question: private void present ( ) { glUseProgram ( quadProgram ) ; glBindBuffer ( GL_ARRAY_BUFFER , vbo ) ; glActiveTexture ( GL_TEXTURE0 ) ; glBindTexture ( GL_TEXTURE_2D , tex ) ; glDrawArrays ( GL_TRIANGLES , 0 , 6 ) ; glActiveTexture ( GL_TEXTURE0 ) ; glBindTexture ( GL_TEXTURE_2D , 0 ) ; glBindBuffer ( GL_ARRAY_BUFFER , 0 ) ; glUseProgram ( 0 ) ; }
target:  Present the final image on the screen/viewport.