hello square

src/gfx.c

@@ -1,6 +1,17 @@
 #include "gfx.h"
 
-SDL_Window* createWindow()
+const char* vertShaderPath = "res/shader/shader.vert";
+const char* fragShaderPath = "res/shader/shader.frag";
+
+SDL_Window* sdlWindow;
+SDL_GLContext* sdlContext;
+
+SDL_Window* getWindow() { return sdlWindow; }
+SDL_GLContext* getContext() { return sdlContext; }
+
+GLuint compileShader(const char* path, GLenum type);
+
+void gfxInit()
 {
     // load sdl modules
     if (SDL_Init(SDL_INIT_VIDEO) != 0)
@@ -14,7 +25,7 @@ SDL_Window* createWindow()
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
     SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
 
-    SDL_Window* window = SDL_CreateWindow(
+    sdlWindow = SDL_CreateWindow(
             "oglc",
             SDL_WINDOWPOS_UNDEFINED,
             SDL_WINDOWPOS_UNDEFINED,
@@ -22,21 +33,26 @@ SDL_Window* createWindow()
             600,
             SDL_WINDOW_OPENGL);
 
-    return window;
-}
-
-struct GraphicsContext createContext()
-{
-    SDL_Window* window = createWindow();
-
-    SDL_GLContext context = SDL_GL_CreateContext(window);
+    sdlContext = SDL_GL_CreateContext(sdlWindow);
 
     glewExperimental = GL_TRUE;
     glewInit();
+}
 
-    struct GraphicsContext ctx = {window, context};
+unsigned int compileShaderProgram()
+{
+    GLuint vs = compileShader(vertShaderPath, GL_VERTEX_SHADER);
+    GLuint fs = compileShader(fragShaderPath, GL_FRAGMENT_SHADER);
 
-    return ctx;
+    unsigned int shaderProgram = glCreateProgram();
+    glAttachShader(shaderProgram, vs);
+    glAttachShader(shaderProgram, fs);
+    glLinkProgram(shaderProgram);
+
+    glDeleteShader(vs);
+    glDeleteShader(fs);
+
+    return shaderProgram;
 }
 
 GLuint compileShader(const char* path, GLenum type)
@@ -74,7 +90,5 @@ GLuint compileShader(const char* path, GLenum type)
         exit(1);
     }
 
-    printf(":: . compiled shader %s! :D\n", path);
-
     return shader;
 }

src/gfx.h

@@ -8,13 +8,10 @@
 
 #include "io.h"
 
-struct GraphicsContext
-{
-    SDL_Window*     window;
-    SDL_GLContext*  context;
-};
-
-SDL_Window* createWindow();
-struct GraphicsContext createContext();
+void gfxInit();
+SDL_Window* getWindow();
+SDL_GLContext* getContext();
 GLuint compileShader(const char* path, GLenum type);
 
+unsigned int compileShaderProgram();
+

src/main.c

@@ -2,48 +2,39 @@
 
 #include "gfx.h"
 
-// data !
-const char* vertShaderPath = "res/shader/shader.vert";
-const char* fragShaderPath = "res/shader/shader.frag";
-
 float vertices[] = {
-    -0.5f, -0.5f, 0.0f,
-     0.5f, -0.5f, 0.0f,
-     0.0f,  0.5f, 0.0f
+     0.5f,  0.5f,  0.0f, // top right
+     0.5f, -0.5f,  0.0f, // bottom right
+    -0.5f, -0.5f,  0.0f, // bottom left
+    -0.5f,  0.5f,  0.0f  // top left
+};
+
+unsigned int indices[] = {
+    0, 1, 3,
+    1, 2, 3
 };
 
 // forward declarations
 int checkQuit();
 
-
 int main()
 {
-    // initialise opengl graphics context
-    const struct GraphicsContext ctx = createContext();
+    gfxInit();
+    SDL_Window* window = getWindow();
 
-    // compile shaders
-    printf(":: compiling shaders\n");
-    GLuint vertShader = compileShader(vertShaderPath, GL_VERTEX_SHADER);
-    GLuint fragShader = compileShader(fragShaderPath, GL_FRAGMENT_SHADER);
-
-    printf(":: linking shader program\n");
-    unsigned int shaderProgram = glCreateProgram();
-    glAttachShader(shaderProgram, vertShader);
-    glAttachShader(shaderProgram, fragShader);
-    glLinkProgram(shaderProgram);
-
-    glDeleteShader(vertShader);
-    glDeleteShader(fragShader);
+    unsigned int shaderProgram = compileShaderProgram();
 
     // TODO: check program linking success
 
-    // set up vertex array object
+    // vertex array object
     unsigned int VAO;
     glGenVertexArrays(1, &VAO);
-
-    // set up vertex buffer object
+    // vertex buffer object
     unsigned int VBO;                                                   
     glGenBuffers(1, &VBO);
+    // element buffer object
+    unsigned int EBO;
+    glGenBuffers(1, &EBO);
 
     glBindVertexArray(VAO);
 
@@ -51,18 +42,22 @@ int main()
     glBindBuffer(GL_ARRAY_BUFFER, VBO);                                         // bind it to the GL_ARRAY_BUFFER target
     glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);  // copy user-defined data into currently bound buffer
 
+    // copy indices into a buffer for opengl
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
+    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
+
     // set vertex attributes
     glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3*sizeof(float), (void*)0); // TODO: wtf
     glEnableVertexAttribArray(0);
 
-    // wait for exit
+    // render loop
     while (!checkQuit())
     {
         glUseProgram(shaderProgram);
-        glBindVertexArray(VAO);
-        glDrawArrays(GL_TRIANGLES, 0, 3);
 
-        SDL_GL_SwapWindow(ctx.window);
+        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
+
+        SDL_GL_SwapWindow(window);
     }
 
     return 0;

todo.md

@@ -1,3 +1,4 @@
 * [x] basic opengl initialisation
 * [ ] render a texture to a full-screen quad
 * [ ] output image to a file
+* [ ] render image with compute shader