使用opengl的geometry总结及其源代码

遇到两个问题：（1）如果geometry shader 文件不加上#version 450 core，compile shader source会报错；（2）使用GLFW创建窗口时，不添加glewExperimental = GL_TRUE，使用glGenVertexArrays(1, &vao)，直接崩溃（3）创建GL_GEOMETRY_SHADER，找不到该变量，更新glew包到1.3版本即可（4）使用glew 1.3版本和glut创建应用程序无法启动，使用glfw库来替代，原来的glut过于老了。源代码如下：basic.vert (vertex shader)

#version 450 core

in vec2 pos;

void main()
{
gl_Position = vec4(pos, 0.0, 1.0);
}

basic.geom(geometry shader)

#version 450 core

in vec2 pos;

void main()
{
gl_Position = vec4(pos, 0.0, 1.0);
}

basic.frag(fragment shader)

#version 450 core

out vec4 outColor;

void main()
{
outColor = vec4(1.0, 0.0, 0.0, 1.0);
}

读取文件FileManager.h/FileManager.cpp

class FileManager
{

public:
FileManager();
~FileManager();

public:

unsigned char* readDataFromFile(char* fn);

char* textFileRead(const char* fn);

int textFileWrite(char* fn, char* s);

};

#include "stdafx.h"
#include "FileManager.h"
#include <iostream>

FileManager::FileManager()
{
}

FileManager::~FileManager()
{
}

unsigned char* FileManager::readDataFromFile(char* fn)
{
FILE *fp;
unsigned char *content = NULL;

int count = 0;

if (fn != NULL) {
fopen_s(&fp, fn, "rb");

if (fp != NULL) {

fseek(fp, 0, SEEK_END);
count = ftell(fp);
rewind(fp);

if (count > 0) {
content = (unsigned char *)malloc(sizeof(unsigned char) * (count + 1));
count = fread(content, sizeof(unsigned char), count, fp);
content[count] = '\0';
}
fclose(fp);
}
}
return content;
}

char* FileManager::textFileRead(const char* fn)
{
FILE *fp;
char *content = NULL;

int count = 0;

if (fn != NULL) {
fopen_s(&fp, fn, "rt");

if (fp != NULL) {

fseek(fp, 0, SEEK_END);
count = ftell(fp);
rewind(fp);

if (count > 0) {
content = (char *)malloc(sizeof(char) * (count + 1));
count = fread(content, sizeof(char), count, fp);
content[count] = '\0';
}
fclose(fp);
}
}
return content;
}

int FileManager::textFileWrite(char* fn, char* s)
{
FILE *fp;
int status = 0;

if (fn != NULL) {
fopen_s(&fp, fn, "w");

if (fp != NULL) {

if (fwrite(s, sizeof(char), strlen(s), fp) == strlen(s))
status = 1;
fclose(fp);
}
}
return(status);
}

