# Object Decompilation Example A fairly typical example of an NPC's object is `object_bg`. It is used by one actor: `ovl_En_Bom_Bowl_Man`. ## First pass: getting it to compile Running `tools/xmlcreate.py` gives ```xml $ python3 tools/xmlcreate.py src/overlays/actors/ovl_En_Bom_Bowl_Man/z_en_bom_bowl_man.c chuGirl Unknown type at offset 004110 Unknown type at offset 004910 Unknown type at offset 005110 ``` We have two issues here that need to be resolved: naming the animations and sorting out the unknown things. ### Animations You have three choices to work out what the animations are: - Read the code and look at them in the game. - Hylian Toolbox - The latest versions of Z64Utils The first of these is probably simplest if you know the game and the actor well. In this case, we know that she is dozing when you first enter, wakes up when you talk to her, then leans on the counter with both hands. We can thus name them accordingly. Hylian Toolbox is terrible, but good for quick-and-dirty things like finding out what a particular animation does without booting up the game. Z64Utils is way better than Hylian Toolbox, but still in development. ### Unknowns Looking in the actor, the unknowns are assigned to segment 8 using `SEGMENTED_TO_VIRTUAL`. This indicates textures. To find out what type they are, we can find the displaylist that uses them, and look at it in Z64Utils: if we look at the object in the object analyser, then find the right displaylist, it will not display correctly in the DList viewer, asking for a texture to put on 08000000. Giving it one of the textures, we discover that it is the head displaylist and the textures are eye textures. Hence we can name them `gChuGirlEyeOpen/Half/ClosedTex` (we equivocate on half-open/half-closed since many actors use the half texture for both opening and closing). From the code in the displaylist that loads it, we can also extract the texture's format, namely ```c 06002FD8: gsDPLoadTextureBlock(D_08000000, G_IM_FMT_RGBA, G_IM_SIZ_16b, 32, 32, 0, G_TX_NOMIRROR | G_TX_CLAMP, G_TX_NOMIRROR | G_TX_CLAMP, 5, 5, 0, 0), ``` So all three are `Format="rgb5a1" Width="32" Height="32"`. ```xml ``` Having got this far, we can now run ```bash ./extract_assets.py -s objects/object_bg ``` to extract the contents of the object into the new folder, change the spec to use our newly extracted assets: ```txt beginseg name "object_bg" romalign 0x1000 include "build/baserom/object_bg.o" endseg ``` to ```txt beginseg name "object_bg" romalign 0x1000 include "build/assets/objects/object_bg/object_bg.o" number 6 endseg ``` and wipe the `z_en_bom_bowl_man` section from `undefined_syms.txt`: ```txt // z_en_bom_bowl_man D_06006EB0 = 0x06006EB0; D_06000710 = 0x06000710; D_06000080 = 0x06000080; D_060072AC = 0x060072AC; ``` Now `make` should give OK. ## The displaylists For this step, we use Hylian Toolbox; if you have more than one skeleton in your actor, Hylian Toolbox will only show the first one. The others can be examined in the latest version of Z64Utils. Z64Utils can also give you a list of every displaylist in an object, be it just for cross-checking or to find extras. Opening the rom in Hylian Toolbox and looking at object_bg, we can note down the displaylist associated to each limb. In this case naming is easy: we just have to note down the limb each is attached to. We only need a name and offset, and we end up with: ```xml ``` Checking the C file, these are all of the displaylists in the actor, so we can move on. ## The rest of the textures This is the difficult bit: we have to work out what each texture in the extracted pile is actually used for. A lot of this can be done in Z64Utils, but sometimes it is necessary to check in-game, especially for the weirder-looking ones. You can edit a texture file and compile the rom (which shouldn't match any more if you did it successfully) to make it easier to find. ```xml ``` ## Final pass Therefore, we end up with the following: ```xml ``` This was an easier object to do, both because it's a fairly simple collection of stuff associated to a single actor, and because a lot of the typing was already known.