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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "SDL.h"
#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480
// compile with: gcc -o joymodel -std=c99 -I/usr/include/SDL -lSDL -lpthread -lm joymodel.c
static void DrawLine(SDL_Surface *screen, int x1, int y1, int x2, int y2, int color)
{
// Bresenham's line algorithm
int itmp;
const int steep = (abs(y2 - y1) > abs(x2 - x1)) ? 1 : 0;
if(steep)
{
itmp = x1; x1 = y1; y1 = itmp;
itmp = x2; x2 = y2; y2 = itmp;
}
if(x1 > x2)
{
itmp = x1; x1 = x2; x2 = itmp;
itmp = y1; y1 = y2; y2 = itmp;
}
const int dx = x2 - x1;
const int dy = abs(y2 - y1);
float error = dx / 2.0f;
const int ystep = (y1 < y2) ? 1 : -1;
int y = y1;
SDL_Rect pix_area;
for (int x = x1; x <= x2; x++)
{
if(steep)
{
pix_area.x = y;
pix_area.y = x;
}
else
{
pix_area.x = x;
pix_area.y = y;
}
pix_area.w = 1;
pix_area.h = 1;
SDL_FillRect(screen, &pix_area, color);
error -= dy;
if (error < 0)
{
y += ystep;
error += dx;
}
}
}
static int compareDoubles(const void *p1, const void *p2)
{
double d1 = *((double *) p1);
double d2 = *((double *) p2);
if (d1 < d2)
return -1;
else if (d1 > d2)
return 1;
else
return 0;
}
void WatchJoystick(SDL_Joystick *joystick)
{
SDL_Surface *screen;
const char *name;
int i, done;
SDL_Event event;
int x, y, draw;
SDL_Rect axis_area[2];
/* Set a video mode to display joystick axis position */
screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, 16, 0);
if ( screen == NULL ) {
fprintf(stderr, "Couldn't set video mode: %s\n",SDL_GetError());
return;
}
/* Print info about the joystick we are watching */
name = SDL_JoystickName(SDL_JoystickIndex(joystick));
printf("Watching joystick %d: (%s)\n", SDL_JoystickIndex(joystick),
name ? name : "Unknown Joystick");
printf("Joystick has %d axes, %d hats, %d balls, and %d buttons\n",
SDL_JoystickNumAxes(joystick), SDL_JoystickNumHats(joystick),
SDL_JoystickNumBalls(joystick),SDL_JoystickNumButtons(joystick));
/* Initialize drawing rectangles */
memset(axis_area, 0, (sizeof axis_area));
draw = 0;
double dMaxR = 0;
double dRmaxByAngle[1024];
int iNonZeroValues = 0;
for (i = 0; i < 1024; i++)
dRmaxByAngle[i] = 0.0;
/* Loop, getting joystick events! */
done = 0;
while ( ! done )
{
while ( SDL_PollEvent(&event) )
{
switch (event.type)
{
case SDL_JOYAXISMOTION:
if (event.jaxis.axis >= 0 && event.jaxis.axis <= 1)
{
double dX = (float) SDL_JoystickGetAxis(joystick, 0) / 32767.0;
double dY = (float) SDL_JoystickGetAxis(joystick, 1) / 32767.0;
double dR = sqrt(dX * dX + dY * dY);
if (dR > dMaxR) dMaxR = dR;
if (dR > 0.5)
{
// calculate 10-bit angle
double dAngle = 0.0;
if (dX == 0.0)
{
if (dY < 0.0)
dAngle = 256;
else
dAngle = 768;
}
else if (dX > 0.0)
{
dAngle = atan(-dY/dX) * 512.0 / 3.1415926535797;
if (dAngle < 0.0)
dAngle += 1024.0;
}
else
{
dAngle = atan(-dY/dX) * 512.0 / 3.1415926535797 + 512.0;
}
//printf("Radius: %.2lf Angle: %.2lf (%lf, %lf)\n", dR, dAngle, dX, dY);
int iAngle = (int) dAngle;
if (dRmaxByAngle[iAngle] == 0.0f)
{
iNonZeroValues++;
