🛠️🐜 Antkeeper superbuild with dependencies included
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226 lines
6.7 KiB
226 lines
6.7 KiB
/*
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* accelerometer.c
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* written by Holmes Futrell
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* use however you want
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*/
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#include "SDL.h"
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#include <math.h>
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#include "common.h"
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#define DAMPING 0.5f; /* after bouncing off a wall, damping coefficient determines final speed */
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#define FRICTION 0.0008f /* coefficient of acceleration that opposes direction of motion */
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#define GRAVITY_CONSTANT 0.004f /* how sensitive the ship is to the accelerometer */
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/* If we aren't on an iPhone, then this definition ought to yield reasonable behavior */
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#ifndef SDL_IPHONE_MAX_GFORCE
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#define SDL_IPHONE_MAX_GFORCE 5.0f
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#endif
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static SDL_Joystick *accelerometer; /* used for controlling the ship */
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static struct
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{
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float x, y; /* position of ship */
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float vx, vy; /* velocity of ship (in pixels per millesecond) */
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SDL_Rect rect; /* (drawn) position and size of ship */
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} shipData;
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static SDL_Texture *ship = 0; /* texture for spaceship */
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static SDL_Texture *space = 0; /* texture for space (background */
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void
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render(SDL_Renderer *renderer, int w, int h, double deltaTime)
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{
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double deltaMilliseconds = deltaTime * 1000;
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float speed;
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/* get joystick (accelerometer) axis values and normalize them */
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float ax = SDL_JoystickGetAxis(accelerometer, 0);
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float ay = SDL_JoystickGetAxis(accelerometer, 1);
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/* ship screen constraints */
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Uint32 minx = 0.0f;
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Uint32 maxx = w - shipData.rect.w;
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Uint32 miny = 0.0f;
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Uint32 maxy = h - shipData.rect.h;
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#define SINT16_MAX ((float)(0x7FFF))
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/* update velocity from accelerometer
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the factor SDL_IPHONE_MAX_G_FORCE / SINT16_MAX converts between
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SDL's units reported from the joytick, and units of g-force, as reported by the accelerometer
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*/
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shipData.vx +=
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ax * SDL_IPHONE_MAX_GFORCE / SINT16_MAX * GRAVITY_CONSTANT *
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deltaMilliseconds;
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shipData.vy +=
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ay * SDL_IPHONE_MAX_GFORCE / SINT16_MAX * GRAVITY_CONSTANT *
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deltaMilliseconds;
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speed = sqrt(shipData.vx * shipData.vx + shipData.vy * shipData.vy);
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if (speed > 0) {
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/* compensate for friction */
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float dirx = shipData.vx / speed; /* normalized x velocity */
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float diry = shipData.vy / speed; /* normalized y velocity */
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/* update velocity due to friction */
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if (speed - FRICTION * deltaMilliseconds > 0) {
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/* apply friction */
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shipData.vx -= dirx * FRICTION * deltaMilliseconds;
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shipData.vy -= diry * FRICTION * deltaMilliseconds;
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} else {
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/* applying friction would MORE than stop the ship, so just stop the ship */
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shipData.vx = 0.0f;
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shipData.vy = 0.0f;
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}
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}
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/* update ship location */
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shipData.x += shipData.vx * deltaMilliseconds;
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shipData.y += shipData.vy * deltaMilliseconds;
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if (shipData.x > maxx) {
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shipData.x = maxx;
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shipData.vx = -shipData.vx * DAMPING;
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} else if (shipData.x < minx) {
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shipData.x = minx;
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shipData.vx = -shipData.vx * DAMPING;
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}
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if (shipData.y > maxy) {
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shipData.y = maxy;
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shipData.vy = -shipData.vy * DAMPING;
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} else if (shipData.y < miny) {
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shipData.y = miny;
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shipData.vy = -shipData.vy * DAMPING;
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}
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/* draw the background */
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SDL_RenderCopy(renderer, space, NULL, NULL);
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/* draw the ship */
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shipData.rect.x = shipData.x;
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shipData.rect.y = shipData.y;
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SDL_RenderCopy(renderer, ship, NULL, &shipData.rect);
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/* update screen */
