Intrinsic matrix estimation for non planar objects (Feature #623)

I transformed a small piece of code I found at the MATLAB calibration toolbox, regarding the initialization of intrinsic matrix for non planar objects. It might be useful for other people. I tested it with my data and the the reconstruction seems to be working.

 1CvMat *initIntrinsicMatrix(int width, int height, float fovAngle=35)
 2{
 3    CvMat *intrinsicMatrix = cvCreateMat(3, 3, CV_32FC1);
 4    cvSetIdentity(intrinsicMatrix);
 5
 6    float fc = ((float)width/2) / (float)tan(PI * fovAngle / 360.0f);
 7
 8        cvmSet(intrinsicMatrix, 0, 0, fc);
 9    cvmSet(intrinsicMatrix, 1, 1, fc);            
10    cvmSet(intrinsicMatrix, 0, 2, (float)width / 2);
11    cvmSet(intrinsicMatrix, 1, 2, (float)height / 2);                    
12
13    return intrinsicMatrix;
14}