printf("non-zero values: %i\n", iNonZeroValues);
if (iNonZeroValues == 800) // fixme 850
done = 1;
}
if (dR > dRmaxByAngle[iAngle])
dRmaxByAngle[iAngle] = dR;
}
}
break;
case SDL_KEYDOWN:
if ( event.key.keysym.sym != SDLK_ESCAPE )
{
break;
}
/* Fall through to signal quit */
case SDL_QUIT:
done = 1;
break;
default:
break;
}
}
/* Erase previous axes */
SDL_FillRect(screen, &axis_area[draw], 0x0000);
/* Draw the X/Y axis */
draw = !draw;
x = (((int)SDL_JoystickGetAxis(joystick, 0))+32768);
x *= SCREEN_WIDTH;
x /= 65535;
if ( x < 0 ) {
x = 0;
} else
if ( x > (SCREEN_WIDTH-16) ) {
x = SCREEN_WIDTH-16;
}
y = (((int)SDL_JoystickGetAxis(joystick, 1))+32768);
y *= SCREEN_HEIGHT;
y /= 65535;
if ( y < 0 ) {
y = 0;
} else
if ( y > (SCREEN_HEIGHT-16) ) {
y = SCREEN_HEIGHT-16;
}
axis_area[draw].x = (Sint16)x;
axis_area[draw].y = (Sint16)y;
axis_area[draw].w = 16;
axis_area[draw].h = 16;
SDL_FillRect(screen, &axis_area[draw], 0xFFFF);
SDL_UpdateRects(screen, 2, axis_area);
}
if (iNonZeroValues >= 800)
{
/* Erase previous axes */
SDL_FillRect(screen, &axis_area[draw], 0x0000);
// normalize the radii values
printf("Maximum radius = %.3lf (16-bit: %i)\n", dMaxR, (int) (dMaxR * 32768));
for (int x = 0; x < 1024; x++)
{
dRmaxByAngle[x] /= dMaxR;
}
// divide circle into octants
double dCoefA[8], dCoefB[8], dCoefC[8];
for (int oct = 0; oct < 8; oct++)
{
const int startX = oct * 128;
const int stopX = startX + 128;
// pre-process the Rmax data by throwing out all of the non-0 points which are below the mean in any of the encompassing 16-point windows
double dRmaxWindow[16], dRmaxSum = 0.0;
int iXWindow[16];
int windHead = 0, windTail=0;
for (x = startX; x < stopX; x++)
{
// new point?
const double dNewPoint = dRmaxByAngle[x];
if (dNewPoint == 0.0)
continue;
// remove old point falling out of window
if (windHead-windTail == 16)
{
dRmaxSum -= dRmaxWindow[windTail & 15];
windTail++;
}
// add new point
dRmaxWindow[windHead & 15] = dNewPoint;
iXWindow[windHead & 15] = x;
dRmaxSum += dNewPoint;
windHead++;
// cull the herd
if (windHead - windTail == 16)
{
double dAverage = dRmaxSum / 16.0;
for (int i = 2; i < 14; i++)
{
if (dRmaxWindow[i] < dAverage)
{
dRmaxByAngle[iXWindow[i]] = 0.0;
}
}
}
}
// pre-process the Rmax data by throwing out all of the points that are less than the median
/*
double dOctantSorted[128];
for (x = startX; x < stopX; x++)
{
dOctantSorted[x-startX] = dRmaxByAngle[x];
}
qsort(dOctantSorted, 128, sizeof(double), compareDoubles);
for (x = 0; x < 128; x++)
if (dOctantSorted[x] > 0.0)
break;
double dRmaxMedian = dOctantSorted[(x+128)/2];
for (x = startX; x < stopX; x++)
{
if (dRmaxByAngle[x] < dRmaxMedian)
dRmaxByAngle[x] = 0.0;
}
*/
// calculate least-squares quadratic regression fit
double dS[5][2];
for (int i = 0; i < 2; i++)
for (int j = 0; j < 5; j++)
dS[j][i] = 0.0;
double dYSum = 0.0;
int N = 0;
for (x = startX; x < stopX; x++)
{
if (dRmaxByAngle[x] > 0.0)
{
dYSum += dRmaxByAngle[x];
N++;
}
}
const double dYMean = dYSum / N;
for (x = startX; x < stopX; x++)
{
double dX = (x - startX) / 128.0;
