# HG changeset patch # User Holmes Futrell # Date 1216414259 0 # Node ID 7fbcfc1574dc7884c1c85a53e2071c9afae63e95 # Parent bce19d88266ca67b7ff480a5cd7b4e353b884fc9 Demo of iPhone accelerometer as SDL joystick diff -r bce19d88266c -r 7fbcfc1574dc XCodeiPhoneOS/Demos/src/accelerometer.c --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/XCodeiPhoneOS/Demos/src/accelerometer.c Fri Jul 18 20:50:59 2008 +0000 @@ -0,0 +1,225 @@ +/* + * accelerometer.c + * written by Holmes Futrell + * use however you want + */ + +#include "SDL.h" +#include "math.h" +#include "common.h" + +#define MILLESECONDS_PER_FRAME 16 /* about 60 frames per second */ +#define DAMPING 0.5f; /* after bouncing off a wall, damping coefficient determines final speed */ +#define FRICTION 0.0008f /* coefficient of acceleration that opposes direction of motion */ +#define GRAVITY_CONSTANT 0.02f /* how sensitive the ship is to the accelerometer */ + +static SDL_Joystick *accelerometer; /* used for controlling the ship */ + +static struct { + float x, y; /* position of ship */ + float vx, vy; /* velocity of ship (in pixels per millesecond) */ + SDL_Rect rect; /* (drawn) position and size of ship */ +} ship; + +static SDL_TextureID shipID=0; /* texture for spaceship */ +static SDL_TextureID spaceID=0; /* texture for space (background */ + +void render(void) { + + /* get joystick (accelerometer) axis values and normalize them */ + float amax = (float)(0x7FFF); /* largest Sint16 number */ + float ax = SDL_JoystickGetAxis(accelerometer, 0) / amax; + float ay = -SDL_JoystickGetAxis(accelerometer, 1) / amax; + + /* ship screen constraints */ + Uint32 minx = 0.0f; + Uint32 maxx = SCREEN_WIDTH - ship.rect.w; + Uint32 miny = 0.0f; + Uint32 maxy = SCREEN_HEIGHT - ship.rect.h; + + /* update velocity from accelerometer */ + ship.vx += ax * GRAVITY_CONSTANT * MILLESECONDS_PER_FRAME; + ship.vy += ay * GRAVITY_CONSTANT * MILLESECONDS_PER_FRAME; + + float speed = sqrt(ship.vx * ship.vx + ship.vy * ship.vy); + + if (speed > 0) { + /* compensate for friction */ + float dirx = ship.vx / speed; /* normalized x velocity */ + float diry = ship.vy / speed; /* normalized y velocity */ + + /* update velocity due to friction */ + if (speed - FRICTION * MILLESECONDS_PER_FRAME > 0) { + /* apply friction */ + ship.vx -= dirx * FRICTION * MILLESECONDS_PER_FRAME; + ship.vy -= diry * FRICTION * MILLESECONDS_PER_FRAME; + } + else { + /* applying friction would MORE than stop the ship, so just stop the ship */ + ship.vx = 0.0f; + ship.vy = 0.0f; + } + } + + /* update ship location */ + ship.x += ship.vx * MILLESECONDS_PER_FRAME; + ship.y += ship.vy * MILLESECONDS_PER_FRAME; + + if (ship.x > maxx) { + ship.x = maxx; + ship.vx = -ship.vx * DAMPING; + } + else if (ship.x < minx) { + ship.x = minx; + ship.vx = -ship.vx * DAMPING; + } + if (ship.y > maxy) { + ship.y = maxy; + ship.vy = -ship.vy * DAMPING; + } + else if (ship.y < miny) { + ship.y = miny; + ship.vy = -ship.vy * DAMPING; + } + + /* draw the background */ + SDL_RenderCopy(spaceID, NULL, NULL); + + /* draw the ship */ + ship.rect.x = ship.x; + ship.rect.y = ship.y; + + SDL_RenderCopy(shipID, NULL, &ship.rect); + + /* update screen */ + SDL_RenderPresent(); + +} + +void initializeTextures() { + + SDL_Surface *bmp_surface; + SDL_Surface *bmp_surface_rgba; + int format = SDL_PIXELFORMAT_ABGR8888; /* desired texture format */ + Uint32 Rmask, Gmask, Bmask, Amask; /* masks for desired format */ + int bpp; /* bits per pixel for desired format */ + + /* load the ship */ + bmp_surface = SDL_LoadBMP("ship.bmp"); + if (bmp_surface == NULL) { + fatalError("could not ship.bmp"); + } + /* set