I'm using a Wiimote controller as an input device.
I'm using this wrapper for HID calls / polling.
In the demo scene that comes with this wrapper, polling the controller is done in the Update event.
In many Wii games aiming extremely up and down quickly triggers an action.
The wrapper indicates extreme vertical aiming positions (where the aim goes out of scope / is "offscreen") as
Y=-1
I tried to detect such a rapid up-down movements by
1) Detecting if aim is off-screen
2) If yes, have a look if the aim is within the screen again
3) Detect if aim is off-screen again and if all this happened in a certain time period
The problem however is (I think due to the nature of polling only in the Update event), #2) doesn't necessarily have to occur. It's possible that the aim was in the screen, but the controller wasn't polled when it was.
I would like to ask what might be a valid solution to this problem.
Your polling would have to be pretty bad for this to be an issue, but other than increasing the poll rate, there isn't really anything you can do here.
The only other option would be to use the gyroscope or accelerometer instead (sorry, didn't bother to check if your wrapper exposes those). You could essentially combine a harsh vertical shake with the point being off screen, but if your polling is an issue in the original solution, it will still probably be an issue here too.
I am trying to detect how hard someone is pushing the wp7 screen for a drawing application. Is there a way to detect how big surface area is where the screen is being touched. I reckon that would be a reasonably accurate way to determine how hard the screen is being touched - A light touch would have a small touch surface area while a hard press would have a bigger touch area.
Has anyone ever tried something like this?
You can determine this with a very simple equation.
Pressure = Force / Area
To solve this, you would need to know at least two of the variables. Suppose you can find the area from the phone's sensors. You would still need to know the pressure in order to calculate the force or in other words, how hard the user is pressing the screen.
Hope this helps you!
I'm making a game in XNA and currently I'm checking the coordinates of the mouse click against the coordinates of each object that can be clicked.
This is fine for my small game but for larger games it would become CPU intensive to check through every object for each frame.
Is there a better way to approach this?
You will want to partition your world space with some sort of algorithm like Quadtree.
In your most basic form you'll want to be able to take all objects and be able to quickly throw out a bunch of them before you even do your detailed check. For instance, if you are clicking on the right side of the screen you want to throw out everything on the left side of the screen automagically.
I'm doing a kinect Application using Official Kinect SDK.
The Result I want
1) able to identify the body have been waving for 5sec. Do something if it does
2) able to identify leaning with one leg for 5sec. do something if it does.
Anyone knows how to do so? I'm doing in a WPF application.
Would like to have some example. I'm rather new to Kinect.
Thanks in advance for all your help!
The Kinect provides you with the skeletons it's tracking, you have to do the rest. Basically you need to create a definition for each gesture you want, and run that against the skeletons every time the SkeletonFrameReady event is fired. This isn't easy.
Defining Gestures
Defining the gestures can be surprisingly difficult. The simplest (easiest) gestures are ones that happen at a single point in time, and therefore don't rely on past locations of the limbs. For example, if you want to detect when the user has their hand raised above their head, this can be checked on every individual frame. More complicated gestures need to take a period of time into account. For your waving gesture, you won't be able to tell from a single frame whether a person is waving or just holding their hand up in front of them.
So now you need to be able to store relevant information from the past, but what information is relevant? Should you keep a store of the last 30 frames and run an algorithm against that? 30 frames only gets you a second's worth of information.. perhaps 60 frames? Or for your 5 seconds, 300 frames? Humans don't move that fast, so maybe you could use every fifth frame, which would bring your 5 seconds back down to 60 frames. A better idea would be to pick and choose the relevant information out of the frames. For a waving gesture the hand's current velocity, how long it's been moving, how far it's moved, etc. could all be useful information.
After you've figured out how to get and store all the information pertaining to your gesture, how do you turn those numbers into a definition? Waving could require a certain minimum speed, or a direction (left/right instead of up/down), or a duration. However, this duration isn't the 5 second duration you're interested in. This duration is the absolute minimum required to assume that the user is waving. As mentioned above, you can't determine a wave from one frame. You shouldn't determine a wave from 2, or 3, or 5, because that's just not enough time. If my hand twitches for a fraction of a second, would you consider that a wave? There's probably a sweet spot where most people would agree that a left to right motion constitutes a wave, but I certainly don't know it well enough to define it in an algorithm.
There's another problem with requiring a user to do a certain gesture for a period of time. Chances are, not every frame in that five seconds will appear to be a wave, regardless of how well you write the definition. Where as you can easily determine if someone held their hand over their head for five seconds (because it can be determined on a single frame basis), it's much harder to do that for complicated gestures. And while waving isn't that complicated, it still shows this problem. As your hand changes direction at either side of a wave, it stops moving for a fraction of a second. Are you still waving then? If you answered yes, wave more slowly so you pause a little more at either side. Would that pause still be considered a wave? Chances are, at some point in that five second gesture, the definition will fail to detect a wave. So now you need to take into account a leniency for the gesture duration.. if the waving gesture occurred for 95% of the last five seconds, is that good enough? 90%? 80%?