double dY = dRmaxByAngle[x];
if (dY > 0.0)
{
dY -= dYMean;
dS[0][0] += 1.0;
dS[1][0] += dX;
dS[2][0] += dX * dX;
dS[3][0] += dX * dX * dX;
dS[4][0] += dX * dX * dX * dX;
dS[0][1] += dY;
dS[1][1] += dX * dY;
dS[2][1] += dX * dX * dY;
}
}
/* Here's one way to do it
double dDenom2 = (dS[0][0] * dS[2][0] * dS[4][0] - pow(dS[1][0],2) * dS[4][0] - dS[0][0] * pow(dS[3][0],2) + 2 * dS[1][0] * dS[2][0] * dS[3][0] - pow(dS[2][0],3));
double dA2 = (dS[0][1] * dS[1][0] * dS[3][0] - dS[1][1] * dS[0][0] * dS[3][0] - dS[0][1] * pow(dS[2][0],2)
+ dS[1][1] * dS[1][0] * dS[2][0] + dS[2][1] * dS[0][0] * dS[2][0] - dS[2][1] * pow(dS[1][0],2)) / dDenom2;
double dB2 = (dS[1][1] * dS[0][0] * dS[4][0] - dS[0][1] * dS[1][0] * dS[4][0] + dS[0][1] * dS[2][0] * dS[3][0]
- dS[2][1] * dS[0][0] * dS[3][0] - dS[1][1] * pow(dS[2][0],2) + dS[2][1] * dS[1][0] * dS[2][0]) / dDenom2;
double dC2 = (dS[0][1] * dS[2][0] * dS[4][0] - dS[1][1] * dS[1][0] * dS[4][0] - dS[0][1] * pow(dS[3][0],2)
+ dS[1][1] * dS[2][0] * dS[3][0] + dS[2][1] * dS[1][0] * dS[3][0] - dS[2][1] * pow(dS[2][0],2)) / dDenom2 + dYMean;
printf("Least-squares fit for %03i - %03i degrees: A=%.3lf B=%.3lf C=%.3lf\n", oct*45, oct*45+45, dA2, dB2, dC2);
*/
/* Here's another */
double dSxx = dS[2][0] - dS[1][0] * dS[1][0] / dS[0][0];
double dSxy = dS[1][1] - dS[1][0] * dS[0][1] / dS[0][0];
double dSxx2 = dS[3][0] - dS[1][0] * dS[2][0] / dS[0][0];
double dSx2y = dS[2][1] - dS[2][0] * dS[0][1] / dS[0][0];
double dSx2x2 = dS[4][0] - dS[2][0] * dS[2][0] / dS[0][0];
double dDenom = dSxx * dSx2x2 - dSxx2 * dSxx2;
double dA = (dSx2y * dSxx - dSxy * dSxx2) / dDenom;
double dB = (dSxy * dSx2x2 - dSx2y * dSxx2) / dDenom;
double dC = dS[0][1] / dS[0][0] - dB * dS[1][0] / dS[0][0] - dA * dS[2][0] / dS[0][0] + dYMean;
printf("Least-squares fit for %03i - %03i degrees: A=%.3lf B=%.3lf C=%.3lf\n", oct*45, oct*45+45, dA, dB, dC);
dCoefA[oct] = dA;
dCoefB[oct] = dB;
dCoefC[oct] = dC;
// draw the points
for (x = startX; x < stopX; x++)
{
if (dRmaxByAngle[x] == 0.0)
continue;
int pixX = (int) ((0.5 * dRmaxByAngle[x] * cos(x * 3.14159265 / 512) + 0.5) * SCREEN_HEIGHT);
int pixY = (int) ((0.5 * dRmaxByAngle[x] * -sin(x * 3.14159265 / 512) + 0.5) * SCREEN_HEIGHT);
if (pixY < 1) pixY = 1;
if (pixY > SCREEN_HEIGHT-2) pixY = SCREEN_HEIGHT-2;
axis_area[0].x = pixX - 1;
axis_area[0].y = pixY - 1;
axis_area[0].w = 3;
axis_area[0].h = 3;
SDL_FillRect(screen, &axis_area[0], 0xF800);
}
// draw the curve
for (x = startX; x < stopX; x += 4)
{
double dX0 = (x - startX) / 128.0;
double dX1 = dX0 + (4.0 / 128.0);
double dR0 = (dA*dX0*dX0 + dB*dX0 + dC);
double dR1 = (dA*dX1*dX1 + dB*dX1 + dC);
int lineX0 = (int) ((0.5 * dR0 * cos(x * 3.14159265 / 512) + 0.5) * SCREEN_HEIGHT);
int lineY0 = (int) ((0.5 * dR0 * -sin(x * 3.14159265 / 512) + 0.5) * SCREEN_HEIGHT);
int lineX1 = (int) ((0.5 * dR1 * cos((x+4) * 3.14159265 / 512) + 0.5) * SCREEN_HEIGHT);
int lineY1 = (int) ((0.5 * dR1 * -sin((x+4) * 3.14159265 / 512) + 0.5) * SCREEN_HEIGHT);
DrawLine(screen, lineX0, lineY0, lineX1, lineY1, 0xffff);