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SDL_RenderPresent(renderer);
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}
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void
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initializeTextures(SDL_Renderer *renderer)
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{
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SDL_Surface *bmp_surface;
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/* load the ship */
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bmp_surface = SDL_LoadBMP("ship.bmp");
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if (bmp_surface == NULL) {
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fatalError("could not ship.bmp");
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}
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/* set blue to transparent on the ship */
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SDL_SetColorKey(bmp_surface, 1,
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SDL_MapRGB(bmp_surface->format, 0, 0, 255));
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/* create ship texture from surface */
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ship = SDL_CreateTextureFromSurface(renderer, bmp_surface);
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if (ship == 0) {
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fatalError("could not create ship texture");
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}
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SDL_SetTextureBlendMode(ship, SDL_BLENDMODE_BLEND);
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/* set the width and height of the ship from the surface dimensions */
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shipData.rect.w = bmp_surface->w;
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shipData.rect.h = bmp_surface->h;
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SDL_FreeSurface(bmp_surface);
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/* load the space background */
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bmp_surface = SDL_LoadBMP("space.bmp");
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if (bmp_surface == NULL) {
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fatalError("could not load space.bmp");
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}
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/* create space texture from surface */
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space = SDL_CreateTextureFromSurface(renderer, bmp_surface);
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if (space == 0) {
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fatalError("could not create space texture");
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}
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SDL_FreeSurface(bmp_surface);
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}
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int
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main(int argc, char *argv[])
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{
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SDL_Window *window; /* main window */
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SDL_Renderer *renderer;
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int done; /* should we clean up and exit? */
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int w, h;
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/* initialize SDL */
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if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_JOYSTICK) < 0) {
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fatalError("Could not initialize SDL");
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}
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/* create main window and renderer */
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window = SDL_CreateWindow(NULL, 0, 0, 320, 480, SDL_WINDOW_FULLSCREEN | SDL_WINDOW_ALLOW_HIGHDPI);
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renderer = SDL_CreateRenderer(window, 0, 0);
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SDL_GetWindowSize(window, &w, &h);
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SDL_RenderSetLogicalSize(renderer, w, h);
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/* print out some info about joysticks and try to open accelerometer for use */
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printf("There are %d joysticks available\n", SDL_NumJoysticks());
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printf("Default joystick (index 0) is %s\n", SDL_JoystickName(0));
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accelerometer = SDL_JoystickOpen(0);
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if (accelerometer == NULL) {
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fatalError("Could not open joystick (accelerometer)");
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}
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printf("joystick number of axis = %d\n",
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SDL_JoystickNumAxes(accelerometer));
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printf("joystick number of hats = %d\n",
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SDL_JoystickNumHats(accelerometer));
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printf("joystick number of balls = %d\n",
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SDL_JoystickNumBalls(accelerometer));
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printf("joystick number of buttons = %d\n",
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SDL_JoystickNumButtons(accelerometer));
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/* load graphics */
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initializeTextures(renderer);
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/* setup ship */
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shipData.x = (w - shipData.rect.w) / 2;
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shipData.y = (h - shipData.rect.h) / 2;
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shipData.vx = 0.0f;
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shipData.vy = 0.0f;
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done = 0;
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/* enter main loop */
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while (!done) {
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double deltaTime = updateDeltaTime();
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SDL_Event event;
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while (SDL_PollEvent(&event)) {
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if (event.type == SDL_QUIT) {
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done = 1;
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}
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}
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render(renderer, w, h, deltaTime);
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SDL_Delay(1);
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}
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/* delete textures */
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SDL_DestroyTexture(ship);
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SDL_DestroyTexture(space);
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/* shutdown SDL */
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SDL_Quit();
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return 0;
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}
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