I don't know if this is the best site to ask this.
I have a camera in front of me, and I wanted to rotate my head horizontally every 10 degrees.
What is the most practical way?
I was thinking of a protractor and a wire.
Any options?
Related
I'm working on a project where I'm capturing people making free throw shots via a video camera. I need a way to detect, as fast as possible, the instant the ball is released from a player's hand. I tried researching a lot of detection/tracking algorithms, but everything I've found seemed more suited to tracking the ball itself. While I may eventually want to do that, right now all I need to know is the release timing.
I'm also open to other solutions that don't use the camera (I have a decent budget), but of course I'd like to use the camera if possible/fast enough. I'm also able to mess with the camera positioning/setup, and what I even want in the FOV.
Does anyone have any ideas? I'm pretty stuck right now, and haven't been able to find anything online that can help.
A solution is to use visual markers (motion trackers) on the throwing hands and on the ball. The precision is based on the FPS of the camera.
The assumption is that you know the ball dimension and the hand grip on the ball that may vary. By using visual markers/trackers you can know the position of the ball relative to the hand. When the distance between the initial grip of the ball and the hand is bigger than the distance between the center of the ball and it's extremity then is when you have your release. Schema of the method
A better solution is to use a graded meter bar (alternate between black and white bars like the ones used on the mythbusters show to track the speed of objects). At the moment there is a color gap between the hand and the ball you have your release. The downside of this approach is that you have to capture the image at a side angle or top-down angle and use panels to hold the grading.
Your problem is similar to the billiard ball collision detection. I hope you find this paper helpful.
Edit:
There is a powerful tool, that is not that expensive named Microsoft Kinect used for motion capture. The downside of this tool is that it's camera works with 30 fps and you cannot use it accurately on a very sunny scene. However I have found a scientific paper about using kinect to record athletes, including free-throws in basketball. Paper here
It's my first answer on so. Any feedback on how to improve my future answers is appreciated.
Currently working on a project to read the gauges on our chiller. I'm not a programmer by trade, so I'm trying to learn as I go, but SimpleCV's documentation isn't that great (IMO...)
At the moment I'm doing a findLines on each image, and it sort of works, but will occasionaly find a "line" on the edge of the gauge itself, or return some other weird result.
What I'd like to do is paint the gauge pivot one color, and the tip of the needle another color, and measure the angle between the two. I think I have the color blob detection figured out, but I can't figure out the measuring the angle part.
Anyone have any ideas? All I need is the angle to be returned, the BMS system will accept the angle reading and do the scale conversion itself, so that isn't a problem.
one of the core simplecv developers here. Sorry the docs aren't up to snuff.
I think if you can paint the gauge it will probably make it easier, or you may not even need to.
I whipped up the example here as you can see image output along the way as well:
http://nbviewer.ipython.org/github/xamox/sandbox/blob/master/gas-gauge-angle/Gauge%20Angle.ipynb
How would you do a mesh/plane (representing a tablecloth) that falls on top of a smaller cube (representing a restaurant table), so that when the tablecloth is in place its edges would hang and fold realistically over the table. It would be cool to animate this falling with physics and gravity so it would look really neat and real. I also would like to use a tileable texture (tablecloth pattern) for the tablecloth.
I am planning to make this with Three.js, but I guess any other javascript library or tool would be fine as well. At this point even a static render of the scenario would be a great starting point.
Any tips how to approach this? Thanks.
You lucked out -- it's practically done for you. :-)
http://mrdoob.github.com/three.js/examples/webgl_animation_cloth.html
What would be the best way to detect a fast moving object using OpenCV?
Say, I have 5 random video files:
1) Video of a crowd, people walking, static camera.
2) Video of a cat playing with a ball, shaky iPhone camera.
3) Video of a person being interviewed. Static camera.
4) Animation (3D) of a fast moving car, background is blurred etc. etc.
5) A blurred out video shot with iPhone camera (just camera waved around, nothing is visible).
So I would like to isolate video5 and detect that there is a lot of movement in video4 and video2.
What would be the best approach to do that? I think of using OpenCV2, but if there is a better solution for that, I'd be happy to learn about that.
Any input greatly appreciated. Pseudo-code or just recommendations of specific algorithms.
Thank you
Optical Flow This will be one of many ways of detecting motion.
I don't know if you are still on it but I found it interesting to answer.
Approach 1-
As suggested by user349026, one of the most intuitive way is to work with Optical flow, it will give you dominating motion but optical flow always comes with noises. You will have to use some filter before using the optical flow.
Approach- 2
This one difficult but gives good results.
This is from CVPR-2013 paper link- http://www.irisa.fr/texmex/people/jain/w-Flow/motion_cvpr13.pdf
I think the just introduction of this paper will solve your problem.
Ok so I have bunch of balls:
What I'm trying to figure out is how to make these circles:
Rotate based on the surfaces they are touching
Fix collision penetration when dealing with multiple touching objects.
EDIT: This is what I mean by rotation
Ball 0 will rotate anti-clockwise as it's leaning on Ball 3
Ball 5 will rotate clockwise as it's leaning on Ball 0
Even though solutions to this are universal, just for the record I'm using Javascript and SVG, and would prefer implementing this myself rather than using a library.
Help would be very much appreciated. Thanks! :)
Here are a few links I think would help you out on your quest:
Box2D
Advanced Character Physics
Javascript Ball Simulation
Box2D has what your looking for, and its open source I believe. You can download the files and see how they do what they do in order to achieve your effect.
Let me know if this helps, trying to get better at answering questions on here. :)
EDIT:
So I went ahead and thought this out just a bit more to give some insight as far as how I would approach it. Take a look at the image below:
Basically, compare the angles on a grid, if the ball is falling +30 degrees compared to the ball it falls on then rotate the ball positively. If its falling -30 degrees compared to the ball it fall on then rotate the ball negatively. Im not saying this is the correct solution, but just thinking about it, this is the way I would approach the problem off the bat.
From a physics standpoint it sounds like you want to conserve both linear and angular momentum.
As a starting point, you'll want establish ODE matrices that model both and then perform some linear algebra to solve them. I personally would use Numpy/Scipy (probably using a sparse array) for that solution. But there are many approaches (sympy comes to mind). What modules do you want to use?
You'll want to familiarize yourself with coefficient of restitution and coefficient of friction and decide if you want to conserve kinetic energy too. (do you want/care if they keep bouncing and rolling around forever?) (you'll probably need energy matrices as well)
You'll be solving these matrices every timestep all the while checking the condition that no two ball centers are closer than the sum of the two radii. (..and if they do, you adjust the momentum and energy terms for a post-collision condition)
This is just the barest of beginnings to a big project. Can I ask why you want to do this from scratch?
I would recommend checking out game physics simulation books and articles. See O'Reilly's Physics for Game Developers and the Gamasutra website, for example.