I'm looking at the aurioTouch sample application for the iPhone SDK. It has a basic spectrum analyzer implemented when you choose the "FFT" option. One of the things the app is lacking is X axis labels (i.e. the frequency labels).
In the aurioTouchAppDelegate.mm file, in the function - (void)drawOscilloscope at line 652, it has the following code:
if (displayMode == aurioTouchDisplayModeOscilloscopeFFT)
{
if (fftBufferManager->HasNewAudioData())
{
if (fftBufferManager->ComputeFFT(l_fftData))
[self setFFTData:l_fftData length:fftBufferManager->GetNumberFrames() / 2];
else
hasNewFFTData = NO;
}
if (hasNewFFTData)
{
int y, maxY;
maxY = drawBufferLen;
for (y=0; y<maxY; y++)
{
CGFloat yFract = (CGFloat)y / (CGFloat)(maxY - 1);
CGFloat fftIdx = yFract * ((CGFloat)fftLength);
double fftIdx_i, fftIdx_f;
fftIdx_f = modf(fftIdx, &fftIdx_i);
SInt8 fft_l, fft_r;
CGFloat fft_l_fl, fft_r_fl;
CGFloat interpVal;
fft_l = (fftData[(int)fftIdx_i] & 0xFF000000) >> 24;
fft_r = (fftData[(int)fftIdx_i + 1] & 0xFF000000) >> 24;
fft_l_fl = (CGFloat)(fft_l + 80) / 64.;
fft_r_fl = (CGFloat)(fft_r + 80) / 64.;
interpVal = fft_l_fl * (1. - fftIdx_f) + fft_r_fl * fftIdx_f;
interpVal = CLAMP(0., interpVal, 1.);
drawBuffers[0][y] = (interpVal * 120);
}
cycleOscilloscopeLines();
}
}
From my understanding, this part of the code is what is used to decide which magnitude to draw for each frequency in the UI. My question is how can I determine what frequency each iteration (or y value) represents inside the for loop.
For example, if I want to know what the magnitude is for 6kHz, I'm thinking of adding a line similar to the following:
if (yValueRepresentskHz(y, 6))
NSLog(#"The magnitude for 6kHz is %f", (interpVal * 120));
Please note that although they chose to use the variable name y, from what I understand, it actually represents the x-axis in the visual graph of the spectrum analyzer, and the value of the drawBuffers[0][y] represents the y-axis.
I believe that the frequency of each bin it is using is given by
yFract * hwSampleRate * .5
I'm fairly certain that you need the .5 because yFract is a fraction of the total fftLength and the last bin of the FFT corresponds with half of the sampling rate. Thus, you could do something like
NSLog(#"The magnitude for %f Hz is %f.", (yFract * hwSampleRate * .5), (interpVal * 120));
Hopefully that helps to point you in the right direction at least.
Related
I want to throw a ball that has a projectile motion. I have a monkey on centre of screen and onTouchBegin I am taking the starting point of the touch and onTouchEnded I am taking the ending points. From the starting and ending points I am taking the angle value between them. Like 30 degrees, 45 or 90 degree.
This is my code by which I have calculated angle of start to endpoint
float angleRadians = atan2(startTouchPoint.x - touchPoint.x, startTouchPoint.y - touchPoint.y);
float angleDegrees = CC_RADIANS_TO_DEGREES(angleRadians);
float cocosAngle = -1 * angleDegrees;
Now i am using Projectile motion formula to throw ball with angle i have calculated from above formula .
inside init method
gravity = 9.8; // metres per second square
X = 0;
Y = 0;
V0 = 50; // meters per second -- elevation
VX0 = V0 * cos(angle); // meters per second
VY0 = V0 * sin(angle); // meters per second
gameTime = 0;
and onTouchEnded i have called fire method which will throw ball .
-(void)fire:(ccTime) dt
{
CCLOG(#"Angle 1: %.2f",angle);
gameTime += dt*6;
// x = v0 * t * cos(angle)
X = (V0 * gameTime * cos(angle))/2+120;
// y = v0 * t * sin(angle) - 0.5 * g * t^2
Y = (V0 * gameTime * sin(angle) - 0.5 * gravity * pow(gameTime, 2))/2+255;
if (Y > 50)
{
sprite_webfire.position = ccp(X,Y);
flag = true;
}
else
{
//angleValue += 15;
angleValue = angle;
angle = [self DegreesToRadians:angleValue];
gravity = 9.8; // metres per second square
X = 0;
Y = 0;
V0 = 50; // meters per second -- elevation
VX0 = V0 * cos(angle); // meters per second
VY0 = V0 * sin(angle); // meters per second
gameTime = 0;
// [self pauseSchedulerAndActions];
}
if (Y < 50)
{
[self unschedule:#selector(fire:)];
}
NSLog(#"ball (%lf,%lf), dt = %lf angle value %d", X, Y, dt,angleValue);
}
this code is working . by this code i can throw ball in projectile motion but i cant throw it where i want to. i cant throw wrt to given angle from start to end point.
i can throw it like red mark but i want to throw it blue mark with swipe . but its not throwing like i am swiping screen.
