OpenGL画三角形--2

程序员文章站 2022-07-04 11:06:11

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–中间过程代码未进行封装–
1.非索引：glDrawArrays(GL_TRIANGLES, 0, 3);
一步一步画出三角形，shader代码是硬编码。
参考：这里

//顺序不能错
#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include <iostream>

using namespace std;

void framebuffer_size_callback(GLFWwindow* windwo, int width, int height);
void processInput(GLFWwindow* window);

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


//硬编码顶点、片元源码
const char* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
"   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";

const char* fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
"   FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0);\n"
"}\0";


int main()
{
	//init
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

#ifdef __APPLE__
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif

	//create window object
	GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
	if (window == NULL)
	{
		cout << "Failed to create GLFW window!" << endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);
	//regiester callback
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

	//init GLAD
	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		cout << "Failed to init GLAD!" << endl;
		return -1;
	}


	//configure options
	//设置线框模式
	//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

	//关闭线框模式：填充
	//glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

	//compile and build shader program

	//1.create vertex shader
	unsigned int vertexShader;
	vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);

	//error check
	int success;
	char infoLog[512];
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
		cout << "error::vertex compile failed!\n" << infoLog << endl;
	}

	//2.create fragment shader
	unsigned int fragmentShader;
	fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
	glCompileShader(fragmentShader);

	//error check
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		cout << "error::fragment compile failed!\n" << infoLog << endl;
	}

	//3.link shader
	unsigned int shaderProgram;
	shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);

	//error check
	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
	}

	//4.delete shader
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);

	//vertex data
	float vertices[] = {
	-0.5f, -0.5f, 0.0f,
	 0.5f, -0.5f, 0.0f,
	 0.0f,  0.5f, 0.0f
	};

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

	//OpenGL核心模式必须用VAO才能显示要画的图形
	glBindVertexArray(VAO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);

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

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
	//set pointer
	glEnableVertexAttribArray(0);

	//render loop
	while (!glfwWindowShouldClose(window))
	{
		//input
		processInput(window);

		//render
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		//use shader program
		glUseProgram(shaderProgram);
		glBindVertexArray(VAO);
		glDrawArrays(GL_TRIANGLES, 0, 3);

		//swap buffer
		glfwSwapBuffers(window);
		//call events
		glfwPollEvents();
	}

	//clear
	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	glDeleteProgram(shaderProgram);

	//terminate software
	glfwTerminate();
	return 0;
}


void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
	glViewport(0, 0, SCR_HEIGHT, SCR_HEIGHT);
}

void processInput(GLFWwindow* window)
{
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
	{
		glfwSetWindowShouldClose(window, true);
	}
}

2.索引绘制：glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

//顺序不能错
#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include <iostream>

using namespace std;

void framebuffer_size_callback(GLFWwindow* windwo, int width, int height);
void processInput(GLFWwindow* window);

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


//硬编码顶点、片元源码
const char* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
"   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";

const char* fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
"   FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0);\n"
"}\0";


int main()
{
	//init
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

#ifdef __APPLE__
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif

	//create window object
	GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
	if (window == NULL)
	{
		cout << "Failed to create GLFW window!" << endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);
	//regiester callback
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

	//init GLAD
	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		cout << "Failed to init GLAD!" << endl;
		return -1;
	}


	//configure options
	//设置线框模式
	//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

	//关闭线框模式：填充
	//glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

	//compile and build shader program

	//1.create vertex shader
	unsigned int vertexShader;
	vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);

	//error check
	int success;
	char infoLog[512];
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
		cout << "error::vertex compile failed!\n" << infoLog << endl;
	}

	//2.create fragment shader
	unsigned int fragmentShader;
	fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
	glCompileShader(fragmentShader);

	//error check
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		cout << "error::fragment compile failed!\n" << infoLog << endl;
	}

	//3.link shader
	unsigned int shaderProgram;
	shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);

	//error check
	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
	}

	//4.delete shader
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);

	//vertex data
	float vertices[] = {
	0.5f, 0.5f, 0.0f,   // 右上角
	0.5f, -0.5f, 0.0f,  // 右下角
	-0.5f, -0.5f, 0.0f, // 左下角
	-0.5f, 0.5f, 0.0f   // 左上角
	};

	unsigned int indices[] = { // 注意索引从0开始! 
		0, 1, 3, // 第一个三角形
		1, 2, 3  // 第二个三角形
	};

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

	//OpenGL核心模式必须用VAO才能显示要画的图形
	glBindVertexArray(VAO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);

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

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
	//set pointer
	glEnableVertexAttribArray(0);	

	//create element array buffer
	//创建的索引缓冲会绑定到顶点数组缓冲（只要没有解绑就会自动绑定，或者说自动绑定到上次绑定的数组缓冲(可能会出错！)）
	//如果之前有glBindVertexArray(0);代表解除绑定，或者未绑定过数组缓冲，则会报错，绑定不了
	unsigned int EBO;
	glGenBuffers(1, &EBO);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

	//unbind：解除绑定
	//glBindVertexArray(0);

