1. 来源：《Computer Graphics Programming in OpenGL Using C++ 》by V Scott Gordon John L Clevenger
2. 内容：程序4.1 Program 4.1 Plain Red Cube，书P78页，PDF97/403
3. 相关介绍可参考 C++/OpenGL 入门(8):画一个转动的彩色立方体
4. 结果，生成多个转动的彩色立方体，如下

C++/OpenGL 入门(9):复制同一立方体进行多物体运动

5. 文件1：220203 4.13 redCube.cpp

#include <string>
#include <iostream>
#include <fstream>
#include <cmath>


#include "glm\glm.hpp"
#include "glm\gtc\type_ptr.hpp"
#include "glm\gtc\matrix_transform.hpp"
#include "Utils\4.1 Utils.h"
using namespace std;
#define numVAOs 1
#define numVBOs 2
float cameraX, cameraY, cameraZ;
float cubeLocX, cubeLocY, cubeLocZ;
GLuint renderingProgram;
GLuint vao[numVAOs];
GLuint vbo[numVBOs];

// allocate variables used in display() function, 
// so that they won’t need to be allocated during rendering
GLuint mvLoc, projLoc;
int width, height;
float aspect;
glm::mat4 pMat, vMat, mMat, mvMat;
glm::mat4 tMat, rMat;//为了动画而添加的内容

void setupVertices(void) {
	// 36 vertices, 12 triangles, makes 2x2x2 cube placed at origin
	float vertexPositions[108] = {
	 -1.0f, 1.0f, -1.0f, -1.0f, -1.0f, -1.0f, 1.0f, -1.0f, -1.0f,
	 1.0f, -1.0f, -1.0f, 1.0f, 1.0f, -1.0f, -1.0f, 1.0f, -1.0f,
	 1.0f, -1.0f, -1.0f, 1.0f, -1.0f, 1.0f, 1.0f, 1.0f, -1.0f,
	 1.0f, -1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, -1.0f,
	 1.0f, -1.0f, 1.0f, -1.0f, -1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
	 -1.0f, -1.0f, 1.0f, -1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
	 -1.0f, -1.0f, 1.0f, -1.0f, -1.0f, -1.0f, -1.0f, 1.0f, 1.0f,
	 -1.0f, -1.0f, -1.0f, -1.0f, 1.0f, -1.0f, -1.0f, 1.0f, 1.0f,
	 -1.0f, -1.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f, -1.0f, -1.0f,
	 1.0f, -1.0f, -1.0f, -1.0f, -1.0f, -1.0f, -1.0f, -1.0f, 1.0f,
	 -1.0f, 1.0f, -1.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f, 1.0f,
	 1.0f, 1.0f, 1.0f, -1.0f, 1.0f, 1.0f, -1.0f, 1.0f, -1.0f
	};
	glGenVertexArrays(1, vao);
	glBindVertexArray(vao[0]);
	glGenBuffers(numVBOs, vbo);
	glBindBuffer(GL_ARRAY_BUFFER, vbo[0]);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertexPositions), vertexPositions, GL_STATIC_DRAW);
}
void init(GLFWwindow* window) {

	//renderingProgram = createShaderProgram("add/4.1 vertShader.glsl", "add/4.1 fragShader.glsl");
	renderingProgram = createShaderProgram("add/4.12 vertShader.glsl", "add/4.12 fragShader.glsl");
	cameraX = 0.0f; cameraY = 0.0f; cameraZ = 50.0f;
	cubeLocX = 0.0f; cubeLocY = -2.0f; cubeLocZ = 0.0f; // shift down Y to reveal perspective
	setupVertices();
}

