Question

I’m working with OpenGL, and using buffers to store vertex data in video memory. For effiency / convenience, I’m allocating big chunks of video memory, and then reserving chunks as I need them. There are three data structures I’m using:

• The buffer itself.
• A “chunk” of the buffer – a contiguous block of memory within thebuffer.
• A “skippy chunk” within a regular chunk. OpenGL lets you interlace your vertex attributes, and these “skippy chunks” let you describe how different attributes are woven together within a chunk / buffer.

Now I reckon that “Buffer” is a good name for that first data structure, but what are the other two called? I assume there’s a technical term, but I don’t know it, and don’t know how to find it…

And here’s an example memory layout, to back up my sketchy description (this buffer has three types of attributes: colors, vertices, and normals):

+--+--+--+--+--+--+--+--+--+--+--+
|c1|c2|c3|c4|c5|v1|n1|v2|n2|v3|n3|
+--+--+--+--+--+--+--+--+--+--+--+
|------------Buffer--------------| <- Buffer Class
|----chunk1----|------chunk2-----| <- "Chunk" classes
               |--|  |--|  |--|    <- "Skippy Chunk" class (vertices)
                  |--|  |--|  |--| <- "Skippy Chunk" class (normals)

Thanks in advance!

Answer 1

The part with your “skippy chunks” resembles interleaved arrays.
It is quite common to mix such data (vertices, texture coordinates, normals, colors, …) in a chunk of linear memory (“buffer”) and access it using base addresses, offsets, and strides.