《OpenGL ES 2.0 Programming Guide》第8章 “最简单的Vertex Buffer Object”示例代码【C语言版】

由于《OpenGL ES 2.0 Programming Guide》原书并没有提供第8章的关于VBO的示例代码，书上的代码也只提到关键的步骤，网上的例子大都不够精简，为了加深理解，遂自己实现了一份最简单的C语言版本，希望能够帮助到同样喜欢OpenGL ES 2.0的同学。

废话不多说，直接上代码：

#include "esUtil.h"typedef struct{// Handle to a program objectGLuint programObject;GLint positionLoc;GLint colorLoc; // VertexBufferObject IdsGLuint vboIds[3];} UserData;#define VERTEX_POS_SIZE       3 // x, y and z#define VERTEX_COLOR_SIZE     4 // r, g, b, and aint Init ( ESContext *esContext ){UserData *userData = esContext->userData;const char vShaderStr[] ="attribute vec3 a_position;\n""attribute vec4 a_color;\n""varying vec4 v_color;\n""void main()\n""{\n""    v_color = a_color;\n""    gl_Position = vec4(a_position, 1.0);\n""}\n";const char fShaderStr[] ="precision mediump float;\n""varying vec4 v_color;\n""void main()\n""{\n""    gl_FragColor = v_color;\n""}\n" ;GLuint programObject;// Create the program objectprogramObject = esLoadProgram ( vShaderStr, fShaderStr );if ( programObject == 0 ){return GL_FALSE;}// Store the program objectuserData->programObject = programObject;userData->vboIds[0] = 0;// posuserData->vboIds[1] = 0;// coloruserData->vboIds[2] = 0;// indexuserData->positionLoc = glGetAttribLocation(userData->programObject, "a_position");userData->colorLoc = glGetAttribLocation(userData->programObject, "a_color");glClearColor ( 1.0f, 1.0f, 1.0f, 0.0f );return GL_TRUE;}void DrawPrimitiveWithVBOs ( ESContext *esContext,GLint numVertices, GLfloat *vertexPosBuf, GLfloat *vertexColorBuf,GLint *vtxStrides, GLint numIndices,GLushort *indices ){UserData *userData = esContext->userData;// vboIds[0] - used to store vertex position// vboIds[1] - used to store vertex color// vboIds[2] - used to store element indices// run only onceif ( userData->vboIds[0] == 0 && userData->vboIds[1] == 0 &&userData->vboIds[2] == 0 ){// Only allocate on the first drawglGenBuffers ( 3, userData->vboIds );glBindBuffer ( GL_ARRAY_BUFFER, userData->vboIds[0] );glBufferData ( GL_ARRAY_BUFFER, vtxStrides[0] * numVertices,vertexPosBuf, GL_STATIC_DRAW );glBindBuffer ( GL_ARRAY_BUFFER, userData->vboIds[1] );glBufferData ( GL_ARRAY_BUFFER, vtxStrides[1] * numVertices,vertexColorBuf, GL_STATIC_DRAW );glBindBuffer ( GL_ELEMENT_ARRAY_BUFFER, userData->vboIds[2] );glBufferData ( GL_ELEMENT_ARRAY_BUFFER,sizeof ( GLushort ) * numIndices,indices, GL_STATIC_DRAW );}glBindBuffer ( GL_ARRAY_BUFFER, userData->vboIds[0] );glVertexAttribPointer ( userData->positionLoc, VERTEX_POS_SIZE,GL_FLOAT, GL_FALSE, vtxStrides[0], 0 );glEnableVertexAttribArray ( userData->positionLoc );glBindBuffer ( GL_ARRAY_BUFFER, userData->vboIds[1] );glVertexAttribPointer ( userData->colorLoc,VERTEX_COLOR_SIZE,GL_FLOAT, GL_FALSE, vtxStrides[1], 0 );glEnableVertexAttribArray ( userData->colorLoc );glBindBuffer ( GL_ELEMENT_ARRAY_BUFFER, userData->vboIds[2] );glDrawElements ( GL_TRIANGLES, numIndices,GL_UNSIGNED_SHORT, 0 );eglSwapBuffers ( esContext->eglDisplay, esContext->eglSurface );// ☆// ---------------------------------------------------glDisableVertexAttribArray ( userData->positionLoc );glDisableVertexAttribArray ( userData->colorLoc );glBindBuffer ( GL_ARRAY_BUFFER, 0 );glBindBuffer ( GL_ELEMENT_ARRAY_BUFFER, 0 );}void Draw ( ESContext *esContext ){UserData *userData = esContext->userData;// 3 vertices, with (x,y,z) ,(r, g, b, a) per-vertexGLfloat vertexPos[3 * VERTEX_POS_SIZE] ={0.0f,  0.5f, 0.0f,         // v0-0.5f, -0.5f, 0.0f,        // v10.5f, -0.5f, 0.0f          // v2};GLfloat color[4 * VERTEX_COLOR_SIZE] ={1.0f, 0.0f, 0.0f, 1.0f,   // c00.0f, 1.0f, 0.0f, 1.0f,   // c10.0f, 0.0f, 1.0f, 1.0f    // c2};GLint vtxStrides[2] ={VERTEX_POS_SIZE * sizeof ( GLfloat ),VERTEX_COLOR_SIZE * sizeof ( GLfloat )};// Index buffer dataGLushort indices[3] = { 0, 1, 2 };//GLfloat *vtxBuf[2] = { vertexPos, color };glViewport ( 0, 0, esContext->width, esContext->height );glClear ( GL_COLOR_BUFFER_BIT );glUseProgram ( userData->programObject );DrawPrimitiveWithVBOs ( esContext, 3, vertexPos, color,vtxStrides, 3, indices );}void ShutDown ( ESContext *esContext ){UserData *userData = esContext->userData;glDeleteProgram ( userData->programObject );glDeleteBuffers ( 3, userData->vboIds );}int main ( int argc, char *argv[] ){ESContext esContext;UserData  userData;esInitContext ( &esContext );esContext.userData = &userData;esCreateWindow ( &esContext, "SimpleVBO", 320, 240, ES_WINDOW_RGB );if ( !Init ( &esContext ) ){return GL_FALSE;}esRegisterDrawFunc ( &esContext, Draw );esMainLoop ( &esContext );ShutDown ( &esContext );return GL_TRUE;}