I am not certain on what math you are using to do this, I find your documentation a bit confusing.
Generally, for project tile motion this is what you need to do:
Find out what the take off angle is relative to the horizontal. Then depending on whatever initial velocity you want the object to have, use that and you trig equations to put your initial velocities into rectangular components.
For example:
If initial velocity was 10, the initial velocity in the y direction would be 10sin(angle), and in the x direction it would be 10cos(angle).
Then in to update the position of the sprite you should use kinematics equations: http://www.physicsclassroom.com/class/1dkin/u1l6c.cfm
First update velocities:
Velocity in the Y direction: V = v(initial) + gravity*(Delta-time)
Velocity in the X direction is constant unless you want to factor in some sort of resistance to make things a lot more complicated.
then position y = oldPositionY + velocity(in Y direction)*(Delta-time) + 1/2(gravity)(delta-time)^2.
and position x = oldPositionX + Xvelocity*delta-time
I have done some projectile motion stuff, and I have found you need to make gravity a large constant, something around 500 to make it look life-like. Let me know if this is confusing or you don't know how to implement it.
I would suggest that you take a look at the following tutorial: http://www.raywenderlich.com/4756/how-to-make-a-catapult-shooting-game-with-cocos2d-and-box2d-part-1.
It shows you how to use a physics engine, so you don't need to do much of the math. All the 'bullets' in the tutorial are also moving with projectile motion.
I'll add a bit to what was already said (which was good). Firstly, you should not be wasting time computing any angles. Stick with vectors for your velocity. In other words, get the initial velocity vector from the touch start and end location, and that will be your (v0x, v0y). For example:
CGPoint initialVelocity = ccpSub(touchPoint, startTouchPoint);
float v0x = initialVelocity.x;
float v0y = initialVelocity.y;
If you wish to assign a different magnitude to the initial velocity vector, simply normalize it and then multiply it by a new magnitude.
CGPoint unitVelocity = ccpNormalize(initialVelocity);
float magnitude = 200; // or whatever you want it to be
CGPoint velocity = ccpMult(unitVelocity, magnitude);
Anyway, with this velocity set properly you can then use it in your position calculations as before, but without the added complexity of calculating the angles.
-(void) fire:(ccTime)dt
{
.
.
gameTime += dt;
// if x(t) = x0 + v0x*t, then dx = v0x*dt
x += v0x*dt;
// if y(t) = y0 + v0y*t - 0.5t^2, then dy = v0y*dt - g*t*dt
y += (v0y * dt - g*gameTime*dt);
.
.
}
Also you should not set v0 = 50. Calculate the velocity from the vector as I suggested.
Something important to consider is that you are calculating what the movement should be in a physical world based upon units of meters. The screen is operating in points, not meters, so you will probably have to apply a scaling factor to the new position (x,y) to get the look that you are going for.
Edit: my bad, I had to revisit my math in the position calculation. My differentials was a bit rusty.
I am currently using the following code to count the number of steps a user takes in my indoor navigation application. As I am holding the phone around my chest level with the screen facing upwards, it counts the number of steps I take pretty well. But common actions like a tap on the screen or panning through the map register step counts as well. This is very frustrating as the tracking of my movement within the floor plan will become highly inaccurate. Does anyone have any idea how I can improve the accuracy of tracking in this case? Any comments will be much appreciated! To have a better idea of what I'm trying to do, you guys can check out a similar Android application at http://www.youtube.com/watch?v=wMgIa44mJXY. Thanks!
-(void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
float xx = acceleration.x;
float yy = acceleration.y;
float zz = acceleration.z;
float dot = (px * xx) + (py * yy) + (pz * zz);
float a = ABS(sqrt(px * px + py * py + pz * pz));
float b = ABS(sqrt(xx * xx + yy * yy + zz * zz));
dot /= (a * b);
if (dot <= 0.9989) {
if (!isSleeping) {
isSleeping = YES;
[self performSelector:#selector(wakeUp) withObject:nil afterDelay:0.3];
numSteps += 1;
}
}
px = xx; py = yy; pz = zz;
}
The data from the accelerometer is basically a unidimensional (time) non uniform sampling of a three dimensional vector signal. The best way to figure out how to count steps will be to write an app that records and store the samples over a certain period of time, then export the data to a mathematical application like Wolfram's Mathematica for analysis and visualization. Remember that the sampling is non uniform, you may or may not want to transform it into a uniformly sampled digital signal.
