OpenGL笔记九之彩色三角形与重心插值算法

—— 2024-07-07 晚上

bilibili赵新政老师的教程看后笔记

code review!

1.运行

3.main.cpp

代码

#include <iostream>

#define DEBUG

//注意：glad头文件必须在glfw引用之前引用
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <string>
#include <assert.h>//断言
#include "wrapper/checkError.h"
#include "application/Application.h"

/*
*┌────────────────────────────────────────────────┐
*│　目	   标： 学习彩色三角形绘制
*│　讲    师： 赵新政(Carma Zhao)
*│　拆分目标：
*│			vs：
*│　		1 在vs当中获取layout为1的属性-color
*			2 在vs当中声明out类型变量，向后传递颜色数据
*			3 给out类型变量赋值
*			fs：
*			1 在fs当中声明in类型变量，接收前方阶段传递的颜色数据
*			2 将获取的in类型颜色数据，赋值给fragColor
*└────────────────────────────────────────────────┘
*/

GLuint vao, program;


void OnResize(int width, int height) {
	GL_CALL(glViewport(0, 0, width, height));
	std::cout << "OnResize" << std::endl;
}

void OnKey(int key, int action, int mods) {
	std::cout << key << std::endl;
}



void prepareVAO() {
	//1 准备positions colors
	float positions[] = {
		-0.5f, -0.5f, 0.0f,
		0.5f, -0.5f, 0.0f,
		0.0f,  0.5f, 0.0f,
	};

	float colors[] = {
		1.0f, 0.0f,0.0f,
		0.0f, 1.0f,0.0f,
		0.0f, 0.0f,1.0f
	};

	unsigned int indices[] = {
		0, 1, 2
	};

	//2 VBO创建
	GLuint posVbo, colorVbo;
	glGenBuffers(1, &posVbo);
	glBindBuffer(GL_ARRAY_BUFFER, posVbo);
	glBufferData(GL_ARRAY_BUFFER, sizeof(positions), positions, GL_STATIC_DRAW);

	glGenBuffers(1, &colorVbo);
	glBindBuffer(GL_ARRAY_BUFFER, colorVbo);
	glBufferData(GL_ARRAY_BUFFER, sizeof(colors), colors, GL_STATIC_DRAW);

	//3 EBO创建
	GLuint ebo;
	glGenBuffers(1, &ebo);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

	//4 VAO创建
	glGenVertexArrays(1, &vao);
	glBindVertexArray(vao);

	//5 绑定vbo ebo 加入属性描述信息
	//5.1 加入位置属性描述信息
	glBindBuffer(GL_ARRAY_BUFFER, posVbo);
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 3, (void*)0);

	//5.2 加入颜色属性描述数据
	glBindBuffer(GL_ARRAY_BUFFER, colorVbo);
	glEnableVertexAttribArray(1);
	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 3, (void*)0);

	//5.3 加入ebo到当前的vao
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);

	glBindVertexArray(0);
}

void prepareShader() {
	//1 完成vs与fs的源代码，并且装入字符串
	const char* vertexShaderSource =
		"#version 330 core\n"
		"layout (location = 0) in vec3 aPos;\n"
		"layout (location = 1) in vec3 aColor;\n"
		"out vec3 color;\n"
		"void main()\n"
		"{\n"
		"   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
		"   color = aColor;\n"
		"}\0";
	const char* fragmentShaderSource =
		"#version 330 core\n"
		"out vec4 FragColor;\n"
		"in vec3 color;\n"
		"void main()\n"
		"{\n"
		"   FragColor = vec4(color, 1.0f);\n"
		"}\n\0";


	//2 创建Shader程序（vs、fs）
	GLuint vertex, fragment;
	vertex = glCreateShader(GL_VERTEX_SHADER);
	fragment = glCreateShader(GL_FRAGMENT_SHADER);


	//3 为shader程序输入shader代码
	glShaderSource(vertex, 1, &vertexShaderSource, NULL);
	glShaderSource(fragment, 1, &fragmentShaderSource, NULL);

	int success = 0;
	char infoLog[1024];
	//4 执行shader代码编译 
	glCompileShader(vertex);
	//检查vertex编译结果
	glGetShaderiv(vertex, GL_COMPILE_STATUS, &success);
	if (!success) {
		glGetShaderInfoLog(vertex, 1024, NULL, infoLog);
		std::cout << "Error: SHADER COMPILE ERROR --VERTEX" << "\n" << infoLog << std::endl;
	}

	glCompileShader(fragment);
	//检查fragment编译结果
	glGetShaderiv(fragment, GL_COMPILE_STATUS, &success);
	if (!success) {
		glGetShaderInfoLog(fragment, 1024, NULL, infoLog);
		std::cout << "Error: SHADER COMPILE ERROR --FRAGMENT" << "\n" << infoLog << std::endl;
	}

	//5 创建一个Program壳子
	program = glCreateProgram();

	//6 将vs与fs编译好的结果放到program这个壳子里
	glAttachShader(program, vertex);
	glAttachShader(program, fragment);

	//7 执行program的链接操作，形成最终可执行shader程序
	glLinkProgram(program);

	//检查链接错误
	glGetProgramiv(program, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(program, 1024, NULL, infoLog);
		std::cout << "Error: SHADER LINK ERROR " << "\n" << infoLog << std::endl;
	}

	//清理
	glDeleteShader(vertex);
	glDeleteShader(fragment);
}

void render() {
	//执行opengl画布清理操作
	GL_CALL(glClear(GL_COLOR_BUFFER_BIT));

	//1 绑定当前的program
	GL_CALL(glUseProgram(program));

	//2 绑定当前的vao
	GL_CALL(glBindVertexArray(vao));
	//3 发出绘制指令
//	glDrawArrays(GL_LINE_STRIP, 0, 6);
	glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_INT, 0);
	glBindVertexArray(0);
}


int main() {
	if (!app->init(800, 600)) {
		return -1;
	}

	app->setResizeCallback(OnResize);
	app->setKeyBoardCallback(OnKey);

	//设置opengl视口以及清理颜色
	GL_CALL(glViewport(0, 0, 800, 600));
	GL_CALL(glClearColor(0.2f, 0.3f, 0.3f, 1.0f));

	prepareShader();
	prepareVAO();
	while (app->update()) {
		render();
	}

	app->destroy();

	return 0;
}