OpenCV Q&A Forum - RSS feedhttp://answers.opencv.org/questions/OpenCV answersenCopyright <a href="http://www.opencv.org">OpenCV foundation</a>, 2012-2018.Mon, 09 Jul 2018 03:38:44 -0500Is there a approximation error in the fisheye camera modelhttp://answers.opencv.org/question/195305/is-there-a-approximation-error-in-the-fisheye-camera-model/ At [https://docs.opencv.org/master/db/d58/group__calib3d__fisheye.html](https://docs.opencv.org/master/db/d58/group__calib3d__fisheye.html), it says
![image description](/upfiles/15311245222762372.png)
![image description](/upfiles/15311249905829676.png)
If the fisheye distortion is and only is changing theta to theta_d, and after the distortion, use pinhole projection,
then a more reasonable formula is
![image description](/upfiles/1531125286488948.png)
That is, tan(theta_d) should be used instead of theta_d to calculate x' and y'.
Is this a approximation error here?HaiqiangZhangMon, 09 Jul 2018 03:38:44 -0500http://answers.opencv.org/question/195305/Capability of OpenCVhttp://answers.opencv.org/question/62474/capability-of-opencv/Say you have a camera pointing at an object in real life. The computer knows the location and orientation of the camera relative to the object
Then say you have a 3D model of that object in memory.
Is it possible with OpenCV to project the camera image onto the 3D model of the object, returning a texture/image for each face of the object?
If OpenCV can't do this, does anyone know any other program or package that can do this, in a way I can call with code or a script and an input file?ajs138Sat, 23 May 2015 04:52:38 -0500http://answers.opencv.org/question/62474/fisheye::calibratehttp://answers.opencv.org/question/55467/fisheyecalibrate/ Hi,
Does everyone knows which paper has been implemented for this fish eye camera model?
Thank youmartoonTue, 17 Feb 2015 02:52:16 -0600http://answers.opencv.org/question/55467/The coordinate system of pinhole camera modelhttp://answers.opencv.org/question/31470/the-coordinate-system-of-pinhole-camera-model/Recently, I have been studying the pinhole camera model for several days but I was confused with the model provided by OpenCV and "Multiple View geometry in computer vision" which is a famous textbook.
I know that the following photo is a simplified model which switches the position of the image plane and the camera frame. Basically,for better illustration and understanding and Taking consideration of the principal point (u0,v0), the relation between two frames is
x=f(X/Z)+u0 and
y=f(Y/Z)+vo.
![image description](/upfiles/1397050375379081.png)
However,I was really confused because normally the image coordinate is in the form of the 4th quadrant coordinate as the following one!
Could I directly substitute the (x,y) in the following definition to the above "equivalent" pinhole model which is not really persuasive?
![image description](/upfiles/13970504447802913.gif)
Besides, If an object is in the region (+X,+Y) quadrant in the camera coordinate (of course, Z>f), in the equivalent model, it should appear on the right-half plane of the image coordinate. However, such object in the image taken by a normal camera, it is supposed to be located on the left-half. Therefore, for me this model is not reasonable.
Finally, I tried to derive based on the original model as the following one.
![image description](/upfiles/13970504813232063.png)
The result is
x1=-f(X/Z) and
y1=-f(Y/Z). Then, I tried to find the relation between (x2,y2)-coordinate and the camera coordinate. The result is
x2=-f(X/Z)+u0 and
y2=-f(Y/Z)+vo.
Between (x3,y3)-coordinate and the camera coordinate, the result is
x3=-f(X/Z)+u0 and
y3=f(Y/Z)+vo.
no matter which coordinate system i tried, none of them is in the form of
x=f(X/Z)+u0 and
y=f(Y/Z)+vo, which are provided by some CV textbooks.
Besides, the projection results on (x2,y2)-coordinate or (x3,y3)-coordinate are also not reasonable because of the same reason- an object in the (+X,+Y,+Z) region in the camera coordinate should "appear" on the left-half plane of the image taken by a camera.
Could anyone indicate what I was misunderstood with and I will try to derive several times more and post the answer when someone else help me figure this issue out.
Thank you in advance!!
AlexAlexofNTUWed, 09 Apr 2014 08:37:31 -0500http://answers.opencv.org/question/31470/