blue to transparent on the ship */ + SDL_SetColorKey(bmp_surface, 1, SDL_MapRGB(bmp_surface->format, 0, 0, 255)); + SDL_PixelFormatEnumToMasks(format, &bpp, &Rmask, &Gmask, &Bmask, &Amask); + /* + create a new RGBA surface and blit the bmp to it + this is an extra step, but it seems to be necessary for the color key to work + + does the fact that this is necessary indicate a bug in SDL? + */ + bmp_surface_rgba = SDL_CreateRGBSurface(0, bmp_surface->w, bmp_surface->h, bpp, Rmask, Gmask, Bmask, Amask); + SDL_BlitSurface(bmp_surface, NULL, bmp_surface_rgba, NULL); + + /* create ship texture from surface */ + shipID = SDL_CreateTextureFromSurface(format, bmp_surface_rgba); + if (shipID == 0) { + fatalError("could not create ship texture"); + } + SDL_SetTextureBlendMode(shipID, SDL_TEXTUREBLENDMODE_BLEND); + + /* set the width and height of the ship from the surface dimensions */ + ship.rect.w = bmp_surface->w; + ship.rect.h = bmp_surface->h; + + SDL_FreeSurface(bmp_surface_rgba); + SDL_FreeSurface(bmp_surface); + + /* load the space background */ + bmp_surface = SDL_LoadBMP("space.bmp"); + if (bmp_surface == NULL) { + fatalError("could not load space.bmp"); + } + /* create space texture from surface */ + spaceID = SDL_CreateTextureFromSurface(format, bmp_surface); + if (spaceID == 0) { + fatalError("could not create space texture"); + } + SDL_FreeSurface(bmp_surface); + +} + + + +int main(int argc, char *argv[]) { + + SDL_WindowID windowID; /* ID of main window */ + Uint32 startFrame; /* time frame began to process */ + Uint32 endFrame; /* time frame ended processing */ + Uint32 delay; /* time to pause waiting to draw next frame */ + int done; /* should we clean up and exit? */ + + /* initialize SDL */ + if (SDL_Init(SDL_INIT_VIDEO|SDL_INIT_JOYSTICK) < 0) { + fatalError("Could not initialize SDL"); + } + + /* create main window and renderer */ + windowID = SDL_CreateWindow(NULL, 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT,\ + SDL_WINDOW_OPENGL|SDL_WINDOW_SHOWN|SDL_WINDOW_BORDERLESS); + SDL_CreateRenderer(windowID, 0, 0); + + /* print out some info about joysticks and try to open accelerometer for use */ + printf("There are %d joysticks available\n", SDL_NumJoysticks()); + printf("Default joystick (index 0) is %s\n", SDL_JoystickName(0)); + accelerometer = SDL_JoystickOpen(0); + if (accelerometer == NULL) { + fatalError("Could not open joystick (accelerometer)"); + } + printf("joystick number of axis = %d\n", SDL_JoystickNumAxes(accelerometer)); + printf("joystick number of hats = %d\n", SDL_JoystickNumHats(accelerometer)); + printf("joystick number of balls = %d\n", SDL_JoystickNumBalls(accelerometer)); + printf("joystick number of buttons = %d\n", SDL_JoystickNumButtons(accelerometer)); + + /* load graphics */ + initializeTextures(); + + /* setup ship */ + ship.x = (SCREEN_WIDTH - ship.rect.w) / 2; + ship.y = (SCREEN_HEIGHT - ship.rect.h) / 2; + ship.vx = 0.0f; + ship.vy = 0.0f; + + done = 0; + /* enter main loop */ + while(!done) { + startFrame = SDL_GetTicks(); + SDL_Event event; + while (SDL_PollEvent(&event)) { + if (event.type == SDL_QUIT) { + done = 1; + } + } + render(); + endFrame = SDL_GetTicks(); + + /* figure out how much time we have left, and then sleep */ + delay = MILLESECONDS_PER_FRAME - (endFrame - startFrame); + if (delay < 0) { + delay = 0; + } else if (delay > MILLESECONDS_PER_FRAME) { + delay = MILLESECONDS_PER_FRAME; + } + SDL_Delay(delay); + } + + /* delete textures */ + SDL_DestroyTexture(shipID); + SDL_DestroyTexture(spaceID); + + /* shutdown SDL */ + SDL_Quit(); + + return 0; + +} \ No newline at end of file