examples: Added renderer/10-geometry

examples/CMakeLists.txt

@@ -129,6 +129,7 @@ add_sdl_example_executable(renderer-textures SOURCES renderer/06-textures/textur
 add_sdl_example_executable(renderer-streaming-textures SOURCES renderer/07-streaming-textures/streaming-textures.c)
 add_sdl_example_executable(renderer-rotating-textures SOURCES renderer/08-rotating-textures/rotating-textures.c DATAFILES ${CMAKE_CURRENT_SOURCE_DIR}/../test/sample.bmp)
 add_sdl_example_executable(renderer-scaling-textures SOURCES renderer/09-scaling-textures/scaling-textures.c DATAFILES ${CMAKE_CURRENT_SOURCE_DIR}/../test/sample.bmp)
+add_sdl_example_executable(renderer-geometry SOURCES renderer/10-geometry/geometry.c DATAFILES ${CMAKE_CURRENT_SOURCE_DIR}/../test/sample.bmp)
 add_sdl_example_executable(audio-simple-playback SOURCES audio/01-simple-playback/simple-playback.c)
 add_sdl_example_executable(audio-simple-playback-callback SOURCES audio/02-simple-playback-callback/simple-playback-callback.c)
 add_sdl_example_executable(audio-load-wav SOURCES audio/03-load-wav/load-wav.c DATAFILES ${CMAKE_CURRENT_SOURCE_DIR}/../test/sample.wav)

examples/renderer/10-geometry/README.txt

@@ -0,0 +1,3 @@
+This example creates an SDL window and renderer, loads a texture from a .bmp
+file, and then draws geometry (arbitrary polygons) using it.
+

examples/renderer/10-geometry/geometry.c

@@ -0,0 +1,172 @@
+/*
+ * This example creates an SDL window and renderer, and then draws some
+ * geometry (arbitrary polygons) to it 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;
+
+    if (!SDL_Init(SDL_INIT_VIDEO)) {
+        SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't initialize SDL!", SDL_GetError(), NULL);
+        return SDL_APP_FAILURE;
+    }
+
+    if (!SDL_CreateWindowAndRenderer("examples/renderer/geometry", WINDOW_WIDTH, WINDOW_HEIGHT, 0, &window, &renderer)) {
+        SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't create window/renderer!", SDL_GetError(), NULL);
+        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_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't load bitmap!", SDL_GetError(), NULL);
+        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_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't create static texture!", SDL_GetError(), NULL);
+        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 Uint64 now = SDL_GetTicks();
+
+    /* we'll have the triangle grow and shrink over a few seconds. */
+    const float direction = ((now % 2000) >= 1000) ? 1.0f : -1.0f;
+    const float scale = ((float) (((int) (now % 1000)) - 500) / 500.0f) * direction;
+    const float size = 200.0f + (200.0f * scale);
+
+    SDL_Vertex vertices[4];
+
+    /* as you can see from this, rendering draws over whatever was drawn before it. */
+    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);  /* black, full alpha */
+    SDL_RenderClear(renderer);  /* start with a blank canvas. */
+
+    /* Draw a single triangle with a different color at each vertex. Center this one and make it grow and shrink. */
+    /* You always draw triangles with this, but you can string triangles together to form polygons. */
+    SDL_zeroa(vertices);
+    vertices[0].position.x = ((float) WINDOW_WIDTH) / 2.0f;
+    vertices[0].position.y = (((float) WINDOW_HEIGHT) - size) / 2.0f;
+    vertices[0].color.r = 1.0f;
+    vertices[0].color.a = 1.0f;
+    vertices[1].position.x = (((float) WINDOW_WIDTH) + size) / 2.0f;
+    vertices[1].position.y = (((float) WINDOW_HEIGHT) + size) / 2.0f;
+    vertices[1].color.g = 1.0f;
+    vertices[1].color.a = 1.0f;
+    vertices[2].position.x = (((float) WINDOW_WIDTH) - size) / 2.0f;
+    vertices[2].position.y = (((float) WINDOW_HEIGHT) + size) / 2.0f;
+    vertices[2].color.b = 1.0f;
+    vertices[2].color.a = 1.0f;
+
+#if 0
+typedef struct SDL_Vertex
+{
+    SDL_FPoint position;        /**< Vertex position, in SDL_Renderer coordinates  */
+    SDL_FColor color;           /**< Vertex color */
+    SDL_FPoint tex_coord;       /**< Normalized texture coordinates, if needed */
+} SDL_Vertex;
+#endif
+
+    SDL_RenderGeometry(renderer, NULL, vertices, 3, NULL, 0);
+
+    /* you can also map a texture to the geometry! Texture coordinates go from 0.0f to 1.0f. That will be the location
+       in the texture bound to this vertex. */
+    SDL_zeroa(vertices);
+    vertices[0].position.x = 10.0f;
+    vertices[0].position.y = 10.0f;
+    vertices[0].color.r = vertices[0].color.g = vertices[0].color.b = vertices[0].color.a = 1.0f;
+    vertices[0].tex_coord.x = 0.0f;
+    vertices[0].tex_coord.y = 0.0f;
+    vertices[1].position.x = 150.0f;
+    vertices[1].position.y = 10.0f;
+    vertices[1].color.r = vertices[1].color.g = vertices[1].color.b = vertices[1].color.a = 1.0f;
+    vertices[1].tex_coord.x = 1.0f;
+    vertices[1].tex_coord.y = 0.0f;
+    vertices[2].position.x = 10.0f;
+    vertices[2].position.y = 150.0f;
+    vertices[2].color.r = vertices[2].color.g = vertices[2].color.b = vertices[2].color.a = 1.0f;
+    vertices[2].tex_coord.x = 0.0f;
+    vertices[2].tex_coord.y = 1.0f;
+    SDL_RenderGeometry(renderer, texture, vertices, 3, NULL, 0);
+
+    /* Did that only draw half of the texture? You can do multiple triangles sharing some vertices,
+       using indices, to get the whole thing on the screen: */
+
+    /* Let's just move this over so it doesn't overlap... */
+    for (int i = 0; i < 3; i++) {
+        vertices[i].position.x += 450;
+    }
+
+    /* we need one more vertex, since the two triangles can share two of them. */
+    vertices[3].position.x = 600.0f;
+    vertices[3].position.y = 150.0f;
+    vertices[3].color.r = vertices[0].color.g = vertices[0].color.b = vertices[0].color.a = 1.0f;
+    vertices[3].tex_coord.x = 1.0f;
+    vertices[3].tex_coord.y = 1.0f;
+
+    /* And an index to tell it to reuse some of the vertices between triangles... */
+    {
+    /* 4 vertices, but 6 actual places they used. Indices need less bandwidth to transfer and can reorder vertices easily! */
+    const int indices[] = { 0, 1, 2, 1, 2, 3 };
+    SDL_RenderGeometry(renderer, texture, vertices, 4, indices, SDL_arraysize(indices));
+    }
+
+    SDL_RenderPresent(renderer);  /* put it all on the screen! */
+
+    return SDL_APP_CONTINUE;  /* carry on with the program! */
+}
+
+/* This function runs once at shutdown. */
+void SDL_AppQuit(void *appstate)
+{
+    SDL_DestroyTexture(texture);
+    /* SDL will clean up the window/renderer for us. */
+}
+