polygon

src/graphics.cpp

@@ -22,6 +22,9 @@ ShaderProgram::Base ShaderProgram::baseFromName(string name) {
   }
   if (lname == "triangle") {
     return Triangle;
+  }
+  if (lname == "polygons") {
+    return Polygons;
   } else {
     BOOST_LOG_TRIVIAL(fatal) << "unknown base program \"" << name << "\"";
     exit(EXIT_USAGE);
@@ -40,6 +43,8 @@ string ShaderProgram::baseName() {
     return "Empty";
   case ShaderProgram::Base::Triangle:
     return "Triangle";
+  case ShaderProgram::Base::Polygons:
+    return "Polygons";
   default:
     // this should never occur, as the switch case should cover all variants.
     throw std::runtime_error("Undefined base Program");
@@ -181,6 +186,89 @@ int ShaderProgram::run(GLFWwindow *window) {
     glDeleteBuffers(1, &VBOTriangle);
     glDeleteProgram(this->program);
 
+    // glfw: terminate, clearing all previously allocated GLFW resources.
+    // ------------------------------------------------------------------
+    glfwTerminate();
+    return 0;
+  } else if (this->base == Polygons) {
+    // set up vertex data (and buffer(s)) and configure vertex attributes
+    // ------------------------------------------------------------------
+    float vertices[] = {
+        0.5f,  0.8f,  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[] = {
+        // note that we start from 0!
+        0, 1, 3, // first triangle
+        1, 2, 3  // second triangle
+    };
+
+    unsigned int VBOTriangle, VAOTriangle, EBOindicies;
+    glGenBuffers(1, &EBOindicies);
+    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(vertices), vertices, GL_STATIC_DRAW);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBOindicies);
+    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,
+                 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);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBOindicies);
+
+    // 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);
+
+      // 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); */
+      glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
+      // 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();

src/graphics.hpp

@@ -7,7 +7,7 @@
 
 class ShaderProgram {
 public:
-  enum Base { Empty, Triangle };
+  enum Base { Empty, Triangle, Polygons };
   std::string baseName();
   static Base baseFromName(std::string name);
   ShaderProgram(Base base, std::string vertexSource, std::string fragSource);