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2016-02-04 19:24:43 -0500 commented question opencv RANSAC random sequence

thank you for your comment berak. is there any way to give another seed to RANSAC?

2016-02-04 03:24:28 -0500 asked a question opencv RANSAC random sequence

i use findhomography and findfundamental algorithm in my code.

but when i use this with ransac

findHomography(src_points, dst_points, Matches_Info.inliers_mask, CV_RANSAC, 3.0);
findFundamentalMat(src_points, dst_points, Matches_Info.inliers_mask, CV_RANSAC, 3.0, 0.99);

like this

it always gets me same result.

but RANSAC algorithm use random sample to build model. so it have to has some different between other running.

i think this problem cause from random sequence of Opencv's RANSAC algorithm

but i can't find any information about this.

am i right? or if you have any information about this please comment me.

thank you.

2016-02-01 07:54:44 -0500 received badge  Student (source)
2016-02-01 07:36:00 -0500 asked a question descriptor matching performance between ORB and SIFT

Hi i'm student in master's degree in geoinformatic.

i have question about descriptor matching from opencv feature extraction.

i learned that SIFT descriptor matching is slower than ORB cause of it's data type and matching factor(euclidean and hamming distance)

but in my algorithm in SIFT case is faster than ORB case.

i use FlannBasedMatcher for matching

this is my code :

Ptr<flann::IndexParams>  indexParams = new flann::KDTreeIndexParams();
Ptr<flann::SearchParams> searchParams = new flann::SearchParams();

if (Features2.descriptors.depth() == CV_8U)
{
    indexParams->setAlgorithm(cvflann::FLANN_INDEX_LSH);
    searchParams->setAlgorithm(cvflann::FLANN_INDEX_LSH);
}   

FlannBasedMatcher matcher(indexParams, searchParams);
vector<vector<DMatch> > pair_matches;
matcher.knnMatch(Features1.descriptors, Features2.descriptors, pair_matches, 2);

i think if i use ORB(8U) for descriptor than it will use FLANN_INDEX_LSH for matching.

but in this case it takes more time than SIFT(32F).

i saw that someone said LSH is not getting hamming distance really. but it's similar with hamming distance.

and someone said in FlannBasedMatcher use 32F data type for calculating.

but i can't find what's right and why it takes more time. so im thoroughly confused.

please tell me what's wrong in my code. or reason of slow matching in ORB descriptor.

thank you.