Create affine-textures.c

examples/renderer/19-affine-textures/affine-textures.c

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+/* affine-textures.c ... */
+
+/*
+ * This example creates an SDL window and renderer, and then draws a cube
+ * using affine-transformed textures every frame.
+ *
+ * This code is public domain. Feel free to use it for any purpose!
+ */
+
+ #define SDL_MAIN_USE_CALLBACKS 1  /* use the callbacks instead of main() */
+ #include <SDL3/SDL.h>
+ #include <SDL3/SDL_main.h>
+ 
+ /* We will use this renderer to draw into this window every frame. */
+ static SDL_Window *window = NULL;
+ static SDL_Renderer *renderer = NULL;
+ static SDL_Texture *texture = NULL;
+ static int texture_width = 0;
+ static int texture_height = 0;
+ 
+ #define WINDOW_WIDTH 640
+ #define WINDOW_HEIGHT 480
+ 
+ /* This function runs once at startup. */
+ SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
+ {
+     SDL_Surface *surface = NULL;
+     char *bmp_path = NULL;
+ 
+     SDL_SetAppMetadata("Example Renderer Affine Textures", "1.0", "com.example.renderer-affine-textures");
+ 
+     if (!SDL_Init(SDL_INIT_VIDEO)) {
+         SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
+         return SDL_APP_FAILURE;
+     }
+ 
+     if (!SDL_CreateWindowAndRenderer("examples/renderer/affine-textures", WINDOW_WIDTH, WINDOW_HEIGHT, 0, &window, &renderer)) {
+         SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
+         return SDL_APP_FAILURE;
+     }
+ 
+     /* Textures are pixel data that we upload to the video hardware for fast drawing. Lots of 2D
+        engines refer to these as "sprites." We'll do a static texture (upload once, draw many
+        times) with data from a bitmap file. */
+ 
+     /* SDL_Surface is pixel data the CPU can access. SDL_Texture is pixel data the GPU can access.
+        Load a .bmp into a surface, move it to a texture from there. */
+     SDL_asprintf(&bmp_path, "%ssample.bmp", SDL_GetBasePath());  /* allocate a string of the full file path */
+     surface = SDL_LoadBMP(bmp_path);
+     if (!surface) {
+         SDL_Log("Couldn't load bitmap: %s", SDL_GetError());
+         return SDL_APP_FAILURE;
+     }
+ 
+     SDL_free(bmp_path);  /* done with this, the file is loaded. */
+ 
+     texture_width = surface->w;
+     texture_height = surface->h;
+ 
+     texture = SDL_CreateTextureFromSurface(renderer, surface);
+     if (!texture) {
+         SDL_Log("Couldn't create static texture: %s", SDL_GetError());
+         return SDL_APP_FAILURE;
+     }
+ 
+     SDL_DestroySurface(surface);  /* done with this, the texture has a copy of the pixels now. */
+ 
+     return SDL_APP_CONTINUE;  /* carry on with the program! */
+ }
+ 
+ /* This function runs when a new event (mouse input, keypresses, etc) occurs. */
+ SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
+ {
+     if (event->type == SDL_EVENT_QUIT) {
+         return SDL_APP_SUCCESS;  /* end the program, reporting success to the OS. */
+     }
+     return SDL_APP_CONTINUE;  /* carry on with the program! */
+ }
+ 
+ /* This function runs once per frame, and is the heart of the program. */
+ SDL_AppResult SDL_AppIterate(void *appstate) {
+     const float x0 = 0.5f * WINDOW_WIDTH;
+     const float y0 = 0.5f * WINDOW_HEIGHT;
+     const float px = SDL_min(WINDOW_WIDTH, WINDOW_HEIGHT) / SDL_sqrt(3.0);
+ 
+     const Uint64 now = SDL_GetTicks();
+     const float rad = (((float) ((int) (now % 4000))) / 4000.0f) * SDL_PI_F * 2;
+     const float cos = SDL_cos(rad);
+     const float sin = SDL_sin(rad);
+     const float k[3] = { 3.0f / SDL_sqrt(50.0), 4.0f / SDL_sqrt(50.0), 5.0f / SDL_sqrt(50.0)};
+     float mat[9] = { 
+          cos      + (1.0f-cos)*k[0]*k[0], -sin*k[2] + (1.0f-cos)*k[0]*k[1],  sin*k[1] + (1.0f-cos)*k[0]*k[2], 
+          sin*k[2] + (1.0f-cos)*k[0]*k[1],  cos      + (1.0f-cos)*k[1]*k[1], -sin*k[0] + (1.0f-cos)*k[1]*k[2], 
+         -sin*k[1] + (1.0f-cos)*k[0]*k[2],  sin*k[0] + (1.0f-cos)*k[1]*k[2],  cos      + (1.0f-cos)*k[2]*k[2],
+     };
+ 
+     float corners[16];
+     for (int i = 0; i < 8; i++) {
+         const float x = (i & 1) ? 0.5f : -0.5f;
+         const float y = (i & 2) ? 0.5f : -0.5f;
+         const float z = (i & 4) ? 0.5f : -0.5f;
+         corners[0 + 2*i] = mat[0]*x + mat[1]*y + mat[2]*z;
+         corners[1 + 2*i] = mat[3]*x + mat[4]*y + mat[5]*z;
+     }
+ 
+     SDL_SetRenderDrawColor(renderer, 0, 0, 0, SDL_ALPHA_OPAQUE);
+     SDL_RenderClear(renderer);
+ 
+     for (int i = 1; i < 7; i++) {
+         const int dir = 3 & ((i & 4) ? ~i : i);
+         const int odd = (i & 1) ^ ((i & 2) >> 1) ^ ((i & 4) >> 2);
+         if (0 < (odd ? 1.0f : -1.0f) * mat[5 + dir]) continue;
+         int origin_index = (1 << ((dir - 1) % 3));
+         int right_index = (1 << ((dir + odd) % 3)) | origin_index;
+         int down_index = (1 << ((dir + (odd^1)) % 3)) | origin_index;
+         if (!odd) {
+             origin_index ^= 7;
+             right_index ^= 7;
+             down_index ^= 7;
+         }
+         SDL_FPoint origin, right, down;
+         origin.x = x0 + px*corners[0 + 2*origin_index];
+         origin.y = y0 + px*corners[1 + 2*origin_index];
+         right.x  = x0 + px*corners[0 + 2*right_index];
+         right.y  = y0 + px*corners[1 + 2*right_index];
+         down.x   = x0 + px*corners[0 + 2*down_index];
+         down.y   = y0 + px*corners[1 + 2*down_index];
+         SDL_RenderTextureAffine(renderer, texture, NULL, &origin, &right, &down);
+     }
+ 
+     SDL_RenderPresent(renderer);
+ 
+     return SDL_APP_CONTINUE;
+ }
+ 
+ /* This function runs once at shutdown. */
+ void SDL_AppQuit(void *appstate, SDL_AppResult result)
+ {
+     SDL_DestroyTexture(texture);
+     /* SDL will clean up the window/renderer for us. */
+ }
+