Quite a simple question, with continuous collision detection do I need to check both entities if they're both moving or just the fastest one of the two? I was thinking only the fastest of the two need checking but I'm not so sure if that's right. Any clarification would be great.
Thanks
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So.
After many years of iOS development I said it's time to try to do a little game for myself. Now I chose to do it using Apple's SceneKit since it looks like it provides everything I need.
My problem is that I've stumbled upon a huge problem (for me) and searching on Google doesn't yeld any results.
Any idea how do I go about having an object (a sphere for that matter) that deforms itself, say, because of a gravitational force. So basically it should squash on impact with the ground.
Or, how do I go about deforming it when it collides with other spheres, like a soft beach ball would?
Any starting point along those lines would be helpful.
I can post my code here, but I'm afraid it has nothing to do with my problem since I really don't know where to start.
Thanks!
Update
After doing a bit more reading I think that what I want could be doable with Vertex Shaders. Is that a right path to follow?
For complicated animations, you'll generally be better off using a 3D modeling tool like Blender, Maya, or Cheetah3D to build the body and construct the animation. Those tools let you think at a higher level of abstraction. Then you can export that model to Collada (DAE) format and then import it into SceneKit.
https://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/Basic_Animation/Bounce has a tutorial on building a deforming, bouncing ball using Blender.
SceneKit only does physics using rigid bodies. If you want something to deform, you would have to do it yourself.
It is probably because SceneKit has no way of knowing how an object should be deformed. Should it just compress, should it compress in one direction and expand in all others to preserve it's volume, should only part of the model compress and the rest stay rigid (like the tires on a car).
What you could try is wait for a collision to occur and do the following
calculate and store the velocity after the bounce
disable collision checking on the object
run an animation for the "squash"
enable collision checking on the object
apply the calculated velocity
It will be entirely up to you how real or cartoony you want to make the bounce look.
Is it possible to compare two intensity histograms (derived from gray-scale images) and obtain a likeness factor? In other words, I'm trying to detect the presence or absence of an soccer ball in an image. I've tried feature detection algorithms (such as SIFT/SURF) but they are not reliable enough for my application. I need something very reliable and robust.
Many thanks for your thoughts everyone.
This answer (Comparing two histograms) might help you. Generally, intensity comparisons are quite sensitive as e.g. white during day time is different from white during night time.
I think you should be able to derive something from compareHist() in openCV (http://docs.opencv.org/doc/tutorials/imgproc/histograms/histogram_comparison/histogram_comparison.html) to suit your needs if compareHist() does fit your purpose.
If not, this paper http://www.researchgate.net/publication/222417618_Tracking_the_soccer_ball_using_multiple_fixed_cameras/file/32bfe512f7e5c13133.pdf
tracks the ball from multiple cameras and you might get some more ideas from that even though you might not be using multiple cameras.
As kkuilla have mentioned, there is an available method to compare histogram, such as compareHist() in opencv
But I am not certain if it's really applicable for your program. I think you will like to use HoughTransfrom to detect circles.
More details can be seen in this paper:
https://files.nyu.edu/jb4457/public/files/research/bristol/hough-report.pdf
Look for the part with coins for the circle detection in the paper. I did recall reading up somewhere before of how to do ball detection using Hough Transform too. Can't find it now. But it should be similar to your soccer ball.
This method should work. Hope this helps. Good luck(:
intend to programme navigating an iPad App with head motions (originally hand motions, but hands seem to difficult to detect at the moment): left, right, up and down. So I plan to use openCV and either detect the optical flow of the head area, or detect the ears and head of the user with haar cascades (openCV is delivered with quite precise head and ear xmls). Can anyone offer some advice on which solution to use? Will one of the mentioned need more power? Ear and head detection might be easier to programme? I would like to avoid to much effort in the wrong direction and don't have much expertise in my current surroundings...
thank you for any help, advice, ideas!
I would suggest to use Haar cascades because optical flow is more expensive in computing time!
Is using the native face detection in iOS 5 not an option for what you want?
I'm thinking outside the box here, but I've been with OpenCV before and it still hurts..
http://maniacdev.com/2011/11/tutorial-easy-face-detection-with-core-image-in-ios-5/
*The idea of course, being that you apply this to live input somehow
One way could be using Hidden Markov Models. There is a lot of research material(working prototypes) on how to use HMMs to recognize head gestures.
I believe ear haar classifiers are not that effective with cluttered background. Please let us know if you've got it to work!
Can anyone point me to a robust motion detection sample/implementation? I know EMGU has a motion detection sample, but its not very good, even small changes in light will be falsely detected as motion. I don't need to track objects. I am looking for a way to detect motion in a video that will not be falsely triggered by changing light conditions.
Have a look at AForge. Everything you should need is there (though you'll need to spend some time putting it all together), and it has a robust community if you need specific help.
I concur with nizmahone. use Aforge:
Here is a link with soem motiond etection in C#:
http://www.codeproject.com/KB/audio-video/Motion_Detection.aspx
thanks for taking the time to read my question.
I'm writing a 2d top-down shooter game. It is currently using Box2d as a physics engine. The thing is, it isn't really using Box2d to it's fullest potential, just for collision detection and the underlying velocity/rotation update loop. Any plans to add real physics would simply be eye-candy, not a game changer.
Now I chose Box2d because I went through 2 other physics engines, and they just couldn't handle the types of collisions I'm detecting. I'm creating several 'bullets' with very high velocities, and I do not want them to be instant hits on their targets. JigLib and Flixel both had the same problem - bullets were not overlapping enemies at the time of the frame update, and thus were not detected as collisions (i.e. the bullets passed through enemies because they moved to fast).
I moved to Box2d because of it's iterative collision sampling, as well as the SetAsBullet method on bodies. And it works great! But now Box2d is giving me troubles too - generating several bullets per second, or at the same time, is severely lowering my fps.
So I removed Box2d to confirm that it was not a rendering limitation... added my own velocity/rotation system, and I can fire hundreds of bullets per second. Great! But its lacking any sort of collision detection.
So the questions:
1) Should I write my own iterative collision engine?
2) Should I give Box2d a try again, perhaps with some tweaks to make adding new bodies faster?
3) Is there some other alternative, maybe a lightweight physics engine that specializes in this?
4) Do you know of any other techniques or design patterns that could be of use?
Thanks so much for your help!
Edit: I should note, there are not just bullets, but larger, slower projectiles as well. I considered ray casting a line segment to the projectile's previous position, and catching intersections, but that won't work for the larger objects :(
It depends on how complex your situation can become, If you are good at math and physics you can rollout a fast engine that can handle simple collisions more faster than you can learn using box2d, but why should anyone invent the bycicle if there are plenty of them already invented so choose one you like a try using it, i recommend using box2d