OpenGL（二十四） VAO、VBO和着色器使用示例

1. 新建一个工程，新建一个头文件Shader.h，内容如下：

#ifndef _SHADER_H_
#define _SHADER_H_

#include <vector>
#include <string>
#include <cstring>
#include <GL/glew.h>

class Shader
{
public:
static GLuint createShader(GLenum eShaderType, const std::string &strShaderFile);
static GLuint createShader(GLenum eShaderType, const char* fileName);
static GLuint createProgram(const std::vector<GLuint> &shaderList);
};

#endif

2. 相应的新建一个源文件Shader.h，内容如下：

#include <fstream>
#include <sstream>
#include "shader.h"

//从字符串流构造着色器对象
GLuint Shader::createShader(GLenum eShaderType, const std::string &strShaderFile)
{
GLuint shader = glCreateShader(eShaderType);//根据类型创建shader
const char * strFileData = strShaderFile.c_str();
glShaderSource(shader, 1, &strFileData, NULL);//绑定shader字符串
glCompileShader(shader);//编译shader
//检查shader状态
GLint status;
glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
if (status == GL_FALSE)
{
GLint infoLogLength;
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLogLength);
GLchar *strInfoLog = new GLchar[infoLogLength + 1];
glGetShaderInfoLog(shader, infoLogLength, NULL, strInfoLog);
const char * strShaderType = NULL;
switch (eShaderType)
{
case GL_VERTEX_SHADER: strShaderType = "vertex"; break;
case GL_GEOMETRY_SHADER: strShaderType = "geometry"; break;
case GL_FRAGMENT_SHADER: strShaderType = "fragment"; break;
}
fprintf(stderr, "Compile failure in %s shader:\n%s\n", strShaderType, strInfoLog);
delete[] strInfoLog;
}
return shader;
}

//从文件构造着色器对象
GLuint Shader::createShader(GLenum eShaderType, const char* fileName)
{
std::ifstream infile(fileName);
if (!infile)
{
fprintf(stderr, "Could not open file : %s for reading.", fileName);
return 0;
}
std::stringstream  buffer;
buffer << infile.rdbuf();
infile.close();
return Shader::createShader(eShaderType, buffer.str());
}

//构造着色器程序对象
GLuint Shader::createProgram(const std::vector<GLuint> &shaderList)
{
GLuint programId = glCreateProgram();//创建program
for (std::vector<GLuint>::size_type iLoop = 0; iLoop < shaderList.size(); iLoop++)
glAttachShader(programId, shaderList[iLoop]);//绑定shader

glLinkProgram(programId);//链接shader
//检查program状态
GLint status;
glGetProgramiv(programId, GL_LINK_STATUS, &status);
if (status == GL_FALSE)
{
GLint infoLogLength;
glGetProgramiv(programId, GL_INFO_LOG_LENGTH, &infoLogLength);

GLchar *strInfoLog = new GLchar[infoLogLength + 1];
glGetProgramInfoLog(programId, infoLogLength, NULL, strInfoLog);
fprintf(stderr, "Linker failure: %s\n", strInfoLog);
delete[] strInfoLog;
}
for (size_t iLoop = 0; iLoop < shaderList.size(); iLoop++)
glDetachShader(programId, shaderList[iLoop]);
return programId;
}

3. Shader.h和Shader.cpp文件主要作用是构建了一个着色器，以下是主要的工程实现代码，新建一个源文件VaoVboTest.cpp，内容如下：

//使用VAO VBO和着色器绘制三角形(现代OpenGL方式)
#include <string>
#include <vector>
#include <GL/glew.h>
#include <GL/freeglut.h>
#include "Shader.h"

using namespace std;

void userInit();
void reshape(int w, int h);
void display(void);
void keyboardAction(unsigned char key, int x, int y);

GLuint vboId;//vertex buffer object句柄
GLuint vaoId;//vertext array object句柄
GLuint programId;//shader program 句柄

int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE);
glutInitWindowPosition(100, 100);
glutInitWindowSize(512, 512);
glutCreateWindow("Triangle demo");

glewInit();
userInit();
glutReshapeFunc(reshape);
glutDisplayFunc(display);
glutKeyboardFunc(keyboardAction);
glutMainLoop();
return 0;
}

//自定义初始化函数
void userInit()
{
glClearColor(0.0, 0.0, 0.0, 0.0);
//创建顶点数据
const GLfloat vertices[] = {
-0.5f,-0.5f,0.0f,1.0f,
0.5f,0.0f,0.0f,1.0f,
0.0f,0.5f,0.0f,1.0f,
};

//创建vertex array object对象
glGenVertexArrays(1, &vaoId);
glBindVertexArray(vaoId);

//创建vertex buffer object对象
glGenBuffers(1, &vboId);
glBindBuffer(GL_ARRAY_BUFFER, vboId);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, 0);

//创建着色器
const std::string vertexStr(
"#version 450\n"
"layout(location=0) in vec4 position;\n"
"void main()\n"
"{gl_Position = position;}\n"
);

const std::string fragmentStr(
"#version 450\n"
"out vec4 outputColor;\n"
"void main()\n"
"{outputColor = vec4(1.0f,1.0f,0.0f,1.0f);}\n"
);

std::vector<GLuint> idVector;
idVector.push_back(Shader::createShader(GL_VERTEX_SHADER, vertexStr));
idVector.push_back(Shader::createShader(GL_FRAGMENT_SHADER, fragmentStr));
programId = Shader::createProgram(idVector);
}

//调整窗口大小回调函数
void reshape(int w, int h)
{
glViewport(0, 0, (GLsizei)w, (GLsizei)h);
}

//绘制回调函数
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(programId);
glBindBuffer(GL_ARRAY_BUFFER, vboId);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
glDrawArrays(GL_TRIANGLES, 0, 3);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glUseProgram(0);
glDisableVertexAttribArray(0);
glutSwapBuffers();
}

//键盘按键回调函数
void keyboardAction(unsigned char key, int x, int y)
{
switch (key)
{
case 033:  // Escape key
exit(EXIT_SUCCESS);
break;
}
}

不要忘了在链接器->输入->附加依赖项里添加 “glew32.lib”。完成之后编译生成效果：