OpenGl颜色数组问题

Question

OpenGl是怎么通过顶点数组来画图的，就像是画一个正方体，颜色数组有八个元素，是对应八个定顶点吗？

vertex3 pt1[8] = { {0,0,0}, {0,1,0}, {1, 0, 0},{1, 1, 0},{0, 0, 1},{0, 1, 1},{1, 0, 1},{1, 1, 1} };
color3 col1[8] = { {1,0,0},{1,0,0},{0,0,1},{0,0,1},{1,0,0},{1,0,0},{0,0,1},{0,0,1} };

glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glVertexPointer(3, GL_INT,0,pt1);
glColorPointer(3, GL_FLOAT, 0,col1);

GLuint vertIndex[] = { 6, 2, 3, 7 ,5, 1, 0, 4 ,7, 3, 1, 5 ,4, 0, 2, 6,2, 0, 1, 3 ,7, 5, 4, 6 };
glDrawElements(GL_QUADS, 24, GL_UNSIGNED_INT, vertIndex);

Answer 1

不知道你这个问题是否已经解决, 如果还没有解决的话:

• 这个问题的回答你可以参考下: https://ask.csdn.net/questions/648847
• 除此之外, 这篇博客: OpenGL基础5：第一个正方形中的 四、测试 部分也许能够解决你的问题, 你可以仔细阅读以下内容或者直接跳转源博客中阅读:
  

  看可不可以在不参考任何文章和代码的情况下，仅通过修改之前生成的三角形的代码，生成如下图形：

  

  参考代码：

  #pragma comment(lib,"glew32.lib")
  #include<iostream>
  #include<opengl/glew.h>
  #define GLEW_STATIC
  #include<GLFW/glfw3.h>
  #include<opengl/freeglut.h>
  
  void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode);
  const GLuint WIDTH = 800, HEIGHT = 600;
  
  // Shaders
  const GLchar* VShader =
  "#version 330 core\n"
  "layout (location = 0) in vec3 position;\n"
  "void main()\n"
  "{\n"
      "gl_Position = vec4(position.x, position.y, position.z, 1.0);\n"
  "}\0";
  
  const GLchar* FShaderY =
  "#version 330 core\n"
  "out vec4 color;\n"
  "void main()\n"
  "{\n"
      "color = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
  "}\n\0";
  
  const GLchar* FShaderB =
  "#version 330 core\n"
  "out vec4 color;\n"
  "void main()\n"
  "{\n"
      "color = vec4(0.1f, 0.1f, 1.0f, 1.0f);\n"
  "}\n\0";
  
  int main()
  {
      glfwInit();
      glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
      glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
      glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
      glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
  
      GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "LearnOpenGL", nullptr, nullptr);
      glfwMakeContextCurrent(window);
      glfwSetKeyCallback(window, key_callback);
      glewExperimental = GL_TRUE;
      glewInit();
  
      int width, height;
      glfwGetFramebufferSize(window, &width, &height);
      glViewport(0, 0, width, height);
  
      GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
      glShaderSource(vertexShader, 1, &VShader, NULL);
      glCompileShader(vertexShader);
      GLuint fShaderY = glCreateShader(GL_FRAGMENT_SHADER);
      glShaderSource(fShaderY, 1, &FShaderY, NULL);
      glCompileShader(fShaderY);
      GLuint fShaderB = glCreateShader(GL_FRAGMENT_SHADER);
      glShaderSource(fShaderB, 1, &FShaderB, NULL);
      glCompileShader(fShaderB);
     
      GLuint shaderYellow = glCreateProgram();
      GLuint shaderBlue = glCreateProgram();
      glAttachShader(shaderYellow, vertexShader);
      glAttachShader(shaderYellow, fShaderY);
      glLinkProgram(shaderYellow);
      glAttachShader(shaderBlue, vertexShader);
      glAttachShader(shaderBlue, fShaderB);
      glLinkProgram(shaderBlue);
  
      glDeleteShader(vertexShader);
      glDeleteShader(fShaderY);
      glDeleteShader(fShaderB);
  
      GLfloat trangleY[] =
      {
          -0.5f, -0.5f, 0.0f,
          -0.5f, 0.5f, 0.0f,
          0.0f, 0.0f, 0.0f
      };
      GLfloat trangleB[] =
      {
          0.5f, -0.5f, 0.0f,
          0.5f, 0.5f, 0.0f,
          0.0f, 0.0f, 0.0f
      };
      GLuint VBO[2], VAO[2];
      glGenVertexArrays(2, VAO);
      glGenBuffers(2, VBO);
      
      glBindVertexArray(VAO[0]);
      glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
      glBufferData(GL_ARRAY_BUFFER, sizeof(trangleY), trangleY, GL_STATIC_DRAW);
      glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
      glEnableVertexAttribArray(0);
  
      glBindVertexArray(VAO[1]);
      glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
      glBufferData(GL_ARRAY_BUFFER, sizeof(trangleB), trangleB, GL_STATIC_DRAW);
      glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
      glEnableVertexAttribArray(0);
  
      glBindBuffer(GL_ARRAY_BUFFER, 0);
      glBindVertexArray(0);
  
      while (!glfwWindowShouldClose(window))
      {
          glfwPollEvents();
          glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
          glClear(GL_COLOR_BUFFER_BIT);
  
          glUseProgram(shaderYellow);
          glBindVertexArray(VAO[0]);
          glDrawArrays(GL_TRIANGLES, 0, 3);
          glUseProgram(shaderBlue);
          glBindVertexArray(VAO[1]);
          glDrawArrays(GL_TRIANGLES, 0, 3);
  
          glBindVertexArray(0);
          glfwSwapBuffers(window);
      }
      glDeleteVertexArrays(2, VAO);
      glDeleteBuffers(2, VBO);
      glfwTerminate();
      return 0;
  }
  
  void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode)
  {
      if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
          glfwSetWindowShouldClose(window, GL_TRUE);
  }

  参考文献：

  https://learnopengl.com/#!Getting-started/OpenGL
• 您还可以看一下 杨振老师的OpenGL萌谷手册视频教程课程中的 原理？课时数？课时长度？小节, 巩固相关知识点
  

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