Then you can try different signal processing algorithms to see what works best.
It's possible that, once you know the basic shape of a step in accelerometer data, you can recognize them by simple convolution.
I'm trying to convert the geomagnetic and accelerometer to rotate the camera in opengl ES1, I found some code from android and changed this code for iPhone, actually it is working more or less, but there are some mistakes, I´m not able to find this mistake, I put the code, also the call to Opengl Es1: glLoadMatrixf((GLfloat*)matrix);
- (void) GetAccelerometerMatrix:(GLfloat *) matrix headingX: (float)hx headingY:(float)hy headingZ:(float)hz;
{
_geomagnetic[0] = hx * (FILTERINGFACTOR-0.05) + _geomagnetic[0] * (1.0 - FILTERINGFACTOR-0.5)+ _geomagnetic[3] * (0.55);
_geomagnetic[1] = hy * (FILTERINGFACTOR-0.05) + _geomagnetic[1] * (1.0 - FILTERINGFACTOR-0.5)+ _geomagnetic[4] * (0.55);
_geomagnetic[2] = hz * (FILTERINGFACTOR-0.05) + _geomagnetic[2] * (1.0 - FILTERINGFACTOR-0.5)+ _geomagnetic[5] * (0.55);
_geomagnetic[3]=_geomagnetic[0] ;
_geomagnetic[4]=_geomagnetic[1];
_geomagnetic[5]=_geomagnetic[2];
//Clear matrix to be used to rotate from the current referential to one based on the gravity vector
bzero(matrix, sizeof(matrix));
//MAGNETIC
float Ex = -_geomagnetic[1];
float Ey =_geomagnetic[0];
float Ez =_geomagnetic[2];
//ACCELEROMETER
float Ax= -_accelerometer[0];
float Ay= _accelerometer[1] ;
float Az= _accelerometer[2] ;
float Hx = Ey*Az - Ez*Ay;
float Hy= Ez*Ax - Ex*Az;
float Hz = Ex*Ay - Ey*Ax;
float normH = (float)sqrt(Hx*Hx + Hy*Hy + Hz*Hz);
float invH = 1.0f / normH;
Hx *= invH;
Hy *= invH;
Hz *= invH;
float invA = 1.0f / (float)sqrt(Ax*Ax + Ay*Ay + Az*Az);
Ax *= invA;
Ay *= invA;
Az *= invA;
float Mx = Ay*Hz - Az*Hy;
float My = Az*Hx - Ax*Hz;
float Mz = Ax*Hy - Ay*Hx;
// if (mOut.f != null) {
matrix[0] = Hx; matrix[1] = Hy; matrix[2] = Hz; matrix[3] = 0;
matrix[4] = Mx; matrix[5] = My; matrix[6] = Mz; matrix[7] = 0;
matrix[8] = Ax; matrix[9] = Ay; matrix[10] = Az; matrix[11] = 0;
matrix[12] = 0; matrix[13] = 0; matrix[14] = 0; matrix[15] = 1;
}
Thank you very much for the help.
Edit: The iPhone it is permantly in landscape orientation and I know that something is wrong because the object painted in Opengl Es appears two times.
Have you looked at Apple's GLGravity sample code? It does something very similar to what you want here, by manipulating the model view matrix in response to changes in the accelerometer input.
I'm unable to find any problems with the code posted, and would suggest the problem is elsewhere. If it helps, my analysis of the code posted is that:
The first six lines, dealing with _geomagnetic 0–5, effect a very simple low frequency filter, which assumes you call the method at regular intervals. So you end up with a version of the magnetometer vector, hopefully with high frequency jitter removed.
The bzero zeroes the result, ready for accumulation.
The lines down to the declaration and assignment to Hz take the magnetometer and accelerometer vectors and perform the cross product. So H(x, y, z) is now a vector at right angles to both the accelerometer (which is presumed to be 'down') and the magnetometer (which will be forward + some up). Call that the side vector.
The invH and invA stuff, down to the multiplication of Az by invA ensure that the side and accelerometer/down vectors are of unit length.
M(x, y, z) is then created, as the cross product of the side and down vectors (ie, a vector at right angles to both of those). So it gives the front vector.
Finally, the three vectors are used to populate the matrix, taking advantage of the fact that the inverse of an orthonormal 3x3 matrix is its transpose (though that's sort of hidden by the way things are laid out — pay attention to the array indices). You actually set everything in the matrix directly, so the bzero wasn't necessary in pure outcome terms.
glLoadMatrixf is then the correct thing to use because that's how you multiply by an arbitrary column-major matrix in OpenGL ES 1.x.
