Atlas - geometry.c
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[FILE BEGIN]
1/*
2 * This example creates an SDL window and renderer, and then draws some
3 * geometry (arbitrary polygons) to it every frame.
4 *
5 * This code is public domain. Feel free to use it for any purpose!
6 */
7
8#define SDL_MAIN_USE_CALLBACKS 1  /* use the callbacks instead of main() */
9#include <SDL3/SDL.h>
10#include <SDL3/SDL_main.h>
11
12/* We will use this renderer to draw into this window every frame. */
13static SDL_Window *window = NULL;
14static SDL_Renderer *renderer = NULL;
15static SDL_Texture *texture = NULL;
16static int texture_width = 0;
17static int texture_height = 0;
18
19#define WINDOW_WIDTH 640
20#define WINDOW_HEIGHT 480
21
22/* This function runs once at startup. */
23SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
24{
25    SDL_Surface *surface = NULL;
26    char *png_path = NULL;
27
28    SDL_SetAppMetadata("Example Renderer Geometry", "1.0", "com.example.renderer-geometry");
29
30    if (!SDL_Init(SDL_INIT_VIDEO)) {
31        SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
32        return SDL_APP_FAILURE;
33    }
34
35    if (!SDL_CreateWindowAndRenderer("examples/renderer/geometry", WINDOW_WIDTH, WINDOW_HEIGHT, SDL_WINDOW_RESIZABLE, &window, &renderer)) {
36        SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
37        return SDL_APP_FAILURE;
38    }
39    SDL_SetRenderLogicalPresentation(renderer, WINDOW_WIDTH, WINDOW_HEIGHT, SDL_LOGICAL_PRESENTATION_LETTERBOX);
40
41    /* Textures are pixel data that we upload to the video hardware for fast drawing. Lots of 2D
42       engines refer to these as "sprites." We'll do a static texture (upload once, draw many
43       times) with data from a bitmap file. */
44
45    /* SDL_Surface is pixel data the CPU can access. SDL_Texture is pixel data the GPU can access.
46       Load a .png into a surface, move it to a texture from there. */
47    SDL_asprintf(&png_path, "%ssample.png", SDL_GetBasePath());  /* allocate a string of the full file path */
48    surface = SDL_LoadPNG(png_path);
49    if (!surface) {
50        SDL_Log("Couldn't load bitmap: %s", SDL_GetError());
51        return SDL_APP_FAILURE;
52    }
53
54    SDL_free(png_path);  /* done with this, the file is loaded. */
55
56    texture_width = surface->w;
57    texture_height = surface->h;
58
59    texture = SDL_CreateTextureFromSurface(renderer, surface);
60    if (!texture) {
61        SDL_Log("Couldn't create static texture: %s", SDL_GetError());
62        return SDL_APP_FAILURE;
63    }
64
65    SDL_DestroySurface(surface);  /* done with this, the texture has a copy of the pixels now. */
66
67    return SDL_APP_CONTINUE;  /* carry on with the program! */
68}
69
70/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
71SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
72{
73    if (event->type == SDL_EVENT_QUIT) {
74        return SDL_APP_SUCCESS;  /* end the program, reporting success to the OS. */
75    }
76    return SDL_APP_CONTINUE;  /* carry on with the program! */
77}
78
79/* This function runs once per frame, and is the heart of the program. */
80SDL_AppResult SDL_AppIterate(void *appstate)
81{
82    const Uint64 now = SDL_GetTicks();
83
84    /* we'll have the triangle grow and shrink over a few seconds. */
85    const float direction = ((now % 2000) >= 1000) ? 1.0f : -1.0f;
86    const float scale = ((float) (((int) (now % 1000)) - 500) / 500.0f) * direction;
87    const float size = 200.0f + (200.0f * scale);
88
89    SDL_Vertex vertices[4];
90    int i;
91
92    /* as you can see from this, rendering draws over whatever was drawn before it. */
