A Story

If you’ve used GameMaker for a bit, you might know what’s wrong with this.

instance_create_depth(omod_instance, 0, 0, 10)

The arguments are in the wrong order, but instead of providing a helpful error message, GameMaker accepts the arguments and keeps running. The reason why GameMaker doesn’t reject this function call is because omod_instance is actually just a number. This is what GameMaker actually sees:

instance_create_depth(329, 0, 0, 10)

“Pointers”

If you’ve taken a low-level programming course or come from other game engines, then this probably isn’t too unexpected. Because of boring performance reasons, it’s better to use a single number than an entire string, at the cost of making things slightly more difficult.

Basically everything the game tracks is secretly just a number. This includes Game Objects, Instances, Sprites, Rooms, audio assets, shaders, constants (ie ev_create, vk_home, etc ), some GML language keywords (self, all, true, etc), functions, data structures (buffers, ds_maps, etc), and probably more I haven’t run into yet.

Here’s a few common keywords and their internal numbers.

For most use cases, this information is irrelevant. However, if you’re using json_stringify for serialization or debugging purposes, you should use json_encode with GML data structures.

Undertale Mod Tool

When using Undertale Mod Tool, eventually you’ll run into code that looks like this.

// gml_Object_oplayer_Create_0
...
  sprite_dead = 595
  sprite_hit = 1369
  hair_start_col = 3026478
  hair_end_col = 6707256
  hair_number = 3
  hair_size = 2.5
  hair_alt = -1
...

Despite all seven variables being initialized to numbers, their actual purpose varies dramatically. The first two, sprite_dead and sprite_hit, are referencing Sprite indexes for splayer_maya_dead and splayer_maya_hit respectively. hair_start_col and hair_end_col are hex code colors, 2E 2E 2E and 66 58 38 in RGB. hair_alt is -1 so it evaluates as false for conditional statements, but is normally an array. hair_number and hair_size are the only two “normal” numbers here.

When using Undertale Mod Tool, you can right click on one of these weird numbers and get a list of possible assets it could be. If you’ve exported the code or are looking for references to a Game Object or Sprite, you might want a list of every internal identifier.

Identifier Dump Mod

The key technology here are the _get_name functions, which take an identifier and return the name of the asset. Additionally, these identifiers are not stable. If possible, you should use the actual names of the asset, or find the index at runtime.

# controller

## create

```sp
global.ripper = {}
global.ripper.type = 2
global.ripper.saved_index = 0
global.ripper.max = 100
```

## step

```sp
let log = file_text_open_append("asset_list.txt")

let i = 0
while i < global.ripper.max {
  let name
  let next
  let exists = false
  match global.ripper.type {
    case 0 {
      name = sprite_get_name(global.ripper.saved_index)
      exists = sprite_exists(global.ripper.saved_index)
      next = "room"
    }
    case 1 {
      name = room_get_name(global.ripper.saved_index)
      exists = room_exists(global.ripper.saved_index)
      next = "object"
    }
    case 2 {
      name = object_get_name(global.ripper.saved_index)
      exists = object_exists(global.ripper.saved_index)
      next = "END"
    }
    case 4 {
      file_text_close(log)
      !"Done"
    }
  }

  if !exists {
    file_text_write_string(log, next + "\n")
    global.ripper.saved_index = -1
    global.ripper.type += 1
  } else {
    file_text_write_string(log, string(global.ripper.saved_index) + "\t:" + name + "\n")
  }
  i += 1
  global.ripper.saved_index += 1
}

file_text_close(log)
```