	//render loop
	while (!glfwWindowShouldClose(window))
	{
		//input
		processInput(window);

		//render
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		//use shader program
		glUseProgram(shaderProgram);
		glBindVertexArray(VAO);

		//glDrawArrays(GL_TRIANGLES, 0, 3);
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

		//swap buffer
		glfwSwapBuffers(window);
		//call events
		glfwPollEvents();
	}

	//clear
	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	glDeleteProgram(shaderProgram);

	//terminate software
	glfwTerminate();
	return 0;
}


void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
	glViewport(0, 0, SCR_HEIGHT, SCR_HEIGHT);
}

void processInput(GLFWwindow* window)
{
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
	{
		glfwSetWindowShouldClose(window, true);
	}
}

练习题：画两个三角形和用不同颜色的片元着色器

//顺序不能错
#include <glad/glad.h>
#include <GLFW/glfw3.h>

#include <iostream>

using namespace std;

void framebuffer_size_callback(GLFWwindow* windwo, int width, int height);
void processInput(GLFWwindow* window);

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


//硬编码顶点、片元源码
const char* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
"   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";

const char* fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
"   FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0);\n"
"}\0";

const char* fragmentShaderSource2 = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
"   FragColor = vec4(1.0f, 0.0f, 0.0f, 1.0);\n"
"}\0";



int main()
{
	//init
	glfwInit();
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

#ifdef __APPLE__
	glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif

	//create window object
	GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
	if (window == NULL)
	{
		cout << "Failed to create GLFW window!" << endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);
	//regiester callback
	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

	//init GLAD
	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
	{
		cout << "Failed to init GLAD!" << endl;
		return -1;
	}


	//configure options
	//设置线框模式
	//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

	//关闭线框模式：填充
	//glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

	//compile and build shader program

	//1.create vertex shader
	unsigned int vertexShader;
	vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);

	//error check
	int success;
	char infoLog[512];
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
		cout << "error::vertex compile failed!\n" << infoLog << endl;
	}

	//2.create fragment shader
	unsigned int fragmentShader;
	fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
	glCompileShader(fragmentShader);

	//2.1.create fragment shader
	unsigned int fragmentShader2;
	fragmentShader2 = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader2, 1, &fragmentShaderSource2, NULL);
	glCompileShader(fragmentShader2);

	//error check
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		cout << "error::fragment compile failed!\n" << infoLog << endl;
	}

	//3.link shader
	unsigned int shaderProgram,shaderProgram2;
	shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);

	shaderProgram2 = glCreateProgram();
	glAttachShader(shaderProgram2,vertexShader);
	glAttachShader(shaderProgram2,fragmentShader2);
	glLinkProgram(shaderProgram2);

	//error check
	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
	}

	//4.delete shader
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);

	float firstTriangle[] = {
		-0.9f, -0.5f, 0.0f,  // left 
		-0.0f, -0.5f, 0.0f,  // right
		-0.45f, 0.5f, 0.0f,  // top 
	};
	float secondTriangle[] = {
		0.0f, -0.5f, 0.0f,  // left
		0.9f, -0.5f, 0.0f,  // right
		0.45f, 0.5f, 0.0f   // top 
	};	

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

	//OpenGL核心模式必须用VAO才能显示要画的图形
	glBindVertexArray(VAO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);

	glBufferData(GL_ARRAY_BUFFER, sizeof(firstTriangle), firstTriangle, GL_STATIC_DRAW);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
	//set pointer
	glEnableVertexAttribArray(0);	

	//set vertex
	unsigned int VBO2, VAO2;
	glGenBuffers(1, &VBO2);
	glGenVertexArrays(1, &VAO2);

	//OpenGL核心模式必须用VAO才能显示要画的图形
	glBindVertexArray(VAO2);
	glBindBuffer(GL_ARRAY_BUFFER, VBO2);

	glBufferData(GL_ARRAY_BUFFER, sizeof(secondTriangle), secondTriangle, GL_STATIC_DRAW);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
	//set pointer
	glEnableVertexAttribArray(0);
	

	//unbind：解除绑定
	//glBindVertexArray(0);

	//render loop
	while (!glfwWindowShouldClose(window))
	{
		//input
		processInput(window);

		//render
		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		//use shader program
		glUseProgram(shaderProgram);
		glBindVertexArray(VAO);

		glDrawArrays(GL_TRIANGLES, 0, 3);
		//glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);

		glUseProgram(shaderProgram2);
		glBindVertexArray(VAO2);

		glDrawArrays(GL_TRIANGLES, 0, 3);

		//swap buffer
		glfwSwapBuffers(window);
		//call events
		glfwPollEvents();
	}

	//clear
	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	glDeleteProgram(shaderProgram);

	//terminate software
	glfwTerminate();
	return 0;
}


void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
	glViewport(0, 0, SCR_HEIGHT, SCR_HEIGHT);
}

void processInput(GLFWwindow* window)
{
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
	{
		glfwSetWindowShouldClose(window, true);
	}
}

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