I have an openGL program that works if I use vertex arrays to store the geometry data, but if I convert it to use an openGL vertex buffer object then nothing is drawn. Has anyone got vertex buffer objects to work with MacRuby? I am using 0.8 on 10.6.4 (In OpenGL a vertex buffer object just holds geometry but on the graphics card so for large amounts of geometry will be significantly faster than a vertex array where the geometry is held in the client's memory and copied to the graphics card every time it is drawn). The code is: @vbo_buffer = Pointer.new('f', 1000) ... # initialise with vertex data (BYTES_IN_BUFFER set up with the size of the vertex data) # Get a buffer object id cubeVBO = Pointer.new_with_type('I', 1) glGenBuffers(1, cubeVBO) @cubeVBO = cubeVBO[0] glBindBuffer(GL_ARRAY_BUFFER, @cubeVBO) # The vertex buffer object can be initialised in several ways case vbo_method when :writeOnAllocate # This call will allocate the vertex buffer object and initialise it from @vbo_buffer glBufferData(GL_ARRAY_BUFFER, BYTES_IN_BUFFER, @vbo_buffer, GL_STATIC_DRAW) when :writeAfterAllocate nullPtr = Pointer.new("^I") # This call will allocate the vertex buffer object but not initialise it. glBufferData(GL_ARRAY_BUFFER, BYTES_IN_BUFFER, nullPtr, GL_STATIC_DRAW) # Now initialise it. glBufferSubData(GL_ARRAY_BUFFER, 0, BYTES_IN_BUFFER, @vbo_buffer) when :mapAfterAllocate nullPtr = Pointer.new("^I") # This call will allocate the vertex buffer object but not initialise it. glBufferData(GL_ARRAY_BUFFER, BYTES_IN_BUFFER, nullPtr, GL_STATIC_DRAW) # Get a pointer to the allocated buffer and copy the data over manually. buffer = glMapBuffer(GL_ARRAY_BUFFER, GL_READ_WRITE).cast!('f') (BYTES_IN_BUFFER / 4).times {|i| buffer[i] = @vbo_buffer[i]} # copy as floats glUnmapBuffer(GL_ARRAY_BUFFER) end Finally to draw the vertex buffer object glBindBuffer(GL_ARRAY_BUFFER, @cubeVBO) glEnableClientState(GL_VERTEX_ARRAY) v = Pointer.new("^c") # gives us a null pointer - need to pass in 0 in next call glVertexPointer(3, GL_FLOAT, v) glColor3f(1.0, 0.0, 0.0) glDrawArrays(GL_QUADS, 0, 24) # 0 = start offset, 24 = number of vertices None of the three methods to load the vertex buffer object make a difference. The other problem I will have is the colour data is interleaved in with the vertex data so ideally I need to call: glVertexPointer(3, GL_FLOAT, 12) but this function needs to take a void* pointer so how do I create a pointer with a value? Dave.