The point I'm trying to make here is there's no easy way to do gesture recognition. You have to think through the gesture and determine some kind of definition that will turn a bunch of joint positions (the skeleton data) into a gesture. You'll need to keep track of relevant data from past frames, but realize that the gesture definition likely won't be perfect.
Consider the Users
So now that I've said why the five second wave would be difficult to detect, allow me to at least give my thoughts on how to do it: don't. You shouldn't force users to repeat a motion based gesture for a set period of time (the five second wave). It is surprisingly tiring and just not what people expect/want from computers. Point and click is instantaneous; as soon as we click, we expect a response. No one wants to have to hold a click down for five seconds before they can open Minesweeper. Repeating a gesture over a period of time is okay if it's continually executing some action, like using a gesture to cycle through a list - the user will understand that they must continue doing the gesture to move farther through the list. This even makes the gesture easier to detect, because instead of needing information for the last 5 seconds, you just need enough information to know if the user is doing the gesture right now.
If you want the user to hold a gesture for a set amount of time, make it a stationary gesture (holding your hand at some position for x seconds is a lot easier than waving). It's also a very good idea to give some visual feedback, to say that the timer has started. If a user screws up the gesture (wrong hand, wrong place, etc) and ends up standing there for 5 or 10 seconds waiting for something to happen, they won't be happy, but that's not really part of this question.
Starting with Kinect Gestures
Start small.. really small. First, make sure you know your way around the SkeletonData class. There are 20 joints tracked on each skeleton, and they each have a TrackingState. This tracking state will show whether the Kinect can actually see the joint (Tracked), if it is figuring out the joint's position based on the rest of the skeleton (Inferred), or if it has entirely abandoned trying to find the joint (NotTracked). These states are important. You don't want to think the user is standing on one leg simply because the Kinect doesn't see the other leg and is reporting a bogus position for it. Each joint has a position, which is how you know where the user is standing.. piece by piece. Become familiar with the coordinate system.
After you know the basics of how the skeleton data is reported, try for some simple gestures. Print a message to the screen when the user raises a hand above their head. This only requires comparing each hand to the Head joint and seeing if either hand is higher than the head in the coordinate plane. After you get that working, move up to something more complicated. I'd suggest trying a swiping motion (hand in front of body, moves either right to left or left to right some minimum distance). This requires information from past frames, so you'll have to think through what information to store. If you can get that working, you could try string a series of swiping gestures in a small amount of time and interpreting that as a wave.
tl;dr: Gestures are hard. Start small, build your way up. Don't make users do repetitive motions for a single action, it's tiring and annoying. Include visual feedback for duration based gestures. Read the rest of this post.
The Kinect SDK helps you get the coordinates of different joints. A gesture is nothing but change in position of a set of joints over a period of time.
To recognize gestures, you've to store the coordinates for a period of time and iterate through it to see if it obeys the rules for a particular gesture (such as - the right hand always moves upwards).
For more details, check out my blog post on the topic:
http://tinyurl.com/89o7sf5
I'm trying to implement a simple game - I've written a dial control but having trouble writing a on-screen thumbstick in Silverlight for Windows Phone - this would be a large circle - say 150px wide with a 25px circle which when held down moves round the centre much like a real thumbstick - like the Xbox 360 controller thumbsticks.
I'm finding creating this a little tricky - if there are any examples such as a Joystick one I can shrink down for example? Been trying to create something for ages and can't seem to figure it out - the centre circle is loaded from an Image and the Larger one too so it can be customised - getting the two to be within each other centred is the easy part!
As discussed, i'd suggest using XNA doing it since its considerably easier to do. With Mango you could combine XNA and Silverlight and therefore satisfy your needs for some Silverlight too.
Look at this example:
http://create.msdn.com/en-US/sample/touchthumbsticks
It shows how to easily create a thumbstick control. To restrict the area which you can touch, just create a new Rectangle at the position of the thumbstick with the size you desire and use the .Contains(...) overload to check if the position of the tap is inside it and then act accordingly (update the stick, or ignore input).
Check out the .Contains(...) function and its overloads:
http://msdn.microsoft.com/de-de/library/microsoft.xna.framework.rectangle.contains.aspx
I have learned that many programmers tend to stick to Silverlight for they think XNA is some kind of holy grail and is complex to program. It is not. It just needs a bit of getting used to, but you will surely enjoy the ride to XNA enlightment. I can tell, i did :) It's fun! Just trust a stranger on the internet!
If you need to stick to Silverlight and Pre-Mango, i fear i can offer nothing of value for you, and i fear you will suffer pain in trying to recreate the same functionality XNA already offers programmers for no charge.