OpenGL Insights

28. Asynchronous Buffer Transfers 401

const int buffer_number = frame_number++ % 3;

// Wait until buffer is free to use, in most cases this should not wait

// because we are using three buffers in chain , glClientWaitSync

// function can be used for check if the TIMEOUT is zero

GLenum result = glClientWaitSync(fences[ buffer_number], 0, TIMEOUT );

if ( result == GL_TIMEOUT_EXPIRED || result == GL_WAIT_FAILED)

{

// Something is wrong

}

glDeleteSync(fences [ buffer_number]);

glBindBuffer(GL_ARRAY_BUFFER , buffers [ buffer_number]);

void *ptr = glMapBufferRange(GL_ARRAY_BUFFER , offset , size, GL_MAP_WRITE_BIT | ←

GL_MAP_UNSYNCHRONIZED_BIT);

// Fill ptr with ...