Apex Legends Water Bodies system

[snake-biscuits]

Splitting off from:

• Unknown Apex Legends Lumps #102

Lumps

• WATER_BODIES
• WATER_BODY_CENTERS
• WATER_BODY_INDICES
• WATER_BODY_VERTICES
• WAVE_DATA

Connections

WaterBody -> WaterBodyIndex -> WaterBodyVertex -> WaveData
         \-> WaterBodyCenter

Unknowns

• How do WaterBodies index WaterBodyVertices2? WaterBodyCenters are tile centers
• WaterBody.unknown_1 (approximate mesh center?)
• WaterBody.unknown_2 .rpak asset hash
• WaterBodyVertex.unknown_index_1 & 2 colour, either white or blue; 1 colour per tile
• What precisely do WaterBody.rpak_hashes index? targetname_hash indexes an entity
  • Are all the indexed assets in mapname.rpak, or some other mounted .rpak?
• Are WaterBodyCenters used to generate a deformable mesh of the ocean?
• Didn't Respawn make a blog post about this system at some point? or a tweet?

[snake-biscuits]

WaterBody

origin

Roughly matches origin of paired entity

height

Sea level
Always matches bounds.mins.z & bounds.maxs.z

bounds

mins & maxs (vec3)
Snapped to a node_size grid

Storm Point mu2

Indices into other lumps

6 ints, looks like first_X, num_X pairs
Haven't found a lump of a length matching the last first + num
Presumably indexes Indices & Vertices

1st pair indexes WaterBodyCenters
2nd pair indexes WaterBodyVertices
3rd pair indexes WaterBodyIndices

Storm Point mu2

first 1	num 1	first 2	first 3	num 2	num 3
0	246	0	0	984	1476
246	244	984	1476	976	1464
490	216	1960	2940	864	1296
706	168	2824	4236	672	1008
874	255	3496	5244	1020	1530
1129	235	4516	6774	940	1410
1364	124	5456	8184	496	744
1488	191	5952	8928	764	1146

targetname_hash

uint64_t
@r-ex connected this to materials/world/ocean_water
Hashed the same way as .rpak assets, but actually for entity targetnames

uv_scale

Small float representing the amount to increment a uv tile across the 1K WaveData texture
1024 * step_size represents how many pixels across a tile is (might also be some border amount to avoid bleed)

node_scale

Always 1024.0, the x & y dimension of a tile in the mesh

[snake-biscuits]

WaveData

1024x1024 RGBA 32-bit texture
Only the Blue & Green channels of the texture have data, the rest are blank

Extraction

>>> from PIL import Image
>>> with open("maps/mp_rr_tropic_island_mu2.bsp.0030.bsp_lump", "rb") as raw_file:
...     Image.frombytes("RGBA", (1024, 1024), raw_file.read(), "raw").save("storm_point.wave_data.raw.tga")

Alpha channel will need to be inverted / disabled, otherwise the image will appear invisible
If you save as .png transparent pixels' colour will be deleted.

Raw Tilesheets

Storm Point

Habitat

[snake-biscuits]

Managed to use these textures as tilesets in Aseprite
Could piece together some patterns, was kinda painful tho

No idea what the gradient is about yet

I presume these tiles get indexed to create textures somewhere

Indices likely start at the bottom left corner
Building a row from tiles as you increment upwards can make some legible shapes
However it quickly falls apart, some tiles might be getting rotated & reused

[snake-biscuits]

WaterBodyVertex

class WaterBodyVertex(base.Struct):  # LUMP 46 (002E)
    position: vector.vec3
    uv: vector.vec2
    colour: colour.RGBA32
    _format = "5f4b"

colour is always 100% white or 100% blue
Might act as a mask in the shader

[snake-biscuits]

Made a quick change to the .water_body_mesh method to fake vertex colour in .obj w/ normals

Looks like vertex colours apply to the whole tile

[snake-biscuits]

WaterBodyIndex

uint16_t
Lump length doesn't seem to line up with any of the other data
Fairly small max, smaller than WaterBodyVertex lump sizes anyway

Definitely has patterns to make triangle-based meshes

[snake-biscuits]

.water_body_mesh

>>> import bsp_tool
>>> bsp = bsp_tool.load_bsp("E:/Mod/ApexLegends/season19/1feb24/maps/mp_rr_tropic_island_mu2.bsp")
>>> from bsp_tool.utils import geometry
>>> model = geometry.Model([bsp.external.water_body_mesh(i) for i in range(4)])
>>> from bsp_tool.extensions.geometry import obj
>>> obj.Obj([model]).save_as("habitat_water_bodies.obj")

[snake-biscuits]

Now .water_body_model, since we have origin
Also trying to get material from the entity
Not matching the entity to the WaterBody atm tho, just assuming they all use the same material

[snake-biscuits]

water_body entity

>>> import bsp_tool
>>> bsp = bsp_tool.load_bsp("E:/Mod/ApexLegends/season19/1feb24/maps/mp_rr_tropic_island_mu2.bsp")
>>> bsp.external.ENTITIES.search(classname="water_body")
[{'surfpropindex': '14',
  'solid': '0',
  'nodesize': '1024',
  'model': 'mdl/dev/editor_ref.rmdl',
  'origin': '-42315.900000000001 16249.9 66',
  'targetname': 'zone_01_water',
  'material': 'world/OceanWater/tropics_ocean_water_01_mu2',
  'height': '-8',
  'classname': 'water_body'},
 ...]  # 8 entries, 1 per WaterBody

@r-ex found the code which looks up this entity
Turns out what we thought was an rpak asset hash is actually the targetname

Can use the entity keys to determine struct member names now

[snake-biscuits]

It's a pretty safe assumption that the entities are in the same order as WaterBodies

>>> [e["origin"] for e in bsp.external.ENTITIES.search(classname="water_body")]
['-42315.900000000001 16249.9 66',
 '-21976.700000000001 38176.300000000003 0',
 '-43444.400000000001 -17589.200000000001 0',
 '-17726.599999999999 -30762.099999999999 0',
 '-6005.6000000000004 -51356.300000000003 0',
 '29753.099999999999 -34200.400000000001 0',
 '24443.200000000001 -15226.200000000001 0',
 '46764.5 -9304.1900000000005 0']

>>> [wb.center for wb in bsp.external.WATER_BODIES]
[vec2(-42315.8984375, 16249.900390625),
 vec2(-21976.69921875, 38176.30078125),
 vec2(-43444.3984375, -17589.19921875),
 vec2(-17726.599609375, -30762.099609375),
 vec2(-6005.60009765625, -51356.30078125),
 vec2(29753.099609375, -34200.3984375),
 vec2(24443.19921875, -15226.2001953125),
 vec2(46764.5, -9304.1904296875)]

[snake-biscuits]

Moving this discussion to the completed category
We still don't 100% understand how the Water Bodies system is rendered, but we understand the structs