Here is an example in python that retrieves 3 tracking body frames corresponding to a single acquisition
:

# INIT
    #create an interface for the tracked pointer body
        trackedBodyName = 'Tool'
        self.ToolBody = proxyComponent.AddInterfaceRequiredAndConnect((name, trackedBodyName))

        #create an interface for the tracked pointer body
        trackedBodyName = 'Arm'
        self.ArmBody = proxyComponent.AddInterfaceRequiredAndConnect((name, trackedBodyName))

        #create an interface for the tracked pointer body
        trackedBodyName = 'Base'
        self.BaseBody = proxyComponent.AddInterfaceRequiredAndConnect((name, trackedBodyName))

        self.GetArmPoseQR = self.ArmBody.GetFunctionQualifiedRead('GetPositionCartesian')
        self.GetArmPoseQR.UpdateFromC();

        self.GetToolPoseQR = self.ToolBody.GetFunctionQualifiedRead('GetPositionCartesian')
        self.GetToolPoseQR.UpdateFromC();

        self.GetBasePoseQR = self.BaseBody.GetFunctionQualifiedRead('GetPositionCartesian')
        self.GetBasePoseQR.UpdateFromC();

 def GetAllPoses(self):
        stateIndex = self.ToolBody.GetTableIndex()
        trTool = self.ConvertPosCartToFrame(self.GetToolPoseQR(stateIndex))
        trArm = self.ConvertPosCartToFrame(self.GetArmPoseQR(stateIndex))
        trBase = self.ConvertPosCartToFrame(self.GetBasePoseQR(stateIndex))
        return trTool, trArm, trBase