opengl从画三角形到画一个立方体（五）

前面的章节中，讲到了如何画一个立方体，本节的内容是画多个立方体，并让其旋转起来，不旋转，很难看到立体的效果。
首先，如何画多个立方体，我们知道MVP矩阵的作用，然后我们只要对local的坐标进行平移，旋转操作就可以画多个立方体了。

glm::vec3 cubePosition[] = {
        glm::vec3(0.0f, 0.0f, 0.0f),
        glm::vec3(0.01f, 0.0f, 0.0f),
        glm::vec3(0.0f, 0.01f, 0.0f),
        glm::vec3(-0.01f, 0.0f, 0.0f),
    };

然后就是将矩阵作用到顶点上去，一个立方体的12个三角形（每个面两个三角形，6个面，共计12个三角形，36个顶点）的顶点数据为：

float vertices[] = {
        -0.5f, -0.5f, -0.5f, 0.0f, 0.0f,
        0.5f, -0.5f, -0.5f, 1.0f, 0.0f,
        0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
        0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
        -0.5f, 0.5f, -0.5f, 0.0f, 1.0f,
        -0.5f, -0.5f, -0.5f, 0.0f, 0.0f,

        -0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
        0.5f, -0.5f, 0.5f, 1.0f, 0.0f,
        0.5f, 0.5f, 0.5f, 1.0f, 1.0f,
        0.5f, 0.5f, 0.5f, 1.0f, 1.0f,
        -0.5f, 0.5f, 0.5f, 0.0f, 1.0f,
        -0.5f, -0.5f, 0.5f, 0.0f, 0.0f,

        -0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
        -0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
        -0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
        -0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
        -0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
        -0.5f, 0.5f, 0.5f, 1.0f, 0.0f,

        0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
        0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
        0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
        0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
        0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
        0.5f, 0.5f, 0.5f, 1.0f, 0.0f,

        -0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
        0.5f, -0.5f, -0.5f, 1.0f, 1.0f,
        0.5f, -0.5f, 0.5f, 1.0f, 0.0f,
        0.5f, -0.5f, 0.5f, 1.0f, 0.0f,
        -0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
        -0.5f, -0.5f, -0.5f, 0.0f, 1.0f,

        -0.5f, 0.5f, -0.5f, 0.0f, 1.0f,
        0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
        0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
        0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
        -0.5f, 0.5f, 0.5f, 0.0f, 0.0f,
        -0.5f, 0.5f, -0.5f, 0.0f, 1.0f
    };

然后需要在主循环中，用单位矩阵做位移操作，即：

glm::mat4 model;
model = glm::translate(model, cubePosition[i]);

这里就得到平移的矩阵。

然后就是V矩阵和P矩阵的定义：

glm::mat4 view;
glm::mat4 projection;
projection = glm::perspective(glm::radians(45.0f), (float)800 / (float)600, 0.1f, 100.0f);
view = glm::translate(view, glm::vec3(0.0f, 0.0f, -3.0f));

这个两个矩阵的定义，我们之后再做讲解，最后就是改写vertex shader的内容，让其接收程序中的数据。

const char *vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"layout (location = 1) in vec2 inTexcoord;\n"
"out vec2 outTexcoord;\n"
"uniform mat4 model;\n"
"uniform mat4 view;\n"
"uniform mat4 projection;\n"
"void main()\n"
"{\n"
"   gl_Position = projection * view * model * vec4(aPos/200.0,1.0);\n"
"   outTexcoord = vec2(inTexcoord.x, inTexcoord.y);\n"
"}\0";

下面给出整体的代码：

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

using namespace std;

const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

const char *vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"layout (location = 1) in vec2 inTexcoord;\n"
"out vec2 outTexcoord;\n"
"uniform mat4 model;\n"
"uniform mat4 view;\n"
"uniform mat4 projection;\n"
"void main()\n"
"{\n"
"   gl_Position = projection * view * model * vec4(aPos/200.0,1.0);\n"
"   outTexcoord = vec2(inTexcoord.x, inTexcoord.y);\n"
"}\0";

const char *fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"in vec2 outTexcoord;\n"
"uniform sampler2D texture1;\n"
"void main()\n"
"{\n"
"   FragColor = texture(texture1, outTexcoord);\n"
"}\n\0";


int main()
{
    //初始化和创建窗口
    glfwInit();
    GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);

    //设置
    glfwMakeContextCurrent(window);
    gladLoadGLLoader((GLADloadproc)glfwGetProcAddress);


    //三角形的三个顶点数据
    float vertices[] = {
        -0.5f, -0.5f, -0.5f, 0.0f, 0.0f,
        0.5f, -0.5f, -0.5f, 1.0f, 0.0f,
        0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
        0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
        -0.5f, 0.5f, -0.5f, 0.0f, 1.0f,
        -0.5f, -0.5f, -0.5f, 0.0f, 0.0f,