93    SDL_SetRenderDrawColor(renderer, 0, 0, 0, SDL_ALPHA_OPAQUE);  /* black, full alpha */
94    SDL_RenderClear(renderer);  /* start with a blank canvas. */
95
96    /* Draw a single triangle with a different color at each vertex. Center this one and make it grow and shrink. */
97    /* You always draw triangles with this, but you can string triangles together to form polygons. */
98    SDL_zeroa(vertices);
99    vertices[0].position.x = ((float) WINDOW_WIDTH) / 2.0f;
100    vertices[0].position.y = (((float) WINDOW_HEIGHT) - size) / 2.0f;
101    vertices[0].color.r = 1.0f;
102    vertices[0].color.a = 1.0f;
103    vertices[1].position.x = (((float) WINDOW_WIDTH) + size) / 2.0f;
104    vertices[1].position.y = (((float) WINDOW_HEIGHT) + size) / 2.0f;
105    vertices[1].color.g = 1.0f;
106    vertices[1].color.a = 1.0f;
107    vertices[2].position.x = (((float) WINDOW_WIDTH) - size) / 2.0f;
108    vertices[2].position.y = (((float) WINDOW_HEIGHT) + size) / 2.0f;
109    vertices[2].color.b = 1.0f;
110    vertices[2].color.a = 1.0f;
111
112    SDL_RenderGeometry(renderer, NULL, vertices, 3, NULL, 0);
113
114    /* you can also map a texture to the geometry! Texture coordinates go from 0.0f to 1.0f. That will be the location
115       in the texture bound to this vertex. */
116    SDL_zeroa(vertices);
117    vertices[0].position.x = 10.0f;
118    vertices[0].position.y = 10.0f;
119    vertices[0].color.r = vertices[0].color.g = vertices[0].color.b = vertices[0].color.a = 1.0f;
120    vertices[0].tex_coord.x = 0.0f;
121    vertices[0].tex_coord.y = 0.0f;
122    vertices[1].position.x = 150.0f;
123    vertices[1].position.y = 10.0f;
124    vertices[1].color.r = vertices[1].color.g = vertices[1].color.b = vertices[1].color.a = 1.0f;
125    vertices[1].tex_coord.x = 1.0f;
126    vertices[1].tex_coord.y = 0.0f;
127    vertices[2].position.x = 10.0f;
128    vertices[2].position.y = 150.0f;
129    vertices[2].color.r = vertices[2].color.g = vertices[2].color.b = vertices[2].color.a = 1.0f;
130    vertices[2].tex_coord.x = 0.0f;
131    vertices[2].tex_coord.y = 1.0f;
132    SDL_RenderGeometry(renderer, texture, vertices, 3, NULL, 0);
133
134    /* Did that only draw half of the texture? You can do multiple triangles sharing some vertices,
135       using indices, to get the whole thing on the screen: */
136
137    /* Let's just move this over so it doesn't overlap... */
138    for (i = 0; i < 3; i++) {
139        vertices[i].position.x += 450;
140    }
141
142    /* we need one more vertex, since the two triangles can share two of them. */
143    vertices[3].position.x = 600.0f;
144    vertices[3].position.y = 150.0f;
145    vertices[3].color.r = vertices[3].color.g = vertices[3].color.b = vertices[3].color.a = 1.0f;
146    vertices[3].tex_coord.x = 1.0f;
147    vertices[3].tex_coord.y = 1.0f;
148
149    /* And an index to tell it to reuse some of the vertices between triangles... */
150    {
151    /* 4 vertices, but 6 actual places they used. Indices need less bandwidth to transfer and can reorder vertices easily! */
152    const int indices[] = { 0, 1, 2, 1, 2, 3 };
153    SDL_RenderGeometry(renderer, texture, vertices, 4, indices, SDL_arraysize(indices));
154    }
155
156    SDL_RenderPresent(renderer);  /* put it all on the screen! */
157
158    return SDL_APP_CONTINUE;  /* carry on with the program! */
159}
160
161/* This function runs once at shutdown. */
162void SDL_AppQuit(void *appstate, SDL_AppResult result)
163{
164    SDL_DestroyTexture(texture);
165    /* SDL will clean up the window/renderer for us. */
166}
167
168
[FILE END]
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