shader管理类ShaderManager.h/.cpp

#include <iostream>#include "FileManager.h"#include <gl/glew.h>#include <gl/GL.h>using namespace std;class ShaderManager{public:ShaderManager();~ShaderManager();public:void BuildShader(const char* VShaderFile,const char* GShaderFile,const char* FShaderFile);GLuint GetProgram();void ShowShaderInfo();public:GLuint m_vShader;GLuint m_fShader;GLuint m_gShader;GLuint m_Program;public:FileManager m_FileManager;};#include "stdafx.h"#include "ShaderManager.h"ShaderManager::ShaderManager(){}ShaderManager::~ShaderManager(){}void ShaderManager::ShowShaderInfo(){const GLubyte *renderer = glGetString(GL_RENDERER);const GLubyte *vendor = glGetString(GL_VENDOR);const GLubyte *version = glGetString(GL_VERSION);const GLubyte *glslVersion =glGetString(GL_SHADING_LANGUAGE_VERSION);GLint major, minor;glGetIntegerv(GL_MAJOR_VERSION, &major);glGetIntegerv(GL_MINOR_VERSION, &minor);cout << "GL Vendor    :" << vendor << endl;cout << "GL Renderer  : " << renderer << endl;cout << "GL Version (string)  : " << version << endl;cout << "GL Version (integer) : " << major << "." << minor << endl;cout << "GLSL Version : " << glslVersion << endl;}void ShaderManager::BuildShader(const char* VShaderFile,const char* GShaderFile,const char* FShaderFile){ShowShaderInfo();m_vShader = glCreateShader(GL_VERTEX_SHADER);if (m_vShader == 0){cerr << "Error: Create vertex shader failed!" << endl;return;}const GLchar* vShaderSource = m_FileManager.textFileRead(VShaderFile);const GLchar* vCodeArray[1] = {vShaderSource};glShaderSource(m_vShader, 1, vCodeArray, NULL);glCompileShader(m_vShader);GLint compileResult;glGetShaderiv(m_vShader, GL_COMPILE_STATUS, &compileResult);if (compileResult == GL_FALSE){cerr << "Error: Compile vertex shader failed!" << endl;return;}m_gShader = glCreateShader(GL_GEOMETRY_SHADER);if (0 == m_gShader){cerr << "ERROR: Create geometry failed!" << endl;return;}const GLchar* gShaderCode = m_FileManager.textFileRead(GShaderFile);const GLchar* gCodeArray[1] = { gShaderCode };glShaderSource(m_gShader, 1, gCodeArray, NULL);glCompileShader(m_gShader);glGetShaderiv(m_gShader, GL_COMPILE_STATUS, &compileResult);if (compileResult == GL_FALSE){cerr << "ERROR: compile geometry failed!" << endl;GLint logLen;glGetShaderiv(m_gShader, GL_INFO_LOG_LENGTH, &logLen);if (logLen > 0){char *log = (char *)malloc(logLen);GLsizei written;glGetShaderInfoLog(m_gShader, logLen, &written, log);cerr << "vertex shader compile log : " << endl;cerr << log << endl;free(log);}return;}m_fShader = glCreateShader(GL_FRAGMENT_SHADER);if (0 == m_fShader){cerr << "ERROR: Create fragment shader failed!" << endl;return;}const GLchar* fShaderCode = m_FileManager.textFileRead(FShaderFile);const GLchar* fCodeArray[1] = { fShaderCode };glShaderSource(m_fShader, 1, fCodeArray, NULL);glCompileShader(m_fShader);glGetShaderiv(m_fShader, GL_COMPILE_STATUS, &compileResult);if (compileResult == GL_FALSE){cerr << "Error: Compile fragment shader failed!" << endl;return;}m_Program = glCreateProgram();if (0 == m_Program){cerr << "ERROR: Create Program failed!" << endl;return;}glAttachShader(m_Program, m_vShader);glAttachShader(m_Program, m_gShader);glAttachShader(m_Program, m_fShader);glLinkProgram(m_Program);GLint linkStatus;glGetProgramiv(m_Program, GL_LINK_STATUS, &linkStatus);if (GL_FALSE == linkStatus){cerr << "ERROR: Link the program failed!" << endl;return;}glUseProgram(m_Program);}GLuint ShaderManager::GetProgram(){return m_Program;}

程序入口main.cpp

// testOpenGL.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include <iostream>#define  GLEW_STATIC#include "glew.h"#include "glfw3.h"#include "ShaderManager.h"const GLuint WIDTH = 800;const GLuint HEIGHT = 600;ShaderManager shaderManager;void key_callback(GLFWwindow* window, int key, int scancode, int action, int mode){std::cout << key << std::endl;if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS){glfwSetWindowShouldClose(window, GL_TRUE);}}void initData(){//GLuint vbo;glGenBuffers(1, &vbo);float points[] ={-0.45f, 0.45f,0.45f, 0.45f,0.45f, -0.45f,-0.45f, -0.45f,};glBindBuffer(GL_ARRAY_BUFFER, vbo);glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW);GLuint vao = 0;glGenVertexArrays(1, &vao);glBindVertexArray(vao);GLint posAttrib = glGetAttribLocation(shaderManager.GetProgram(), "pos");glEnableVertexAttribArray(posAttrib);glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 0, 0);}int _tmain(int argc, _TCHAR* argv[]){std::cout << "Starting GFLEW context, OpenGL 3.3" << std::endl;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);GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "Test GLFW Lib", NULL, NULL);if (window == NULL){std::cout << "Failed to create GLFW window!" << std::endl;glfwTerminate();return -1;}glfwMakeContextCurrent(window);glfwSetKeyCallback(window, key_callback);glewExperimental = GL_TRUE;if (glewInit() != GLEW_OK){std::cout << "Failed to initialize GLEW" << std::endl;return -1;}glViewport(0, 0, WIDTH, HEIGHT);// 创建shader对象shaderManager.BuildShader("basic.vert", "basic.geom", "basic.frag");initData();while (!glfwWindowShouldClose(window)){glfwPollEvents();glClearColor(0.2f, 0.3f, 0.3f, 1.0f);glClear(GL_COLOR_BUFFER_BIT);glDrawArrays(GL_POINTS, 0, 4);glfwSwapBuffers(window);}glfwTerminate();return 0;}