LearnOpenGL练习

你好，三角形

添加更多顶点到数据中，使用glDrawArrays，尝试绘制两个彼此相连的三角形

#include "pch.h"


#include <iostream>

#include <GL/glew.h>
#include <GLFW/glfw3.h>


// Function prototypes
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode);

// Window dimensions
const GLuint WIDTH = 800, HEIGHT = 600;

// Shaders
const GLchar* vertexShaderSource = "#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* fragmentShaderSource = "#version 330 core\n"
"out vec4 color;\n"
"void main()\n"
"{\n"
"color = vec4(1.0f, 0.7f, 0.3f, 0.8f);\n"
"}\n\0";

// The MAIN function, from here we start the application and run the game loop
int main()
{
	std::cout << "Starting GLFW context, OpenGL 3.3" << std::endl;
	// Init GLFW
	glfwInit();
	// Set all the required options for GLFW
	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);

	// Create a GLFWwindow object that we can use for GLFW's functions
	GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "LearnOpenGL", nullptr, nullptr);
	glfwMakeContextCurrent(window);

	// Set the required callback functions
	glfwSetKeyCallback(window, key_callback);

	// Set this to true so GLEW knows to use a modern approach to retrieving function pointers and extensions
	glewExperimental = GL_TRUE;
	// Initialize GLEW to setup the OpenGL Function pointers
	glewInit();

	// Define the viewport dimensions
	int width, height;
	glfwGetFramebufferSize(window, &width, &height);
	glViewport(0, 0, width, height);


	// Build and compile our shader program
	// Vertex shader
	GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);
	// Check for compile time errors
	GLint success;
	GLchar infoLog[512];
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
	}
	// Fragment shader
	GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
	glCompileShader(fragmentShader);
	// Check for compile time errors
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
	}
	// Link shaders
	GLuint shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);
	// Check for linking errors
	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
	}
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);


	// Set up vertex data (and buffer(s)) and attribute pointers
	//GLfloat vertices[] = {
	//  // First triangle
	//   0.5f,  0.5f,  // Top Right
	//   0.5f, -0.5f,  // Bottom Right
	//  -0.5f,  0.5f,  // Top Left 
	//  // Second triangle
	//   0.5f, -0.5f,  // Bottom Right
	//  -0.5f, -0.5f,  // Bottom Left
	//  -0.5f,  0.5f   // Top Left
	//}; 
	GLfloat vertices[] = {
		0.5f,  0.5f, 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 
	};
	GLuint indices[] = {  // Note that we start from 0!
		0, 1, 3,  // First Triangle
		1, 2, 3   // Second Triangle
	};
	GLuint VBO, VAO, EBO;
	glGenVertexArrays(1, &VAO);
	glGenBuffers(1, &VBO);
	glGenBuffers(1, &EBO);
	// Bind the Vertex Array Object first, then bind and set vertex buffer(s) and attribute pointer(s).
	glBindVertexArray(VAO);

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

	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
	glEnableVertexAttribArray(0);

	glBindBuffer(GL_ARRAY_BUFFER, 0); // Note that this is allowed, the call to glVertexAttribPointer registered VBO as the currently bound vertex buffer object so afterwards we can safely unbind

	glBindVertexArray(0); // Unbind VAO (it's always a good thing to unbind any buffer/array to prevent strange bugs), remember: do NOT unbind the EBO, keep it bound to this VAO


	// Uncommenting this call will result in wireframe polygons.
	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

	// Game loop
	while (!glfwWindowShouldClose(window))
	{
		// Check if any events have been activiated (key pressed, mouse moved etc.) and call corresponding response functions
		glfwPollEvents();

		// Render
		// Clear the colorbuffer
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		// Draw our first triangle
		glUseProgram(shaderProgram);
		glBindVertexArray(VAO);
		//glDrawArrays(GL_TRIANGLES, 0, 6);
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
		glBindVertexArray(0);

		// Swap the screen buffers
		glfwSwapBuffers(window);
	}
	// Properly de-allocate all resources once they've outlived their purpose
	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	glDeleteBuffers(1, &EBO);
	// Terminate GLFW, clearing any resources allocated by GLFW.
	glfwTerminate();
	return 0;
}

// Is called whenever a key is pressed/released via GLFW
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);
}

创建相同的两个三角形，但对它们的数据使用不同的VAO和VBO

#include "pch.h"


#include <iostream>

#include <GL/glew.h>
#include <GLFW/glfw3.h>


// Function prototypes
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode);

// Window dimensions
const GLuint WIDTH = 800, HEIGHT = 600;

