I have previously asked the question "Use calibrated camera get matched points for 3D reconstruction", but the problem was not described clearly. So here I use a detail case with every step to show. Hope there is someone can help figure out where my mistake is.
At first I made 10 3D points with coordinates:
>> X = [0,0,0;
-10,0,0;
-15,0,0;
-13,3,0;
0,6,0;
-2,10,0;
-13,10,0;
0,13,0;
-4,13,0;
-8,17,0]
these points are on the same plane showing in this picture: http://oi59.tinypic.com/jjvh8w.jpg
My next step is to use the 3D-2D projection code to get the 2D coordinates. In this step, I used the MATLAB code from caltech calibration toolbox called "project_points.m". Also I used the OpenCV C++ code to verify the result and turned out the same. (I used cvProjectPoints2())
For the 1st projection, parameters are:
>> R = [0, 0.261799387, 0.261799387]
>> T = [0, 20, 100]
>> K = [12800, 0, 1850; 0, 12770, 1700; 0 0 1]
And no distortion
>> DisCoe = [0,0,0,0]
The rotation is just two rotations with pi/12. I then got the 1st view 2D coordinates:
>> Points1 = [1850, 4254;
686.5, 3871.7;
126.3, 3687.6;
255.2, 4116.5;
1653.9, 4987.6;
1288.6, 5391.0;
37.7, 4944.1;
1426.1, 5839.6;
960.0, 5669.1;
377.3, 5977.8]
For the 2nd view, I changed:
>> R = [0, -0.261799387, -0.261799387]
>> T = [0, -20, 100]
And then got the 2nd View 2D coordinates:
>> Points2 = [1850, -854;
625.4, -585.8;
-11.3, -446.3;
348.6, -117.7;
2046.1, -110.1;
1939.0, 442.9;
588.6, 776.9;
2273.9, 754.0;
1798.1, 875.7;
1446.2, 1501.8]
THEN will be the reconstruction steps, I have already built the ideal matched points(I guess so), next step is to calculate the Fundamental Matrix, using estimateFundamentalMatrix():
>> F = [-0.000000124206906, 0.000000155821234, -0.001183448392236;
-0.000000145592802, -0.000000088749112, 0.000918286352329;
0.000872420357685, -0.000233667041696, 0.999998470240927]
with known K, I used the matlab code below to calculate essential matrix and compute the R, t, finally 3D coordinates:
E = K'*F*K;
[u1,w1,v1] = svd(E);
t = (w1(1,1)+w1(2,2))/2;
w1_new = [t,0,0;0,t,0;0,0,0];
E_new = u1*w1_new*v1';
[u2,w2,v2] = svd(E_new);
W = [0,-1,0;1,0,0;0,0,1];
S = [0,0,-1];
P1 = K*eye(3,4);
R = u2*W'*v2';
t = u2*S;
P2 = K*[R t];
for i=1:size(Points1,1)
A = [P1(3,:)*Poinst1(i,1)-P1(1,:);P1(3,:)*Points1(i,2)-P1(2,:);P2(3,:)*Points2(i,1)-P2(1,:);P2(3,:)*Points2(i,2)-P2(2,:)];
[u3,w3,v3] = svd(A);
dpt(i,:) = [v3(1,4) v3(2,4) v3(3,4)];
end
From this code I got the result as below:
>>X_result = [-0.00624167168027166 -0.0964921215725801 -0.475261364542900;
0.0348079221692933 -0.0811757557821619 -0.478479857606225;
0.0555763217997650 -0.0735028994611970 -0.480026199527202;
0.0508767193762549 -0.0886557226954657 -0.473911682320574;
0.00192300693541664 -0.121188713743347 -0.466462048338988;
0.0150597271598557 -0.133665834494933 -0.460372995991565;
0.0590515135110533 -0.115505488681438 -0.460357357303399;
0.0110271144368152 -0.148447743355975 -0.455752218710129;
0.0266380667320528 -0.141395768700202 -0.454774266762764;
0.0470113238869852 -0.148215424398514 -0.445341461836899]
With showing these points in Geomagic, the result is "a little bit bending". But there positions seemed right. I don't know why this happened. Anybody have some idea? Please see the picture: http://oi59.tinypic.com/n6t63t.jpg
