NeHe OpenGL Lesson45-Vertex Buffer Objects

This samples shows us how to put the mesh render data such as the vertex position, texture coordinates and even more vertex data upload into the video hardware. the samples what saw before that vertex data provided by the glVertex3f or glTexCoord2f commands, or vertex array. all those stuff are located in the main memory. they will be submitted to GPU as needed. but most of those vertex data that will not be modified and static cocould be allocated in the video memory at startup. this will save the data transferring time and vertex format GPU optimized. both of them will improve the render performance.

 

OpenGL Vertex Buffer Object extension Access

On windows, we need to use the OpenGL ARB extension to access those vertex buffer object functions. The following are the code that used to access OpenGL extensions:

g_fVBOSupported = IsExtensionSupported( "GL_ARB_vertex_buffer_object" );if( g_fVBOSupported ){    // Get Pointers To The GL Functions    glGenBuffersARB = (PFNGLGENBUFFERSARBPROC) wglGetProcAddress("glGenBuffersARB");    glBindBufferARB = (PFNGLBINDBUFFERARBPROC) wglGetProcAddress("glBindBufferARB");    glBufferDataARB = (PFNGLBUFFERDATAARBPROC) wglGetProcAddress("glBufferDataARB");    glDeleteBuffersARB = (PFNGLDELETEBUFFERSARBPROC) wglGetProcAddress("glDeleteBuffersARB");//...

 

Create Vertex buffer Objects

After the vertex data ready, then create the vertex buffer object, upload vertex data into the vertex buffer objects. The code as following:

// Generate And Bind The Vertex BufferglGenBuffersARB( 1, &m_nVBOVertices );                            // Get A Valid NameglBindBufferARB( GL_ARRAY_BUFFER_ARB, m_nVBOVertices );            // Bind The Buffer// Load The DataglBufferDataARB( GL_ARRAY_BUFFER_ARB, m_nVertexCount*3*sizeof(float),     m_pVertices, GL_STATIC_DRAW_ARB );// Generate And Bind The Texture Coordinate BufferglGenBuffersARB( 1, &m_nVBOTexCoords );                            // Get A Valid NameglBindBufferARB( GL_ARRAY_BUFFER_ARB, m_nVBOTexCoords );        // Bind The Buffer// Load The DataglBufferDataARB( GL_ARRAY_BUFFER_ARB, m_nVertexCount*2*sizeof(float),    m_pTexCoords, GL_STATIC_DRAW_ARB );

 

Render With Vertex Buffer Objects

// Enable PointersglEnableClientState( GL_VERTEX_ARRAY );        glEnableClientState( GL_TEXTURE_COORD_ARRAY );glBindBufferARB( GL_ARRAY_BUFFER_ARB, g_pMesh->m_nVBOVertices );// Set The Vertex Pointer To The Vertex BufferglVertexPointer( 3, GL_FLOAT, 0, (char *) NULL );        glBindBufferARB( GL_ARRAY_BUFFER_ARB, g_pMesh->m_nVBOTexCoords );// Set The TexCoord Pointer To The TexCoord BufferglTexCoordPointer( 2, GL_FLOAT, 0, (char *) NULL );        // Draw All Of The Triangles At OnceglDrawArrays( GL_TRIANGLES, 0, g_pMesh->m_nVertexCount );    // Disable PointersglDisableClientState( GL_VERTEX_ARRAY );        glDisableClientState( GL_TEXTURE_COORD_ARRAY );

 

Render With Vertex Array

The process render with vertex buffer objects is the same as render with vertex array. The code as following:

// Enable PointersglEnableClientState( GL_VERTEX_ARRAY );        glEnableClientState( GL_TEXTURE_COORD_ARRAY );glVertexPointer( 3, GL_FLOAT, 0, g_pMesh->m_pVertices ); glTexCoordPointer( 2, GL_FLOAT, 0, g_pMesh->m_pTexCoords );     // Draw All Of The Triangles At OnceglDrawArrays( GL_TRIANGLES, 0, g_pMesh->m_nVertexCount );    // Disable PointersglDisableClientState( GL_VERTEX_ARRAY );        glDisableClientState( GL_TEXTURE_COORD_ARRAY );

 

Release Vertex Buffer Objects

unsigned int nBuffers[2] = { m_nVBOVertices, m_nVBOTexCoords };glDeleteBuffersARB( 2, nBuffers );

 

The source code cocould be found here.