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    <p>I raised this question because I wasn't able to figure out a solution (it is not only today that I was dealing with the matter hehe), but after all I was able to manage the problem! </p> <p>I had to change the way I calculated the convex hull, using the index array form. So now we have a vector&lt; int > instead a vector&lt; Point >.</p> <p>This is the code I used (it works I painted the points over an image):</p> <pre><code>void HandDetection::findConvexityDefects(vector&lt;Point&gt;&amp; contour, vector&lt;int&gt;&amp; hull, vector&lt;Point&gt;&amp; convexDefects){ if(hull.size() &gt; 0 &amp;&amp; contour.size() &gt; 0){ CvSeq* contourPoints; CvSeq* defects; CvMemStorage* storage; CvMemStorage* strDefects; CvMemStorage* contourStr; CvConvexityDefect *defectArray = 0; strDefects = cvCreateMemStorage(); defects = cvCreateSeq( CV_SEQ_KIND_GENERIC|CV_32SC2, sizeof(CvSeq),sizeof(CvPoint), strDefects ); //We transform our vector&lt;Point&gt; into a CvSeq* object of CvPoint. contourStr = cvCreateMemStorage(); contourPoints = cvCreateSeq(CV_SEQ_KIND_GENERIC|CV_32SC2, sizeof(CvSeq), sizeof(CvPoint), contourStr); for(int i=0; i&lt;(int)contour.size(); i++) { CvPoint cp = {contour[i].x, contour[i].y}; cvSeqPush(contourPoints, &amp;cp); } //Now, we do the same thing with the hull index int count = (int)hull.size(); //int hullK[count]; int* hullK = (int*)malloc(count*sizeof(int)); for(int i=0; i&lt;count; i++){hullK[i] = hull.at(i);} CvMat hullMat = cvMat(1, count, CV_32SC1, hullK); //We calculate convexity defects storage = cvCreateMemStorage(0); defects = cvConvexityDefects(contourPoints, &amp;hullMat, storage); defectArray = (CvConvexityDefect*)malloc(sizeof(CvConvexityDefect)*defects-&gt;total); cvCvtSeqToArray(defects, defectArray, CV_WHOLE_SEQ); //printf("DefectArray %i %i\n",defectArray-&gt;end-&gt;x, defectArray-&gt;end-&gt;y); //We store defects points in the convexDefects parameter. for(int i = 0; i&lt;defects-&gt;total; i++){ CvPoint ptf; ptf.x = defectArray[i].depth_point-&gt;x; ptf.y = defectArray[i].depth_point-&gt;y; convexDefects.push_back(ptf); } //We release memory cvReleaseMemStorage(contourStr); cvReleaseMemStorage(strDefects); cvReleaseMemStorage(storage); } } </code></pre> <p>This worked for me. If you see something wrong or another way to manage it, please tell me!</p>
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    1. COHey just wondering, but why did you use a CvMat instead of a sequence for the hull argument in cvConvexityDefects ()? Thank You.
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    2. COHi, it is because I needed for the cvConvexityDefects some kind of sequence of any type (const void* convexhull) and CvMat came to my mind, but in fact, the examples I found on the web use a CvSeq*, so I think you can use it.
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    3. COThank You. Just one more question. Instead of making hullK a pointer, would this still work by just using a normal array? For example, instead of what you did, would using "int hullK [hull.size ()]" work? I'm just wondering as I don't have access to a compiler right now so I can't test it out.
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