Hi,
I am trying to create a visual odometry app for android using NDK. I am using FAST and KLT and then using findEssentialMat to find the essential matrix. However, it is giving erroneous results. Here's some debug output:
04-17 23:23:28.313 2630-2903/com.example.shaswat.testopencv D/OCVSample::SDK: Essential Matrix =
04-17 23:23:28.313 2630-2903/com.example.shaswat.testopencv D/OCVSample::SDK: -0.000000
04-17 23:23:28.313 2630-2903/com.example.shaswat.testopencv D/OCVSample::SDK: -1.655305
04-17 23:23:28.313 2630-2903/com.example.shaswat.testopencv D/OCVSample::SDK: 29303136256.000000
04-17 23:23:28.313 2630-2903/com.example.shaswat.testopencv D/OCVSample::SDK: -182220068263779929277612730010501644288.000000
04-17 23:23:28.313 2630-2903/com.example.shaswat.testopencv D/OCVSample::SDK: 1.771581
04-17 23:23:28.314 2630-2903/com.example.shaswat.testopencv D/OCVSample::SDK: 0.000000
04-17 23:23:28.314 2630-2903/com.example.shaswat.testopencv D/OCVSample::SDK: -598.520691
04-17 23:23:28.314 2630-2903/com.example.shaswat.testopencv D/OCVSample::SDK: 1.350371
04-17 23:23:28.314 2630-2903/com.example.shaswat.testopencv D/OCVSample::SDK: 152428905045575845543936.000000
The essential matrix values are displayed column-wise. My code is as follows:
Java part - onCameraFrame()
public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {
this.mCurr = inputFrame.rgba();
if(this.firstRun == 1){
this.mCurr = inputFrame.rgba();
this.mPrev = inputFrame.rgba();
this.mDisplay = inputFrame.rgba();
this.firstRun = 0;
this.mRf = new Mat(3, 3, CvType.CV_32F);
this.mRf.put(0,0,0,0,0,0,0,0,0,0,0);
this.mTf = new Mat(3, 1, CvType.CV_32F);
this.mTf.put(0,0,0,0,0);
}
this.controlFrameRate++;
if(this.controlFrameRate<2)
return null;
this.controlFrameRate = 0;
if(this.firstRun == 0) {
this.mDisplay = this.mPrev;
convertNativeGray(mCurr.getNativeObjAddr(), mPrev.getNativeObjAddr(), mDisplay.getNativeObjAddr(), mRf.getNativeObjAddr(), mTf.getNativeObjAddr());
this.mPrev = this.mCurr;
}
return mDisplay;
}
Native part:
JNIEXPORT jint JNICALL Java_com_example_shaswat_testopencv_MainActivity_convertNativeGray(JNIEnv*, jobject, jlong addrCurr, jlong addrPrev, jlong addrDisplay, jlong addrRF, jlong addrTF) {
__android_log_print(ANDROID_LOG_DEBUG, "OCVSample::SDK","In Native Code");
Mat& mCurr = *(Mat*)addrCurr;
Mat& mPrev = *(Mat*)addrPrev;
Mat& mDisplay = *(Mat*)addrDisplay;
Mat& R_f = *(Mat*)addrRF;
Mat& t_f = *(Mat*)addrTF;
int conv = 0;
jint retVal;
cvtColor(mCurr, mCurr, CV_RGBA2BGR);
cvtColor(mPrev, mPrev, CV_RGBA2BGR);
cvtColor(mDisplay, mDisplay, CV_RGBA2BGR);
//mDisplay = cv::Mat::zeros(mCurr.rows, mCurr.cols, mCurr.type());
Mat cameraMatrix = (Mat_(3,3) << 1097.1547, 0.0, 403.9075, 0.0, 821.5675, 298.8437, 0.0, 0.0, 1.0);
VO::featureOperations odometry(cameraMatrix, mCurr, mPrev, mDisplay, R_f, t_f, 1);
odometry.calcOdometry(cameraMatrix, mCurr, mPrev, mDisplay, R_f, t_f, 1);
cvtColor(mCurr, mCurr, CV_BGR2RGBA);
cvtColor(mPrev, mPrev, CV_BGR2RGBA);
cvtColor(mDisplay, mDisplay, CV_BGR2RGBA);
retVal = (jint)conv;
return retVal;
}
calcOdometry function:
void VO::featureOperations::calcOdometry(cv::Mat cameraMatrix, cv::Mat currImage, cv::Mat prevImage, cv::Mat& trajectory, cv::Mat& R_f, cv::Mat& t_f, int enableHomography){
// Change these accordingly. Intrinsics
double focal = cameraMatrix.at(0,0);
cv::Point2d pp(cameraMatrix.at(0,2), cameraMatrix.at(1,2));
// recovering the pose and the essential matrix
cv::Mat E, R, t, mask;
std::vector status;
std::vector prevFeatures;
std::vector currFeatures;
prevFeatures = this->detectFeatures(prevImage);
// For FAST
if(this->trackFeatures(prevImage,currImage,prevFeatures,currFeatures,status)){
if(prevFeatures.size()>200 && currFeatures.size()>200)
{
E = cv::findEssentialMat(currFeatures, prevFeatures, focal, pp, cv::RANSAC, 0.999, 1.0, mask);
cv::recoverPose(E, currFeatures, prevFeatures, R, t, focal, pp, mask);
}
else
{
R = cv::Mat::zeros(3, 3, CV_32F);
t = cv::Mat::zeros(3, 1, CV_32F);
}
}
// a redetection is triggered in case the number of feautres being trakced go below a particular threshold
if (prevFeatures.size() < 1800) {
prevFeatures=this->detectFeatures(prevImage);
this->trackFeatures(prevImage,currImage,prevFeatures,currFeatures, status);
}
}
std::vector VO::featureOperations::detectFeatures(cv::Mat img){
cv::cvtColor(img,img,cv::COLOR_BGR2GRAY);
// Detect features on this image
std::vector pointsFAST;
std::vector keypoints_FAST;
// FAST Detector
int fast_threshold = 20;
bool nonmaxSuppression = true;
cv::FAST(img,keypoints_FAST,fast_threshold,nonmaxSuppression);
cv::KeyPoint::convert(keypoints_FAST,pointsFAST,std::vector());
assert(pointsFAST.size() > 0);
return pointsFAST;
}
bool VO::featureOperations::trackFeatures(cv::Mat prevImg, cv::Mat currentImg, std::vector& points1, std::vector& points2, std::vector& status){
cv::Mat prevImg_gray,currentImg_gray;
cv::cvtColor(prevImg,prevImg_gray,CV_BGR2GRAY);
cv::cvtColor(currentImg,currentImg_gray,CV_BGR2GRAY);
std::vector err;
cv::Size winSize=cv::Size(21,21);
cv::TermCriteria termcrit=cv::TermCriteria(cv::TermCriteria::COUNT+cv::TermCriteria::EPS, 30, 0.01);
cv::calcOpticalFlowPyrLK(prevImg_gray, currentImg_gray, points1, points2, status, err, winSize, 3, termcrit, 0, 0.001);
//getting rid of points for which the KLT tracking failed or those who have gone outside the frame
int indexCorrection = 0;
for( int i=0; i
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