From 83eea00d66139d16e8f12733b8211721f3b61a44 Mon Sep 17 00:00:00 2001
From: expikr <[EMAIL REDACTED]>
Date: Fri, 28 Mar 2025 18:39:10 +0800
Subject: [PATCH] Create affine-textures.c
---
.../19-affine-textures/affine-textures.c | 142 ++++++++++++++++++
1 file changed, 142 insertions(+)
create mode 100644 examples/renderer/19-affine-textures/affine-textures.c
diff --git a/examples/renderer/19-affine-textures/affine-textures.c b/examples/renderer/19-affine-textures/affine-textures.c
new file mode 100644
index 0000000000000..4dead3aae01fa
--- /dev/null
+++ b/examples/renderer/19-affine-textures/affine-textures.c
@@ -0,0 +1,142 @@
+/* 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. */
+ }
+
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