// Shaders
const GLchar* vertexShaderSource = "#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* fragmentShaderSource = "#version 330 core\n"
"out vec4 color;\n"
"void main()\n"
"{\n"
"color = vec4(1.0f, 0.7f, 0.3f, 0.8f);\n"
"}\n\0";

// The MAIN function, from here we start the application and run the game loop
int main()
{
	std::cout << "Starting GLFW context, OpenGL 3.3" << std::endl;
	// Init GLFW
	glfwInit();
	// Set all the required options for GLFW
	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);

	// Create a GLFWwindow object that we can use for GLFW's functions
	GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "LearnOpenGL", nullptr, nullptr);
	glfwMakeContextCurrent(window);

	// Set the required callback functions
	glfwSetKeyCallback(window, key_callback);

	// Set this to true so GLEW knows to use a modern approach to retrieving function pointers and extensions
	glewExperimental = GL_TRUE;
	// Initialize GLEW to setup the OpenGL Function pointers
	glewInit();

	// Define the viewport dimensions
	int width, height;
	glfwGetFramebufferSize(window, &width, &height);
	glViewport(0, 0, width, height);


	// Build and compile our shader program
	// Vertex shader
	GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);
	// Check for compile time errors
	GLint success;
	GLchar infoLog[512];
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
	}
	// Fragment shader
	GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
	glCompileShader(fragmentShader);
	// Check for compile time errors
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
	}
	// Link shaders
	GLuint shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);
	// Check for linking errors
	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
	}
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);


	// Set up vertex data (and buffer(s)) and attribute pointers
	
	GLfloat rect0[] = {
		0.5f,  0.5f, 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 
	};
	GLfloat rect1[] = {
		1.0f,  0.0f, 0.0f,  // Top Right
		1.0f, -1.0f, 0.0f,  // Bottom Right
		0.5f, -1.0f, 0.0f,  // Bottom Left
		0.5f,  0.0f, 0.0f   // Top Left 
	};

	GLuint indices0[] = {  // Note that we start from 0!
		0, 1, 3,  // First Triangle
		1, 2, 3   // Second Triangle
	};

	GLuint indices1[] = {  // Note that we start from 0!
		0, 1, 3,  // First Triangle
		1, 2, 3   // Second Triangle
	};

	GLuint VBO[2], VAO[2], EBO[2];
	glGenVertexArrays(2, VAO);
	glGenBuffers(2, VBO);
	glGenBuffers(2, EBO);
	// Bind the Vertex Array Object first, then bind and set vertex buffer(s) and attribute pointer(s).
	glBindVertexArray(VAO[0]);

	glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
	glBufferData(GL_ARRAY_BUFFER, sizeof(rect0), rect0, GL_STATIC_DRAW);

	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[0]);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices0), indices0, GL_STATIC_DRAW);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);
	glEnableVertexAttribArray(0);

	glBindBuffer(GL_ARRAY_BUFFER, 0); // Note that this is allowed, the call to glVertexAttribPointer registered VBO as the currently bound vertex buffer object so afterwards we can safely unbind

	glBindVertexArray(0); // Unbind VAO (it's always a good thing to unbind any buffer/array to prevent strange bugs), remember: do NOT unbind the EBO, keep it bound to this VAO
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

	// Bind the Vertex Array Object first, then bind and set vertex buffer(s) and attribute pointer(s).
	glBindVertexArray(VAO[1]);

	glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
	glBufferData(GL_ARRAY_BUFFER, sizeof(rect1), rect1, GL_STATIC_DRAW);

	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[1]);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices1), indices1, GL_STATIC_DRAW);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);
	glEnableVertexAttribArray(0);

	glBindBuffer(GL_ARRAY_BUFFER, 0); // Note that this is allowed, the call to glVertexAttribPointer registered VBO as the currently bound vertex buffer object so afterwards we can safely unbind

	glBindVertexArray(0); // Unbind VAO (it's always a good thing to unbind any buffer/array to prevent strange bugs), remember: do NOT unbind the EBO, keep it bound to this VAO
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);


	// Uncommenting this call will result in wireframe polygons.
	glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

	// Game loop
	while (!glfwWindowShouldClose(window))
	{
		// Check if any events have been activiated (key pressed, mouse moved etc.) and call corresponding response functions
		glfwPollEvents();

		// Render
		// Clear the colorbuffer
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		// Draw our first triangle
		glUseProgram(shaderProgram);
		glBindVertexArray(VAO[0]);
		//glDrawArrays(GL_TRIANGLES, 0, 6);
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
		glBindVertexArray(VAO[1]);
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
		glBindVertexArray(0);

