角形并用 shader 改变颜色"/>
在 opengl 中画出三角形并用 shader 改变颜色
/*
glew.h 源代码中的一些宏定义
typedef unsigned int GLenum;
typedef unsigned int GLbitfield;
typedef unsigned int GLuint;
typedef int GLint;
typedef int GLsizei;
typedef unsigned char GLboolean;
typedef signed char GLbyte;
typedef short GLshort;
typedef unsigned char GLubyte;
typedef unsigned short GLushort;
typedef unsigned long GLulong;
typedef float GLfloat;
typedef float GLclampf;
typedef double GLdouble;
typedef double GLclampd;
typedef void GLvoid;
*/
#include <iostream>
#define GLEW_STATIC
#include <GL/glew.h>
#include <GLFW/glfw3.h>
void key_callback(GLFWwindow *windows, int key, int scancode, int actin, int mode);
const GLuint WIDTH = 800, HEIGHT = 600;
//Shaders
const GLchar *vertexShaderSource = "#version 330 core\n"
" \n"
"layout (location = 0) in vec3 position;\n"
"\n"
"void main()\n"
"{\n"
" gl_Position = vec4(position.x, position.y, position.z, 1.0);\n"
"}";
const GLchar *fragmentShaderSource = "#version 330 core\n"
"out vec4 color;\n"
"void main()\n"
"{\n"
"color = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
"}\n\0";
const GLchar* fragmentShaderSource2 = "#version 330 core\n"
"out vec4 color;\n"
"void main()\n"
"{\n"
"color = vec4(1.0f, 1.0f, 0.0f, 1.0f); // The color yellow \n"
"}\n\0";
int main() {glfwInit();
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);
//返回指向 GLFWwindow 对象的指针，参数有五个，前两个是高和宽，中间是窗口的名字，后两个是模式和共享的选项，
//现在都是 null， 注意 nullptr 是 c++11 的语法
GLFWwindow *window = glfwCreateWindow(WIDTH, HEIGHT, "OpenGL", nullptr, nullptr);
glfwMakeContextCurrent(window); //用 GLFW 在当前现成创建主环境
glewExperimental = GL_TRUE;//将其设为 true 来使 glew 用更新的技术来处理 opengl 函数
glewInit();//初始化glew
//用 viewport 来定义尺寸来使其能在高 dpi 屏幕上也能正常工作
int width, height;
glfwGetFramebufferSize(window, &width, &height);
glViewport(0, 0, width, height);
//创建 vertexShader,glShaderSource 将 shader 的代码给定到指定的 shader 中，返回对象的 ID
//glCompileShader 来编译.
GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
//当编译 Shader 错误时报错
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 ，同上
GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
// 检查编译错误
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success) {glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
}// Fragment shader ，同上
GLuint fragmentShader2 = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader2, 1, &fragmentShaderSource2, NULL);
glCompileShader(fragmentShader2);
// Check for compile time errors
glGetShaderiv(fragmentShader2, GL_COMPILE_STATUS, &success);
if (!success) {glGetShaderInfoLog(fragmentShader2, 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);
//检查 link 是否出错
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
}GLuint shaderProgram2 = glCreateProgram();
glAttachShader(shaderProgram2, vertexShader);
glAttachShader(shaderProgram2, fragmentShader2);
glLinkProgram(shaderProgram2);
//检查 link 是否出错
glGetProgramiv(shaderProgram2, GL_LINK_STATUS, &success);
if (!success) {glGetProgramInfoLog(shaderProgram2, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
}//用完后删除 Shader
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
glDeleteShader(fragmentShader2);
//定义点数据
GLfloat vertices1[] = {0.0f, -0.5f, 0.0f,
1.0f, -0.5f, 0.0f,
0.5f, 0.5f, 0.0f,
};
GLfloat vertices2[] = {0.0f, -0.5f, 0.0f,
-1.0, -0.5f, 0.0f,
-0.5f, 0.5f, 0.0f
};
GLuint VBOs[2], VAOs[2];
//第一个三角形
glGenVertexArrays(1, &VAOs[0]);
glGenBuffers(1, &VBOs[0]);
glBindVertexArray(VAOs[0]);
glBindBuffer(GL_ARRAY_BUFFER, VBOs[0]); //绑定 VBO
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices1), vertices1, GL_STATIC_DRAW);//将定义好的点放入缓存中,
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat),
(GLvoid *) 0);//定义如何使用点数据，第一个参数是 location，确定我们要设置哪些点属性
glEnableVertexAttribArray(0); //使 location 为 0 的点可以使用属性，默认是关闭的
glBindBuffer(GL_ARRAY_BUFFER, 0);//解绑 VBO
glBindVertexArray(0);//解绑 VAO
//第二个三角形
glGenVertexArrays(1, &VAOs[1]);
glGenBuffers(1, &VBOs[1]);
glBindVertexArray(VAOs[1]);
glBindBuffer(GL_ARRAY_BUFFER, VBOs[1]); //绑定 VBO
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);//将定义好的点放入缓存中,
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat),
(GLvoid *) 0);//定义如何使用点数据，第一个参数是 location，确定我们要设置哪些点属性
glEnableVertexAttribArray(0); //使 location 为 0 的点可以使用属性，默认是关闭的
glBindBuffer(GL_ARRAY_BUFFER, 0);//解绑 VBO
glBindVertexArray(0);//解绑 VAO
//游戏循环
while (!glfwWindowShouldClose(window)) {//检查是否有事件发生
glfwPollEvents();
//重置颜色
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
//运行shaderProgram
glUseProgram(shaderProgram);
glBindVertexArray(VAOs[0]);
//画出三角形
glDrawArrays(GL_TRIANGLES, 0, 3);
glUseProgram(shaderProgram2);
glBindVertexArray(VAOs[1]);
//画出三角形
glDrawArrays(GL_TRIANGLES, 0, 3);
glBindVertexArray(0);
//交换缓存
glfwSwapBuffers(window);
}glDeleteVertexArrays(2, VAOs);
glDeleteBuffers(2, VBOs);
glfwTerminate();
return 0;
}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);
}
这是 learnopengl 里的习题
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在 opengl 中画出三角形并用 shader 改变颜色
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