void display(GLFWwindow* window, double currentTime) {
	glClear(GL_DEPTH_BUFFER_BIT);
	glClearColor(0.0, 0.0, 0.0, 1.0);
	glClear(GL_COLOR_BUFFER_BIT); // 每一次都将背景清理（clear）为黑色
	glUseProgram(renderingProgram);
	// get the uniform variables for the MV and projection matrices
	mvLoc = glGetUniformLocation(renderingProgram, "mv_matrix");
	projLoc = glGetUniformLocation(renderingProgram, "proj_matrix");
	// build perspective matrix
	glfwGetFramebufferSize(window, &width, &height);
	aspect = (float)width / (float)height;
	pMat = glm::perspective(1.0472f, aspect, 0.1f, 1000.0f); // 1.0472 radians = 60 degrees
	// build view matrix, model matrix, and model-view matrix
	for (int i = 0; i < 24; i++)
	{
		float tf = currentTime + i;
		// ============ 以下是为了动画而添加的内容
		// use current time to compute different translations in x, y, and z
		tMat = glm::translate(glm::mat4(1.0f),
			glm::vec3(sin(0.35f*tf)*10.0f, cos(0.52f*tf)*10.0f, sin(0.7f*tf)*10.0f));
		rMat = glm::rotate(glm::mat4(1.0f), 1.75f*tf, glm::vec3(0.0f, 1.0f, 0.0f));
		rMat = glm::rotate(rMat, 1.75f*tf, glm::vec3(1.0f, 0.0f, 0.0f));
		rMat = glm::rotate(rMat, 1.75f*tf, glm::vec3(0.0f, 0.0f, 1.0f));
		// the 1.75 adjusts the rotation speed
		mMat = tMat * rMat;
		// ============ 结束

		vMat = glm::translate(glm::mat4(1.0f), glm::vec3(-cameraX, -cameraY, -cameraZ));

		mvMat = vMat * mMat;
		// copy perspective and MV matrices to corresponding uniform variables
		glUniformMatrix4fv(mvLoc, 1, GL_FALSE, glm::value_ptr(mvMat));
		glUniformMatrix4fv(projLoc, 1, GL_FALSE, glm::value_ptr(pMat));
		// associate VBO with the corresponding vertex attribute in the vertex shader
		glBindBuffer(GL_ARRAY_BUFFER, vbo[0]);
		glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
		glEnableVertexAttribArray(0);
		// adjust OpenGL settings and draw model
		glEnable(GL_DEPTH_TEST);
		glDepthFunc(GL_LEQUAL);
		glDrawArrays(GL_TRIANGLES, 0, 36);

	}
}

int main(void) { // main() is unchanged from before
	if (!glfwInit()) { exit(EXIT_FAILURE); }
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	GLFWwindow* window = glfwCreateWindow(600, 600, "Chapter 4 - program 1", NULL, NULL);
	glfwMakeContextCurrent(window);
	if (glewInit() != GLEW_OK) { exit(EXIT_FAILURE); }
	glfwSwapInterval(1);
	init(window);
	while (!glfwWindowShouldClose(window)) {
		display(window, glfwGetTime());
		glfwSwapBuffers(window);
		glfwPollEvents();
	}
	glfwDestroyWindow(window);
	glfwTerminate();
	exit(EXIT_SUCCESS);
}

6. 文件2： 4.12 vertShader.glsl
   （文件中放置在add文件夹中，所以cpp调用时有 add/4.1 vertShader.glsl, 可以根据需要更改）
   这是生成彩色的立方体

#version 430
layout (location=0) in vec3 position;
uniform mat4 mv_matrix;
uniform mat4 proj_matrix;
out vec4 varyingColor;
void main(void)
{ gl_Position = proj_matrix * mv_matrix * vec4(position,1.0);
varyingColor = vec4(position,1.0) * 0.5 + vec4(0.5, 0.5, 0.5, 0.5);
}

7. 文件3： 4.12 fragShader.glsl
   （文件中放置在add文件夹中，所以cpp调用时有 add/4.12 fragShader.glsl, 可以根据需要更改）
   这是生成彩色的立方体

#version 430
in vec4 varyingColor;
out vec4 color;
uniform mat4 mv_matrix;
uniform mat4 proj_matrix;
void main(void)
{ color = varyingColor;
}