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

//== NaturalPoint Motive API Calibration Sample Application ==

#include <windows.h>
#include <conio.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string>

#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);
    }
}

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.

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

TTAPI bool  TT_SetGroundPlane( float verticalOffset );