I have a very peculiar request. I have a view matrix (one used for gD3dDevice->SetTransform( D3DTS_VIEW, &viewMatrix );) and I need to reverse it to find the yaw, pitch and roll. How can I do that? I have been following the instructions on http://www.toymaker.info/Games/html/camera.html
This is a quite complicated, inexact and ambiguous task. If you can work around your problem by not calculating euler-angles, do it :)
However, here is some reading and also some code for you:
http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToEuler/index.htm
Related
I built a stereoscopic camera mobile app which performs automatic alignment using findTransformEcc and the app is working pretty well with it. I know I should probably be using rectifyStereoUncalibrated preceded by keypoints and descriptors etc. etc. but I get bad results from that despite many different approaches attempted and I'm super frustrated. So instead, I'm sticking with findTransformEcc (at least for now). At the moment I'm using MotionType.Euclidean (restricted to translations and rotations) but I would like to change that.
So far, the app has worked by having the user take one picture and move to the side to capture the next (chacha method). But now I'm adding the ability to have two phones capture simultaneously. The problem is that the focal length and sensor size (angular field of view) may be different between the two cameras, so in order to align the two pictures I need to allow scaling/zooming. However, if I want to do that with findTransformEcc I can only step up from Euclidean to Affine, it seems like I can't go between. That is, it seems I cannot allow scaling without also allowing shearing, and I don't want shearing.
As another way to explain this, I'd like to get the type of transform that you can get from estimateRigidTranform(array,array,FALSE) (partial affine) but rather than using keypoints as that function does, I want to use findTransformEcc because from my experimentation it just seems to be more reliable.
(https://github.com/KRA2008/crosscam/blob/develop/AutoAlignment/OpenCV.cs is the auto-alignment code if that helps at all)
Take a look at Fourier-Mellin transform based approach: https://github.com/Smorodov/LogPolarFFTTemplateMatcher
It will give you offset, scale and rotation parameters, nothing more.
I tried the code written here:
http://i-vizon.blogspot.ch/2013/03/optical-flow-using-opencv-library-on.html
It works pretty well, but does not perform well in the case of moving camera, because all features are removed on scene change.
Fundamentally the code is so composed:
First frame: goodFeaturesToTrack(grayFrames,points1,MAX_COUNT,0.01,5,Mat(),3,0,0.04);
Other frames:
calcOpticalFlowPyrLK(prevGrayFrame,grayFrames,points2,points1,status,err,winSize,3,termcrit,0,0.001);
goodFeaturesToTrack(grayFrames,points1,MAX_COUNT,0.01,10,Mat(),3,0,0.04);
with the swapping of points and copy of the current frame in the previous.
Problem:
when I use it with camera, handling it on my hand, when I change the first scenes no optical flow is produced, I suppose because initial features are not more contained in the new frames.
How I can refresh the feature point in this code to continue working?
Which is a good refresh condition? Based for example on the the number of features?
Thank you very much.
Ok, I've done some reading around the subject, have an idea of how I'd tackle my problem, but want to find out of this is the most efficient way, or if I'm missing something simple.
I have a line diagram of a section of railway that I'd like to plot the users location onto (the user being someone on a train moving up/down the railway).
Now, I initially went down the route of geo-referencing, but quickly realised this probably wasn't the way to go, as my image is not a real reflection of the area + I want the line diagram to be what the user sees.
OK, my though process of how I will tackle it:
I know the physical area so I could extract the coordinates along the railway, every x meters (my line diagram has a resolution of around 5m). Stick this into an array. Can anyone suggest a tool to do this?!
Allocate my line diagram a start and end, then match the image coordinates with the physical coordinates for the entire line.
Read in the users position and update where to draw the position based on the closest match in the array?
Does this sound doable, and would it give me decent results?
If you have more sophisticated answers, please do share.
It sounds reasonable in general. As the user is supposed to be on a train a simpler option may work where you just keep track of the physical distance moved and use that as a percentage distance along the line. This is a lot simpler to manage and could be backed up with some coordinate checkpoints to ensure you don't have a drifting error. I'd aim for a simpler implementation if you can.
I'm coding iOS app that will explain complex numbers to the user. Complex numbers can be displayed in Cartesian coordinates and that's what I want to do; print one or more vectors on the screen.
I am looking for the easiest way to print 3 vectors into a coordinate system that will adjust itself to the vector-size (if x-coord is > y-coord adjust both axis to x-coord and vice versa).
I tried using Core Plot, which I think is way too multifunctional for my purpose.
Right now I am working with PowerPlot and my coordinate system looks okay already, but I still encounter some problems (x- and y-axis are set to the x and y values which results in a 45 degree angled line, no matter the user input).
The functionality of the examples in CorePlot and PowerPlot don't seem to meet my needs.
My last two approaches were using HTML and a web view, and doing it all myself with Quartz (not the simple way...)
Do you have any advice how to do this the simple way, as it is a simple problem, I guess?
If you're not wanting to do much actual graphing and plotting, then using Core Plot or similar sounds like overkill to me. The extra bloat of adding coreplot to your project, not to mention the time taken for you to understand how to use it, might not be worth it for some simple graphics.
Quartz is well equipped for the job of showing a few vectors on the screen, assuming you're not interested in fancy 3D graphics. There are plenty of tutorials and examples of using Core Graphics (AKA Quartz) to draw lines etc. If you're going the Quartz route, perhaps get some simple line drawing going in Quartz, then ask more questions if you need help with the maths aspect of it.
The typical technique used when rendering with Quartz is to override drawRect in a subclass of UIView and place calls to Core Graphics drawing functions in there.
A decent question and example of Quartz line drawing is here:
How do I draw a line on the iPhone?
If you aren't adverse to using Google Chart Image you can load reasonably complex data sets in a simple manner by calling the appropriate URL and then putting the image in a UIImageView. It takes very little code: here is a blog post explanation with sample code.
The limitations are
length of the data set is restricted by the max URL length you can request from Google (2048 characters, with encoding is large), though I've plotted with 120 data points in 4 series.
a net connection is required (at least to get the initial chart)
and perhaps the biggest problem, API is deprecated and will be discontinued in 2015 at some point. You would then have to switch to the UIWebView/Javascript Google Chart API implementation...
Sample image:
iam working in a project that i take a vedio by a camera and convert this vedio to frames (this part of project is done )
what iam facing now is how to detect moving object in these frames and differentiate them from the background so that i can distinguish between them ?
I recently read an awesome CodeProject article about this. It discusses several approaches to the problem and then walks you step by step through one of the solutions, with complete code. It's written at a very accessible level and should be enough to get you started.
One simple way to do this (if little noise is present, I recommend smoothing kernel thought) is to compute the absolute difference of two consecutive frames. You'll get an image of things that have "moved". The background needs to be pretty static in order to work. If you always get the abs diff from the current frame to the nth frame you'll have a grayscale image with the object that moved. The object has to be different from the background color or it will disappear...