Motive API Camera Calibration

Main Page → Developer Tools → Motive API → Quick Start Guide → Motive API Camera Calibration

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Page Scope

This page provides a sample and instructions on how to use Motive API functions to calibrate a camera system.

Sample Code

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The following sample code demonstrates calibration process using the Motive API. For details on specific functions, please refer to the Motive API: Function Reference page.

Wanding

<source> //== NaturalPoint Motive API Calibration Sample Application ==

1. include <windows.h>
2. include <conio.h>
3. include <stdio.h>
4. include <stdlib.h>
5. include <math.h>
6. include <string>

1. include "NPTrackingTools.h"

// Local function prototypes void CheckResult( NPRESULT result );

std::string CalibrationStateString( TT_CameraCalibrationStates state ) {

   switch( state )
   {
       case TT_CameraCalibration_Initialized:   return "Init    ";
       case TT_CameraCalibration_Sampling:      return "Sampling";
       case TT_CameraCalibration_Solving:       return "Solving ";
       case TT_CameraCalibration_Complete:      return "Complete";
       case TT_CameraCalibration_Uninitialized: break;
       default: break;
   }

   return "Unknown ";

}

// Main application int main( int argc, char* argv[] ) {

   printf( "== NaturalPoint Motive API Calibration Sample Application =======---\n" );
   printf( "== (C) NaturalPoint, Inc.\n\n" );

   printf( "Initializing NaturalPoint Devices\n" );
   
   if( TT_Initialize() != NPRESULT_SUCCESS )
   {
       printf( "Unable to license Motive API\n" );
       return 1;
   }

   // Do an update to pick up any recently-arrived cameras.
   TT_Update();

   // List all detected cameras.
   printf( "Cameras:\n" );
   for( int i = 0; i < TT_CameraCount(); i++)
   {
       printf( "\t%s\n", TT_CameraName(i) );
   }
   printf("\n");

   //== lets set our wand settings ==--

   cCameraCalibrationSettings settings;
   settings.WandLength       = 0.250;  // wand length        = 250mm
   settings.WandCenterOffset = 0.0875; // wand center offset = 87.5mm

   if( TT_SetCalibrationSettings( settings ) != NPRESULT_SUCCESS )
   {
       printf( "Unable to set camera calibration settings.\n\n" );
   }

   if( TT_CalibrationSettings( settings ) == NPRESULT_SUCCESS )
   {
       //== fetch & print default wand settings ==--

       printf( "Wand Length        = %.1fmm\n", settings.WandLength * 1000 );
       printf( "Wand Center Offset = %.1fmm\n", settings.WandCenterOffset * 1000 );
   }
   else
   {
       printf( "Unable to fetch camera calibration settings.\n\n" );
   }

   printf( "\n" );
   printf( "Press 1: Start Wanding\n" );
   printf( "Press 2: Start Calculation\n" );
   printf( "Press 3: Apply Calibration\n" );
   printf( "Press 4: Reset\n" );
   printf( "\n" );

   int frameCounter = 0;
   
   bool done = false;
   while( !done )
   {
       if( _kbhit() )
       {
           char c = _getch();

           if( c == '1' )
           {
               printf( "Start Wanding: " );
               if( TT_StartCalibrationWanding() )
               {
                   printf( "Success\n" );
               }
               else
               {
                   printf( "Failed\n" );
               }
           }
           if( c == '2' )
           {
               printf( "Start Solving: " );
               if( TT_CameraCalibrationSolve() )
               {
                   printf( "Success\n" );
               }
               else
               {
                   printf( "Failed\n" );
               }
           }
           if( c == '3' )
           {
               printf( "Apply Calibration: " );
               if( TT_CameraCalibrationApplyResult() )
               {
                   printf( "Success\n" );
               }
               else
               {
                   printf( "Failed\n" );
               }

           }
           if( c == '4' )
           {
               printf( "Reset Calibration: " );
               if( TT_CameraCalibrationReset() )
               {
                   printf( "Success\n" );
               }
               else
               {
                   printf( "Failed\n" );
               }
           }
       }
       if( TT_Update() == NPRESULT_SUCCESS )
       {
           frameCounter++;

           if( (frameCounter%100) == 0 )
           {

//== every 100 frames print ongoing sample and calibration state information ==--

               printf( "Frame[%5d] Markers[%3d] Calibration State[%s] ", frameCounter, TT_FrameMarkerCount(), CalibrationStateString( TT_CalibrationState()).c_str() );

               if( TT_CalibrationState() == TT_CameraCalibration_Sampling )
               {
                   for( int index = 0; index < TT_CameraCount(); index++ )
                   {
                       printf( "%d ", TT_CameraCalibrationSamples( index ) );
                   }

                   printf( "\n\nWand Location\n" );
                   printf( "-----------------------\n" );

                   float points[ 6 ];

                   for( int index = 0; index < TT_CameraCount(); index++ )
                   {

                       bool wandPresent = TT_CameraWandLocation( index, points );

                       printf( "Camera #%d: ", index );
                       if( wandPresent )
                       {
                           printf( "[Present    ] " );

                           for( int pointIndex = 0; pointIndex < 6; pointIndex += 2 )
                           {
                               printf( "%.1f,%.1f ", points[ pointIndex ], points[ pointIndex + 1 ] );
                           }
                       }
                       else
                       {
                           printf( "[Not Present] " );
                       }
                       printf( "\n" );
                   }
                   printf( "\n" );
               }

               printf( "\n" );
           }
       }
       Sleep(2);
   }

   printf( "Shutting down NaturalPoint Motive API\n" );
   CheckResult( TT_Shutdown() );

   printf( "Complete\n" );
   while( !_kbhit() )
   {
       Sleep(20);
   }

   return 0;

}

void CheckResult( NPRESULT result ) //== CheckResult function will display errors and ---

                                     //== exit application after a key is pressed =====---

{

   if( result!= NPRESULT_SUCCESS)
   {
       // Treat all errors as failure conditions.
       printf( "Error: %s\n\n(Press any key to continue)\n", TT_GetResultString(result) );

       Sleep(20);
       exit(1);
   }

} </source>

Ground Plane

Setting ground plane is done directly by calling the TT_SetGroundPlane function. When this is called, camera system will search for 3-markers that resemble a calibration square and uses the inputted vertical offset value to configure the ground plane.

<source> //== To apply ground plane, call TT_SetGroundPlane(). Specify the vertical offset from the marker centers in meters.

TTAPI bool TT_SetGroundPlane( float verticalOffset ); </source>