OpenGL初学者指南-优快云博客

本文链接：https://blog.youkuaiyun.com/u012363389/article/details/104229010

1. creating a window

http://learnopengl.com

1.glfw
download 32-BIT WINDOWS lib-Visio2015
2.glew lib release
window sysytem32 opengl32.lib
glew3.lib
projection

dll 动态连接可以不用和代码一起给打包，提交
lib 静态连接
所有组件
所有平台

c/c++ 一般 include
链接器一般其他程序式目录

2. hello windows

#include <isotream>
#define GLEW_STATIC
#include <GL/glew.h>
#include <GLFW/glfw3.h>
float vertices[] ={
-0.5f,-0.5f,0.0f;
 0.5f,-0.5f,0.0f;
 0.0f,-0.5f,0.0f
};
void processInput(GLFWwindow* window){
  if (glfwGetKey(window，GLFW_KEY_ESCAPE) == GLEW_PRESS){
     glfwSetWindowShouldClose(window,true);
}    
}

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

//Open GLFW Window
GLFWwindow* window = glfwCreatWindow(800,600,"My OpenGL",NULL,NULL);
if(window == NULL){
  printf("Open window failed!");
  glfwTerminate();
  return -1;
}

glfwMakeContextCurrent(window);

glewExperimental = true;
if(flewInit() != GLEW_OK){
  printf("Init GLEW failed!");
  glfwTerminate();
  return -1;
}

glViewport(0,0,800,600);

unsigned int VAO;
glGenVertexArrays(1,&VAO);
glBindVertexArrsy(VAO);

unsigned int VBO;
glGenBuffers(1,&VBO);
glBindBuffer(GL_ARRAY_BUFFER,VBO);

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

//GL_STATIC_DRAW  GL_DYNAMIC_DRAW GL_STREAM_DRAW
//ready your engines 一直运行 直到我们想停止
while(!glfwWindowsShouldClose(windows)){
   //input
   ProcessInput(window);
  
  //rendering commands  here
 
  //check and call event and swap the buffers
   glfwSwapBuffers(window);
   glfwPollEvents();//按键 操作 获取实现
}

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

glfwTerminate();
return 0;
}

glClear	类型
GL_COLOR_BUFFER_BIT
GL_DEPTH_BUFFER_BIT	深度
GL_STENCIL_BUFFER_BIT	遮罩

double buffer	WINDOW APPLICATIONS swap
the front buffer	show at the screen
the back buffer	the rendering commands

3. hello triangle

1.transforms 3d coordinates into 2d coordinates precise
2.transforms 2d coordinates into actual colored pixels aproximation

the small programs can easily be executed in parallel: shaders

graphics pipeline	abstract representation
vertex data[]	CPU 来的数据顶点
vertex shader	移动顶点操作顶点 (膨胀)
shade assembly	连接点线面
geometry shader	插点补点（增强纹理）
rasterization	取点变成一个一个点
fragment shader	补色材质 uv
tests and blending	测深度测遮挡如何融合

vertex data ——> fully rendered pixel

primitives
GL_POINTS
GL_TRIANGLES
GL_LINE_STRIP
primitives assembly

blender	*.obj
v	点坐标
vt	uv
vn	法向量 normal

vbo
vao
任何时候只会执行一个VAO，将VBO绑上VAO;也可以使用EBO对VAO进行说明

三角形绘制的缺省是逆时针方向

#include <isotream>
#define GLEW_STATIC
#include <GL/glew.h>
#include <GLFW/glfw3.h>
float vertices[] ={
-0.5f,-0.5f,0.0f;
 0.5f,-0.5f,0.0f;
 0.0f,-0.5f,0.0f;
 0.8f, 0.8f,0.0f
};

unsigned int indices[] ={
0,1,2,
2,1,3
};

const char* vertexShaderSource = 
"#version 330 core                                   \n"
"layout(location = 6) in vec3 aPos;                  \n"
"void main(){                                        \n"
"    gl_Position = vec4(aPos.x,aPos.y,aPos.z,1.0);}  \n";


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

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

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

//Open GLFW Window
GLFWwindow* window = glfwCreatWindow(800,600,"My OpenGL",NULL,NULL);
if(window == NULL){
  printf("Open window failed!");
  glfwTerminate();
  return -1;
}

glfwMakeContextCurrent(window);

glewExperimental = true;
if(glewInit() != GLEW_OK){
  printf("Init GLEW failed!");
  glfwTerminate();
  return -1;
}

glViewport(0,0,800,600);
//glEnable(GL_CULL_FACE);
//glCullFace(GL_BACK);
//glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);

//1.bind Vertex Array Object
unsigned int VAO;
glGenVertexArrays(1,&VAO);
glBindVertexArray(VAO);

//2.copy our vertices array in a buffer for OpenGL to use
unsigned int VBO;
glGenBuffers(1,&VBO);
glBindBuffer(GL_ARRAY_BUFFER,VBO);
glBufferData(GL_ARRAY_BUFFER,sizeof(vertices),vertices,GL_STATIC_DRAW);

unsigned int EBO;
glGenBuffers(1,&EBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,EBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER,sizeof(indices),indices,GL_STATIC_DRAW);


unsigned int vertexShader;
vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader,1,&vertexShaderSource,NULL):
glCompileShader(vertexShader);

unsigned int fragmentShader;
fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader,1,&fragmentShaderSource,NULL):
glCompileShader(fragmentShader);


unsigned int shaderProgram;
shaderProgram = glCreatProgram();
glAttachShader(shaderProgram,vertexShader);
glAttachShader(shaderProgram,fragmentShader);
glLinkProgram():

//3.then set our vertex attributes pointers
glVertexAttribPointer(6,3,GL_FLOAT,GL_FALSE,3*sizeof(float),void*(0));
//attribPointer:location,number,类型，是否标准化到-1:1，几个数一组，偏移量offset
glEnableVertexAttribArray(6);

//GL_STATIC_DRAW  GL_DYNAMIC_DRAW GL_STREAM_DRAW
//ready your engines 一直运行 直到我们想停止
while(!glfwWindowsShouldClose(windows)){
   //input
   ProcessInput(window);
  
  //rendering commands  here
  glClearColor(0.2f,0.3f,0.3f,1.0f);
  glClear(GL_COLOR_BUFFER_BIT);

  //4.draw the object
  glBindVertexArray(VAO);
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,EBO);
  glUseProgram(shaderProgram);
  //glDrawArrays(GL_TRIANGLES,0,6);
  glDrawElements(GL_TRIANGLES,6,GL_UNSIGNED_INT,0);
 
  //check and call event and swap the buffers
   glfwSwapBuffers(window);
   glfwPollEvents();//按键 操作 获取实现
}

glfwTerminate();
return 0;
}