I have been using the Hough transform in my application both using Matlab and OpenCV/labview and found that for some images, the hough transform gave an obviously wrong line fit (consistently)
Here are the test and overlayed images. The angle seem right, but the rho is off.
On the image below, you will see the top image tries to fit a line to the left side of the original image and the bottom image fits a line to the right side of the image.
In Matlab, I call the Hough function through
[H1D,theta1D,rho1D] = hough(img_1D_dilate,'ThetaResolution',0.2);
in C++, i trimmed the OpenCV HoughLines function so I end up with only the part we are filling the accumulator. Note that because my theta resolution is 0.2, I have 900 angles to analyze. The tabSin and tabCos are defined prior to the function so that they are just a sin and cos of the angle.
Note that these routines generally work well, but just for specific cases it performs the way I have shown.
double start_angle = 60.0;
double end_angle = 120.0;
double num_theta = 180;
int start_ang = num_theta * start_angle/180;
int end_ang = num_theta * end_angle/180;
int i,j,n,index;
for (i = 0;i<numrows;i++)
{
for (j = 0;j<numcols;j++)
{
if (img[i*numcols + j] == 100)
{
for (n = 0;n<180;n++)
{
index = cvRound((j*tabCos[n] + i * tabSin[n])) + (numrho-1)/2;
accum[(n+1) * (numrho+2) + index+1]++;
}
}
}
}
TabCos and tabSin are defined in Labview with this code
int32 i;
float64 theta_prec;
float64 tabSin[180];
float64 tabCos[180];
theta_prec = 1/180*3.14159;
for (i = 0;i<180;i++)
{
tabSin[i] = sin(itheta_prec);
tabCos[i] = cos(itheta_prec);
}
any suggestions would be greatly appreciated
I guess i'll put down the answer to this problem.
I was converting the rho and theta into m and b, then computing the values of x and y from the m and b. I believe this may have caused some precision error somewhere.
this error was fixed by obtaining x and y directly from rho and theta rather than going through m and b.
the function is
y = -cos(theta)/sin(theta)*x + rho/sin(theta);
I've tried several ways of measuring the steps a user makes with an iPhone by reading the accelerometer, but none have been very accurate. The most accurate implementation I've used is the following:
float xx = acceleration.x;
float yy = acceleration.y;
float zz = acceleration.z;
float dot = (mOldAccX * xx) + (mOldAccY * yy) + (mOldAccZ * zz);
float a = ABS(sqrt(mOldAccX * mOldAccX + mOldAccY * mOldAccY + mOldAccZ * mOldAccZ));
float b = ABS(sqrt(xx * xx + yy * yy + zz * zz));
dot /= (a * b);
if (dot <= 0.994 && dot > 0.90) // bounce
{
if (!isChange)
{
isChange = YES;
mNumberOfSteps += 1;
} else {
isChange = NO;
}
}
mOldAccX = xx;
mOldAccY = yy;
mOldAccZ = zz;
}
However, this only catches 80% of the user's steps. How can I improve the accuracy of my pedometer?
Here is some more precise answer to detect each step. But yes in my case I am getting + or - 1 step with every 25 steps. So I hope this might be helpful to you. :)
if (dot <= 0.90) {
if (!isSleeping) {
isSleeping = YES;
[self performSelector:#selector(wakeUp) withObject:nil afterDelay:0.3];
numSteps += 1;
self.stepsCount.text = [NSString stringWithFormat:#"%d", numSteps];
}
}
- (void)wakeUp {
isSleeping = NO;
}
ok, I'm assuming this code is within the addAcceleration function...
-(void)addAcceleration:(UIAcceleration*)accel
So, you could increase your sampling rate to get a finer granularity of detection. So for example, if you are currently taking 30 samples per second, you could increase it to 40, 50, or 60 etc... Then decide if you need to count a number of samples that fall within your bounce and consider that a single step. It sounds like you are not counting some steps due to missing some of the bounces.
Also, what is the purpose of toggling isChange? Shouldn't you use a counter with a reset after x number of counts? If you are within your bounce...
if (dot <= 0.994 && dot > 0.90) // bounce
you would have to hit this sweet spot 2 times, but the way you have set this up, it may not be two consecutive samples in a row, it may be a first sample and a 5th sample, or a 2nd sample and an 11th sample. That is where you are loosing step counts.
Keep in mind that not everyone makes the same big steps. So the dot calculation should be adjusted according to someone's length, step size.
You should adjust the bounce threshold accordingly. Try to make the program learn about it's passenger.