        -0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
        0.5f, -0.5f, 0.5f, 1.0f, 0.0f,
        0.5f, 0.5f, 0.5f, 1.0f, 1.0f,
        0.5f, 0.5f, 0.5f, 1.0f, 1.0f,
        -0.5f, 0.5f, 0.5f, 0.0f, 1.0f,
        -0.5f, -0.5f, 0.5f, 0.0f, 0.0f,

        -0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
        -0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
        -0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
        -0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
        -0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
        -0.5f, 0.5f, 0.5f, 1.0f, 0.0f,

        0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
        0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
        0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
        0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
        0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
        0.5f, 0.5f, 0.5f, 1.0f, 0.0f,

        -0.5f, -0.5f, -0.5f, 0.0f, 1.0f,
        0.5f, -0.5f, -0.5f, 1.0f, 1.0f,
        0.5f, -0.5f, 0.5f, 1.0f, 0.0f,
        0.5f, -0.5f, 0.5f, 1.0f, 0.0f,
        -0.5f, -0.5f, 0.5f, 0.0f, 0.0f,
        -0.5f, -0.5f, -0.5f, 0.0f, 1.0f,

        -0.5f, 0.5f, -0.5f, 0.0f, 1.0f,
        0.5f, 0.5f, -0.5f, 1.0f, 1.0f,
        0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
        0.5f, 0.5f, 0.5f, 1.0f, 0.0f,
        -0.5f, 0.5f, 0.5f, 0.0f, 0.0f,
        -0.5f, 0.5f, -0.5f, 0.0f, 1.0f
    };

    glm::vec3 cubePosition[] = {
        glm::vec3(0.0f, 0.0f, 0.0f),
        glm::vec3(0.01f, 0.0f, 0.0f),
        glm::vec3(0.0f, 0.01f, 0.0f),
        glm::vec3(-0.01f, 0.0f, 0.0f),
    };

    unsigned int VBO, VAO;
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);

    glBindVertexArray(VAO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);

    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);

    int vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);

    int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    glCompileShader(fragmentShader);

    int shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);


    unsigned int texture1;
    glGenTextures(1, &texture1);
    glBindTexture(GL_TEXTURE_2D, texture1);

    stbi_set_flip_vertically_on_load(true);
    int width, height, nrChannels;
    unsigned char *data = stbi_load("timg.jpg", &width, &height, &nrChannels, 0);
    if (data)
    {
        glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
        glGenerateMipmap(GL_TEXTURE_2D);
    }
    else
    {
        std::cout << "Failed to load texture" << std::endl;
    }
    glUseProgram(shaderProgram);
    glUniform1i(glGetUniformLocation(shaderProgram, "texture1"), 0);
    glEnable(GL_DEPTH_TEST);

    while (!glfwWindowShouldClose(window))
    {
        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
        glActiveTexture(GL_TEXTURE0);
        glBindTexture(GL_TEXTURE_2D, texture1);
        glUseProgram(shaderProgram);

        glm::mat4 view;
        glm::mat4 projection;
        projection = glm::perspective(glm::radians(45.0f), (float)800 / (float)600, 0.1f, 100.0f);
        view = glm::translate(view, glm::vec3(0.0f, 0.0f, -3.0f));

        unsigned int transformLoc1 = glGetUniformLocation(shaderProgram, "projection");
        glUniformMatrix4fv(transformLoc1, 1, GL_FALSE, glm::value_ptr(projection));

        unsigned int transformLoc2 = glGetUniformLocation(shaderProgram, "view");
        glUniformMatrix4fv(transformLoc2, 1, GL_FALSE, glm::value_ptr(view));

        glBindVertexArray(VAO);

        for (int i = 0; i < 4; ++i)
        {
            glm::mat4 model;
            model = glm::translate(model, cubePosition[i]);
            model = glm::rotate(model, 20*(float)glfwGetTime()*glm::radians(50.0f), glm::vec3(1.0f, 0.3f, 0.5f));
            unsigned int transformLoc3 = glGetUniformLocation(shaderProgram, "model");
            glUniformMatrix4fv(transformLoc3, 1, GL_FALSE, glm::value_ptr(model));
            glDrawArrays(GL_TRIANGLES, 0, 36);
        }

        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    return 0;
}

运行的结果为：

接下来，我们似乎失去了学习的方向，我们不在去写一个相机了，而是迫不及待的学习光照以及shader相关的知识，所以画一个立方体的知识，暂时告一段落，接下来学习光照知识，敬请期待。。。。