}
// refresh the screen
SDL_UpdateRect(screen, 0, 0, 0, 0);
}
// find the octant with the maximum area under the curve
int iBigOct[2] = { -1, -1 };
double dBigArea[2] = { 0.0, 0.0 };
for (int oct = 0; oct < 8; oct++)
{
double dArea = (dCoefA[oct] / 3.0) + (dCoefB[oct] / 2.0) + dCoefC[oct];
if (iBigOct[oct&1] == -1 || dArea > dBigArea[oct&1])
{
iBigOct[oct&1] = oct;
dBigArea[oct&1] = dArea;
}
}
printf("Octants %i and %i have the most area\n", iBigOct[0], iBigOct[1]);
// draw this curve in blue on each octant
double dHardA[2] = { 0.250, 0.228 };
double dHardB[2] = { -0.115, -0.361 };
double dHardC[2] = { 0.867, 1.000 };
for (int oct = 0; oct < 8; oct++)
{
const int startX = oct * 128;
const int stopX = startX + 128;
// draw the curve
//const double dA = dCoefA[iBigOct[oct&1]];
//const double dB = dCoefB[iBigOct[oct&1]];
//const double dC = dCoefC[iBigOct[oct&1]];
const double dA = dHardA[oct&1];
const double dB = dHardB[oct&1];
const double dC = dHardC[oct&1];
for (x = startX; x < stopX; x += 4)
{
double dX0 = (x - startX) / 128.0;
double dX1 = dX0 + (4.0 / 128.0);
double dR0 = (dA*dX0*dX0 + dB*dX0 + dC);
double dR1 = (dA*dX1*dX1 + dB*dX1 + dC);
int lineX0 = (int) ((0.5 * dR0 * cos(x * 3.14159265 / 512) + 0.5) * SCREEN_HEIGHT);
int lineY0 = (int) ((0.5 * dR0 * -sin(x * 3.14159265 / 512) + 0.5) * SCREEN_HEIGHT);
int lineX1 = (int) ((0.5 * dR1 * cos((x+4) * 3.14159265 / 512) + 0.5) * SCREEN_HEIGHT);
int lineY1 = (int) ((0.5 * dR1 * -sin((x+4) * 3.14159265 / 512) + 0.5) * SCREEN_HEIGHT);
DrawLine(screen, lineX0, lineY0, lineX1, lineY1, 0x001f);
}
}
// refresh the screen
SDL_UpdateRect(screen, 0, 0, 0, 0);
// wait for keypress
while (1)
{
if (SDL_PollEvent(&event))
{
if (event.type == SDL_KEYDOWN)
break;
}
SDL_Delay(10);
}
}
}
int main(int argc, char *argv[])
{
const char *name;
int i;
SDL_Joystick *joystick;
/* Initialize SDL (Note: video is required to start event loop) */
if ( SDL_Init(SDL_INIT_VIDEO|SDL_INIT_JOYSTICK) < 0 ) {
fprintf(stderr, "Couldn't initialize SDL: %s\n",SDL_GetError());
exit(1);
}
/* Print information about the joysticks */
printf("There are %d joysticks attached\n", SDL_NumJoysticks());
for ( i=0; i<SDL_NumJoysticks(); ++i ) {
name = SDL_JoystickName(i);
printf("Joystick %d: %s\n",i,name ? name : "Unknown Joystick");
joystick = SDL_JoystickOpen(i);
if (joystick == NULL) {
fprintf(stderr, "SDL_JoystickOpen(%d) failed: %s\n", i, SDL_GetError());
} else {
printf(" axes: %d\n", SDL_JoystickNumAxes(joystick));
printf(" balls: %d\n", SDL_JoystickNumBalls(joystick));
printf(" hats: %d\n", SDL_JoystickNumHats(joystick));
printf(" buttons: %d\n", SDL_JoystickNumButtons(joystick));
SDL_JoystickClose(joystick);
}
}
if ( argv[1] ) {
joystick = SDL_JoystickOpen(atoi(argv[1]));
if ( joystick == NULL ) {
printf("Couldn't open joystick %d: %s\n", atoi(argv[1]),
SDL_GetError());
} else {
WatchJoystick(joystick);
SDL_JoystickClose(joystick);
}
}
SDL_QuitSubSystem(SDL_INIT_VIDEO|SDL_INIT_JOYSTICK);
return(0);
}
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