QfG5: RGD revisited

This was the last format I haven’t looked too deep at. But as I’m tying loose ends, I decided to revisit it and see what I can get out of it.

As expected, RGD defines the 3D data for the room. I have not figured out all the additional values stored there (and I’m not sure that I got proper regions marked either) but at least the basic understanding proved out to be correct.

So, here’s what I got:

Arcane Island background

Arcane Island RGD

As you can see (especially if you click on the picture to see it in full glory), it is a flat map for the room (or rather like in Doom and Doom 2, a 3D surface consisting of differently raised polygons, pity I haven’t figured out which property is responsible for the heights). Essentially each region consists of a set of edges of different types (I marked them with different colours, you should be able to spot the blue edges around the area and some green polygons around the walkway and columns outlines). There is also a special list of marked regions (yellow ones on the picture but I’m not so sure about that) that are supposed to be walkable and there are even two connectivity matrices for them (for the record, on this particular map there are about nine hundred regions in total and only fifteen are marked as walkable).

From what I saw in the code, this map is used in the game to translate mouse coordinates into destination region, plot path to it, check the enemy line of sight (and projectiles) and so on.

Fun thing is that the format is not compact as the others (as I described it before, it’s a mess of various lists and references to other lists and so on) and so some data is unread. In some cases it is merely 4-8 bytes of padding between different blocks, in other cases it’s way more. For example, in 251.RGD you can see a piece of text “ctile Only. Region 448 contains entry point(s)” plus some other words here and there.

And as I hinted in my previous posts, that’s about it. I intend to write the final post explaining my problems with 3D rendering and why I’m giving up on it. At least I learned a lot more about my favourite game and had some fun while doing it, so it is not time completely wasted.

2 Responses to “QfG5: RGD revisited”

  1. Just want you to know that I read all of these chronicles and greatly enjoy them!

  2. Kostya says:

    On the one hand it’s surprising that you read it, on the other hand you’re one of the top MobyGames contributors and have a mention at https://tuxnes.sourceforge.net/ so it’s not that far-fetched for your tastes 😉

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