[转]OpenGL 通过VBO实现顶点数组绘制顶点

#include "stdlib.h"
#include <OpenGL/glext.h>
#include <GLUT/GLUT.h>  

#define BUFFER_OFFSET(bytes) ((GLubyte*) NULL + (bytes))
#define VERTICES 0
#define INDICES 1
#define NUM_BUFFERS 6
GLuint buffers[NUM_BUFFERS];  

GLfloat vertices[][3] = {
    {-1.0f,-1.0f,-1.0f},
    {1.0f,-1.0f,-1.0f},
    {1.0f,1.0f,-1.0f},
    {-1.0f,1.0f,-1.0f},
    {-1.0f,-1.0f,1.0f},
    {1.0f,-1.0f,1.0f},
    {1.0f,1.0f,1.0f},
    {-1.0f,1.0f,1.0f}
};
GLubyte indices[][4] = {
    {0,1,2,3},
    {4,7,6,5},
    {0,4,5,1},
    {3,2,6,7},
    {0,3,7,4},
    {1,5,6,2}
};  

GLfloat* bdata;  

void changeSize(int w, int h)
{
    glViewport(0,0,(GLsizei)w,(GLsizei)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0,(double)w/(double)h,0.01,30);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}  

void keyDown(unsigned char key, int x, int y)
{
    switch (key)
    {
        case‘b‘:
            bdata = (GLfloat*)glMapBuffer(GL_ARRAY_BUFFER,GL_READ_WRITE);
            for (int i =0; i <24; i ++)
            {
                *(bdata + i) *=1.1f;
            }
            glUnmapBuffer(GL_ARRAY_BUFFER);
            glutPostRedisplay();
            break;
    }
}  

void mouse(int button, int state, int x, int y)
{  

}
void display(void)
{
    glLoadIdentity();
    glTranslatef(0.0f,0.0f,-5.0f);
    glRotatef(30.0f,1.0f,1.0f,0.0f);  

   // 6. 绘制， 这个地方注意的是最后一个参数，这个与普通的非VBO最大的不同就在这里
    glDrawElements(GL_QUADS,24,GL_UNSIGNED_BYTE,BUFFER_OFFSET(0));
    //glDrawArrays(GL_TRIANGLE_FAN, 0, 8);
    glutSwapBuffers();
}  

void init(void)
{
    glClearColor(0.0f,0.0f,0.0f,0.0f);
    glShadeModel(GL_FLAT);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);  

    //1.  创建缓冲区对象，系统会自动创建缓动区标示符放入到buffers中，可以使用glIsBuffer()函数，判断一个标示符是否被使用
    glGenBuffers(NUM_BUFFERS ,buffers);
    //2.  激活缓冲区对象，绑定缓冲区对象表示未来选择的操作将影响哪个缓冲区。 如果要金融缓冲区对象，可以用0来作为缓冲区对象的标示符， 第一个参数target可以为GL_ARRAY_BUFFER,GL_ELEMENT_ARRAY_FUFFER
    glBindBuffer(GL_ARRAY_BUFFER,buffers[VERTICES]);
    //3. 用数据分配和初始化缓冲区对象
    glBufferData(GL_ARRAY_BUFFER,sizeof(vertices),vertices,GL_DYNAMIC_DRAW);
    //4. 指定相对于缓冲区起始位置的偏移量
    glVertexPointer(3,GL_FLOAT,0,BUFFER_OFFSET(0));
    //5.一定不要忘记启动
    glEnableClientState(GL_VERTEX_ARRAY);  

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,buffers[INDICES]);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER,sizeof(indices),indices,GL_STATIC_DRAW);
}  

int main(int argc, char* argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GL_DOUBLE | GLUT_RGBA | GLUT_DEPTH);
    glutInitWindowSize(512, 512);
    glutCreateWindow("Buffer Demo");
     init();
    glutReshapeFunc(changeSize);
    glutMouseFunc(mouse);
    glutKeyboardFunc(keyDown);
    glutDisplayFunc(display);  

    glutMainLoop();
    return 0;
} 

原文链接：OpenGL 通过VBO实现顶点数组绘制顶点

原文地址：https://www.cnblogs.com/rainbow70626/p/9030509.html