Add Quake II MD2 model format

[jdjakub]

I've been working with this format recently and saw it was missing, so I plugged the gap! I've followed the syle guide as far as I can tell, though being new to Kaitai I don't know what I should do with the overfull conditional expression lines.

You can find examples as tris.md2 under http://tastyspleen.net/~quake2/baseq2/players/. A nice, simple example is crate/tris.md2 which is just standard box geometry repeated across all frames.

[generalmimon]

Overall, this PR is of pretty good quality.

[jdjakub]

I added this section, formatted the table like this from the POV of someone reading a text file. However, now I think about it, will the doc section be rendered as Markdown in a web page? In which case, I should make this a Markdown table?

[jdjakub]

I've made this a Markdown table so it should display correctly. I think this PR is ready to merge.

[generalmimon]

@jdjakub:

will the doc section be rendered as Markdown in a web page?

Yes. The top-level doc key is rendered at https://formats.kaitai.io/ as the format description.

I've made this a Markdown table so it should display correctly.

Unfortunately, the Markdown dialect we use is CommonMark, which doesn't provide markup for tables. So you could use either use HTML syntax (<table> etc. - it would probably lose the readability a bit), or you may insert a plaintext code block ``` with an ASCII-formatted table.

ASCII table is fine, if you ask me.

[jdjakub]

I've now expanded the table as a preformatted block. Do you have any thoughts on my Sep 21 comment below beginning "I have added this machine-readable version of part of the animation table..."?

[jdjakub]

I have added this machine-readable version of part of the animation table. I would also like to include machine-readable data for how many frames each anim has, but I can't see how to do this in Kaitai. For example, the three pain anims all have 4 frames, which would clash if I tried to use another enum for this purpose. Is there any way to include constant key-value definitions where several keys might share the same value?

[generalmimon]

@jdjakub:

For example, the three pain anims all have 4 frames, which would clash if I tried to use another enum for this purpose.

Yes, an enum in Kaitai Struct is a strictly bidirectional mapping (one-to-one correspondence).

Is there any way to include constant key-value definitions where several keys might share the same value?

You can use value instances to define constants:

instances:
  my_const:
    value: 4

Technically you can also declare arrays there (though I'm not sure whether it makes sense here):

instances:
  my_array:
    value: |
      [2, 3, 5, 7, 11, 13]

Another option (but it depends on what you mean by machine-readable) may be to add a custom YAML key somewhere. KS compiler ignores any properties starting with a dash - (see https://doc.kaitai.io/user_guide.html#orig-id), so this can be used to add arbitrary metadata. But these keys won't be provided in generated parsers.

[jdjakub]

Thanks. I have replaced the enum with three value instances and updated the doc to refer to them. If it's OK then please go ahead and merge, I want to be able to look it up on the website :)

[jdjakub]

I've incorporated your suggested changes.

[jdjakub]

Thanks for your detailed dive into all the issues. I've incorporated your changes. Back to you :)

[jdjakub]

Hello! I think this is mergeable now.

[generalmimon]

@jdjakub Looks good to me, thanks for your hard work on this spec and the reminder!