triangle

src/graphics.cpp

@@ -106,7 +106,6 @@ ShaderProgram::ShaderProgram(Base base, string vertexSource,
   }
 
   // finalizing our setup
-  glUseProgram(this->program);
   glDeleteShader(this->vertex);
   glDeleteShader(this->frag);
 }
@@ -117,29 +116,79 @@ ShaderProgram::ShaderProgram(Base base, string vertexSource,
  */
 int ShaderProgram::run(GLFWwindow *window) {
   if (this->base == Triangle) {
+    // set up vertex data (and buffer(s)) and configure vertex attributes
+    // ------------------------------------------------------------------
     float vTriangle[] = {
-        -0.5f, -0.5f, 0.0f, // opengl
-        0.5f,  -0.5f, 0.0f, // treats 3d arrays
-        0.0f,  0.5f,  0.0f  // as large 1d arrays
+        -0.5f, -0.5f, 0.0f, // left
+        0.5f,  -0.5f, 0.0f, // right
+        0.0f,  0.5f,  0.0f  // top
     };
-    unsigned int oTriangle;
-    glGenBuffers(1, &oTriangle);
-    glBindBuffer(GL_ARRAY_BUFFER, oTriangle);
+
+    unsigned int VBOTriangle, VAOTriangle;
+    glGenVertexArrays(1, &VAOTriangle);
+    glGenBuffers(1, &VBOTriangle);
+    // bind the Vertex Array Object first, then bind and set vertex buffer(s),
+    // and then configure vertex attributes(s).
+    glBindVertexArray(VAOTriangle);
+
+    glBindBuffer(GL_ARRAY_BUFFER, VBOTriangle);
     glBufferData(GL_ARRAY_BUFFER, sizeof(vTriangle), vTriangle, GL_STATIC_DRAW);
+
+    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float),
+                          (void *)0);
+    glEnableVertexAttribArray(0);
+
+    // note that this is allowed, the call to glVertexAttribPointer registered
+    // VBO as the vertex attribute's bound vertex buffer object so afterwards we
+    // can safely unbind
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+    // You can unbind the VAO afterwards so other VAO calls won't accidentally
+    // modify this VAO, but this rarely happens. Modifying other VAOs requires a
+    // call to glBindVertexArray anyways so we generally don't unbind VAOs (nor
+    // VBOs) when it's not directly necessary.
+    glBindVertexArray(0);
+
+    // uncomment this call to draw in wireframe polygons.
+    // glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
     while (!glfwWindowShouldClose(window)) {
+      // input
+      // -----
       processInput(window);
 
-      glClearColor(0.9f, 0.3f, 0.3f, 1.0f);
+      // render
+      // ------
+      glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
       glClear(GL_COLOR_BUFFER_BIT);
 
+      // draw our first triangle
+      glUseProgram(this->program);
+      glBindVertexArray(VAOTriangle); // seeing as we only have a single VAO there's no
+                              // need to bind it every time, but we'll do so to
+                              // keep things a bit more organized
+      glDrawArrays(GL_TRIANGLES, 0, 3);
+      // glBindVertexArray(0); // no need to unbind it every time
+
+      // glfw: swap buffers and poll IO events (keys pressed/released, mouse
+      // moved etc.)
+      // -------------------------------------------------------------------------------
       glfwSwapBuffers(window);
       glfwPollEvents();
     }
+    // optional: de-allocate all resources once they've outlived their purpose:
+    // ------------------------------------------------------------------------
+    glDeleteVertexArrays(1, &VAOTriangle);
+    glDeleteBuffers(1, &VBOTriangle);
+    glDeleteProgram(this->program);
+
+    // glfw: terminate, clearing all previously allocated GLFW resources.
+    // ------------------------------------------------------------------
+    glfwTerminate();
     return 0;
   } else // Empty
   {
-
-    return 0;
+    // use the compiled shader
+    glUseProgram(this->program);
     while (!glfwWindowShouldClose(window)) {
       processInput(window);