		// Swap the screen buffers
		glfwSwapBuffers(window);
	}
	// Properly de-allocate all resources once they've outlived their purpose
	glDeleteVertexArrays(2, VAO);
	glDeleteBuffers(2, VBO);
	glDeleteBuffers(2, EBO);
	// Terminate GLFW, clearing any resources allocated by GLFW.
	glfwTerminate();
	return 0;
}

// Is called whenever a key is pressed/released via GLFW
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);
}

创建两个着色器程序，第二个程序使用与第一个不同的片段着色器，输出黄色；再次绘制这两个三角形，其中一个输出为黄色

#include "pch.h"


#include <iostream>

#include <GL/glew.h>
#include <GLFW/glfw3.h>


// Function prototypes
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode);

// Window dimensions
const GLuint WIDTH = 800, HEIGHT = 600;

// Shaders
const GLchar* vertexShaderSource = "#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* fragmentShaderSourceY = "#version 330 core\n"
"out vec4 color;\n"
"void main()\n"
"{\n"
"color = vec4(1.0f, 0.7f, 0.3f, 0.8f);\n"
"}\n\0";

const GLchar* fragmentShaderSourceG = "#version 330 core\n"
"out vec4 color;\n"
"void main()\n"
"{\n"
"color = vec4(0.2f, 0.8f, 0.6f, 0.8f);\n"
"}\n\0";

// The MAIN function, from here we start the application and run the game loop
int main()
{
	std::cout << "Starting GLFW context, OpenGL 3.3" << std::endl;
	// Init GLFW
	glfwInit();
	// Set all the required options for GLFW
	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);

	// Create a GLFWwindow object that we can use for GLFW's functions
	GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "LearnOpenGL", nullptr, nullptr);
	glfwMakeContextCurrent(window);

	// Set the required callback functions
	glfwSetKeyCallback(window, key_callback);

	// Set this to true so GLEW knows to use a modern approach to retrieving function pointers and extensions
	glewExperimental = GL_TRUE;
	// Initialize GLEW to setup the OpenGL Function pointers
	glewInit();

	// Define the viewport dimensions
	int width, height;
	glfwGetFramebufferSize(window, &width, &height);
	glViewport(0, 0, width, height);


	// Build and compile our shader program
	// Vertex shader
	GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);
	// Check for compile time errors
	GLint success;
	GLchar infoLog[512];
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
	}
	// Fragment shader Y
	GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSourceY, NULL);
	glCompileShader(fragmentShader);
	// Check for compile time errors
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
	}
	

	// Link shaders Y
	GLuint shaderProgramY = glCreateProgram();
	glAttachShader(shaderProgramY, vertexShader);
	glAttachShader(shaderProgramY, fragmentShader);
	glLinkProgram(shaderProgramY);
	// Check for linking errors
	glGetProgramiv(shaderProgramY, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgramY, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
	}

	// Fragment shader G
	fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSourceG, NULL);
	glCompileShader(fragmentShader);
	// Check for compile time errors
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
	}

	// Link shaders G
	GLuint shaderProgramG = glCreateProgram();
	glAttachShader(shaderProgramG, vertexShader);
	glAttachShader(shaderProgramG, fragmentShader);
	glLinkProgram(shaderProgramG);
	// Check for linking errors
	glGetProgramiv(shaderProgramG, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgramG, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
	}

	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);


	// Set up vertex data (and buffer(s)) and attribute pointers
	GLfloat rect0[] = {
		0.5f,  0.5f, 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 
	};
	GLfloat rect1[] = {
		1.0f,  0.0f, 0.0f,  // Top Right
		1.0f, -1.0f, 0.0f,  // Bottom Right
		0.5f, -1.0f, 0.0f,  // Bottom Left
		0.5f,  0.0f, 0.0f   // Top Left 
	};

	GLuint indices0[] = {  // Note that we start from 0!
		0, 1, 3,  // First Triangle
		1, 2, 3   // Second Triangle
	};

	GLuint indices1[] = {  // Note that we start from 0!
		0, 1, 3,  // First Triangle
		1, 2, 3   // Second Triangle
	};

	GLuint VBO[2], VAO[2], EBO[2];
	glGenVertexArrays(2, VAO);
	glGenBuffers(2, VBO);
	glGenBuffers(2, EBO);
	// Bind the Vertex Array Object first, then bind and set vertex buffer(s) and attribute pointer(s).
	glBindVertexArray(VAO[0]);

	glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
	glBufferData(GL_ARRAY_BUFFER, sizeof(rect0), rect0, GL_STATIC_DRAW);

	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[0]);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices0), indices0, GL_STATIC_DRAW);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);
	glEnableVertexAttribArray(0);

	glBindBuffer(GL_ARRAY_BUFFER, 0); // Note that this is allowed, the call to glVertexAttribPointer registered VBO as the currently bound vertex buffer object so afterwards we can safely unbind

	glBindVertexArray(0); // Unbind VAO (it's always a good thing to unbind any buffer/array to prevent strange bugs), remember: do NOT unbind the EBO, keep it bound to this VAO
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);

	// Bind the Vertex Array Object first, then bind and set vertex buffer(s) and attribute pointer(s).
	glBindVertexArray(VAO[1]);

	glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
	glBufferData(GL_ARRAY_BUFFER, sizeof(rect1), rect1, GL_STATIC_DRAW);

	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO[1]);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices1), indices1, GL_STATIC_DRAW);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);
	glEnableVertexAttribArray(0);

	glBindBuffer(GL_ARRAY_BUFFER, 0); // Note that this is allowed, the call to glVertexAttribPointer registered VBO as the currently bound vertex buffer object so afterwards we can safely unbind

	glBindVertexArray(0); // Unbind VAO (it's always a good thing to unbind any buffer/array to prevent strange bugs), remember: do NOT unbind the EBO, keep it bound to this VAO
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);


	// Uncommenting this call will result in wireframe polygons.
	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

	// Game loop
	while (!glfwWindowShouldClose(window))
	{
		// Check if any events have been activiated (key pressed, mouse moved etc.) and call corresponding response functions
		glfwPollEvents();

		// Render
		// Clear the colorbuffer
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		// Draw our first rect
		glUseProgram(shaderProgramY);
		glBindVertexArray(VAO[0]);
		//glDrawArrays(GL_TRIANGLES, 0, 6);
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

		// Draw our second rect
		glUseProgram(shaderProgramG);
		glBindVertexArray(VAO[1]);
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
		glBindVertexArray(0);

		// Swap the screen buffers
		glfwSwapBuffers(window);
	}
	// Properly de-allocate all resources once they've outlived their purpose
	glDeleteVertexArrays(2, VAO);
	glDeleteBuffers(2, VBO);
	glDeleteBuffers(2, EBO);
	// Terminate GLFW, clearing any resources allocated by GLFW.
	glfwTerminate();
	return 0;
}

// Is called whenever a key is pressed/released via GLFW
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);
}

着色器

使用uniform定义一个水平偏移量，在顶点着色器中使用这个偏移量把三角形移动到屏幕右侧

xOffsetShader.cpp

#include "pch.h"

#include <iostream>

#include <GL/glew.h>
#include <GLFW/glfw3.h>

// Other includes
#include "Shader.h"


// Function prototypes
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode);

// Window dimensions
const GLuint WIDTH = 800, HEIGHT = 600;

// The MAIN function, from here we start the application and run the game loop
int main()
{
	// Init GLFW
	glfwInit();
	// Set all the required options for GLFW
	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);

	// Create a GLFWwindow object that we can use for GLFW's functions
	GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "LearnOpenGL", nullptr, nullptr);
	glfwMakeContextCurrent(window);

	// Set the required callback functions
	glfwSetKeyCallback(window, key_callback);

	// Set this to true so GLEW knows to use a modern approach to retrieving function pointers and extensions
	glewExperimental = GL_TRUE;
	// Initialize GLEW to setup the OpenGL Function pointers
	glewInit();

	// Define the viewport dimensions
	glViewport(0, 0, WIDTH, HEIGHT);


	// Build and compile our shader program
	Shader ourShader("../shaders/xOffset.vs", "../shaders/default.frag");


	// Set up vertex data (and buffer(s)) and attribute pointers
	GLfloat vertices[] = {
		// Positions         // Colors
		0.5f, -0.5f, 0.0f,   1.0f, 0.0f, 0.0f,  // Bottom Right
	    -0.5f, -0.5f, 0.0f,   0.0f, 1.0f, 0.0f,  // Bottom Left
		0.0f,  0.5f, 0.0f,   0.0f, 0.0f, 1.0f   // Top 
	};
	GLuint VBO, VAO;
	glGenVertexArrays(1, &VAO);
	glGenBuffers(1, &VBO);
	// Bind the Vertex Array Object first, then bind and set vertex buffer(s) and attribute pointer(s).
	glBindVertexArray(VAO);

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

	// Position attribute
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)0);
	glEnableVertexAttribArray(0);
	// Color attribute
	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
	glEnableVertexAttribArray(1);

	glBindVertexArray(0); // Unbind VAO

	float xOffset = 0;

	// Game loop
	while (!glfwWindowShouldClose(window))
	{
		// Check if any events have been activiated (key pressed, mouse moved etc.) and call corresponding response functions
		glfwPollEvents();

		// Render
		// Clear the colorbuffer
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		xOffset += 0.0001;
		ourShader.SetUniformFloat("xOffset", xOffset);

		// Draw the triangle
		ourShader.Use();
		glBindVertexArray(VAO);
		glDrawArrays(GL_TRIANGLES, 0, 3);
		glBindVertexArray(0);

		// Swap the screen buffers
		glfwSwapBuffers(window);
	}
	// Properly de-allocate all resources once they've outlived their purpose
	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	// Terminate GLFW, clearing any resources allocated by GLFW.
	glfwTerminate();
	return 0;
}

// Is called whenever a key is pressed/released via GLFW
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);
}

xOffset.vs

#version 330 core
layout (location = 0) in vec3 position;
layout (location = 1) in vec3 color;

out vec3 ourColor;

uniform float xOffset;

void main()
{
    gl_Position = vec4(position.x + xOffset, position.yz, 1.0f);
    ourColor = color;
}

default.frag

#version 330 core
in vec3 ourColor;

out vec4 color;

void main()
{
    color = vec4(ourColor, 1.0f);
}

shader.h

#ifndef SHADER_H
#define SHADER_H

#include <string>
#include <fstream>
#include <sstream>
#include <iostream>

#include <GL/glew.h>

class Shader
{
public:
	GLuint Program;
	// Constructor generates the shader on the fly
	Shader(const GLchar* vertexPath, const GLchar* fragmentPath)
	{
		// 1. Retrieve the vertex/fragment source code from filePath
		std::string vertexCode;
		std::string fragmentCode;
		std::ifstream vShaderFile;
		std::ifstream fShaderFile;
		// ensures ifstream objects can throw exceptions:
		vShaderFile.exceptions(std::ifstream::badbit);
		fShaderFile.exceptions(std::ifstream::badbit);
		try
		{
			// Open files
			vShaderFile.open(vertexPath);
			fShaderFile.open(fragmentPath);
			std::stringstream vShaderStream, fShaderStream;
			// Read file's buffer contents into streams
			vShaderStream << vShaderFile.rdbuf();
			fShaderStream << fShaderFile.rdbuf();
			// close file handlers
			vShaderFile.close();
			fShaderFile.close();
			// Convert stream into string
			vertexCode = vShaderStream.str();
			fragmentCode = fShaderStream.str();
		}
		catch (std::ifstream::failure e)
		{
			std::cout << "ERROR::SHADER::FILE_NOT_SUCCESFULLY_READ" << std::endl;
		}
		const GLchar* vShaderCode = vertexCode.c_str();
		const GLchar * fShaderCode = fragmentCode.c_str();
		// 2. Compile shaders
		GLuint vertex, fragment;
		GLint success;
		GLchar infoLog[512];
		// Vertex Shader
		vertex = glCreateShader(GL_VERTEX_SHADER);
		glShaderSource(vertex, 1, &vShaderCode, NULL);
		glCompileShader(vertex);
		// Print compile errors if any
		glGetShaderiv(vertex, GL_COMPILE_STATUS, &success);
		if (!success)
		{
			glGetShaderInfoLog(vertex, 512, NULL, infoLog);
			std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
		}
		// Fragment Shader
		fragment = glCreateShader(GL_FRAGMENT_SHADER);
		glShaderSource(fragment, 1, &fShaderCode, NULL);
		glCompileShader(fragment);
		// Print compile errors if any
		glGetShaderiv(fragment, GL_COMPILE_STATUS, &success);
		if (!success)
		{
			glGetShaderInfoLog(fragment, 512, NULL, infoLog);
			std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
		}
		// Shader Program
		this->Program = glCreateProgram();
		glAttachShader(this->Program, vertex);
		glAttachShader(this->Program, fragment);
		glLinkProgram(this->Program);
		// Print linking errors if any
		glGetProgramiv(this->Program, GL_LINK_STATUS, &success);
		if (!success)
		{
			glGetProgramInfoLog(this->Program, 512, NULL, infoLog);
			std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
		}
		// Delete the shaders as they're linked into our program now and no longer necessery
		glDeleteShader(vertex);
		glDeleteShader(fragment);

	}
	// Uses the current shader
	void Use()
	{
		glUseProgram(this->Program);
	}
	void SetUniformFloat(const char* name, float value) {
		GLint uniformLocation = glGetUniformLocation(Program, name);
		glUseProgram(Program);
		glUniform1f(uniformLocation, value);
	}
};

#endif