object (abstract tag)

Edit

Objects are a high-level abstract tag, meaning they serve as a base for many other tag types but cannot be directly created themselves. Generally, they are "things" with a position in the world but are distinct from the "level" itself. Some examples include elevators, trees, warthogs, and the player.

Some capabilities available to objects (though not used by every subtype) are:

Be rendered with a model
Have physics and be collideable
Cast shadows using lightmap data
Have attachments like particles, sounds, and lights
Be attached to each other (e.g. pelicans carrying warthogs)

Shadows

For most dynamic objects, Halo uses shadow mapping with their render model, unless the object's "does not cast shadow" flag is true. However, with scenery, shadows are baked into the lightmap using the object's collision geometry instead, regardless of the "does not cast shadow" flag.

Structure and fields

Field Type Comments

object type

enum (little endian^?)

Internal to the tag and may be hidden in tools.
This field's value may change at build time or have precision errors. It should not be used for exact comparisons between tag data.

Option	Value	Comments
biped	`0x0`
vehicle	`0x1`
weapon	`0x2`
equipment	`0x3`
garbage	`0x4`
projectile	`0x5`
scenery	`0x6`
device machine	`0x7`
device control	`0x8`
device light fixture	`0x9`
placeholder	`0xa`
sound scenery	`0xb`

flags bitfield(16)

Flag	Mask	Comments
does not cast shadow	`0x1`
transparent self occlusion	`0x2`	Causes the transparent shaders in this object to occlude each other rather than be visible through each other. The scene behind the object is still visible. Warning: enabling this flag while the object uses transparent shaders with extra layers causes Sapien to crash when near the object, though the same object will work ingame.
brighter than it should be	`0x4`	Slightly brightens the object, making it easier to see in the dark for gameplay purposes. Often used for small items like weapons, powerups, and ammunition.
not a pathfinding obstacle	`0x8`

bounding radius

f32 (world units)

A radius which encompasses the object, used by the engine for a variety of purposes. If the bounding radius is too small, shadows will be cut off.

bounding offset

Point3D (3)

x: f32
y: f32
z: f32

origin offset

Point3D (3)

x: f32
y: f32
z: f32

acceleration scale

f32

Affects how much objects are moved by explosions. A value of 0 means the object remains fixed (like the multiplayer flag weapon). This value works for items, bipeds, and vehicles (vehicles must also have a physics tag set), but not devices and scenery. See also the instantaneous acceleration field of damage_effect for the source of explosion acceleration.

scales change colors

u32 (little endian^?)

Only set when the tag is compiled into a map cache.

model

Reference^?

animation graph

Reference^?: model_animations

pad(40)

collision model

Reference^?: model_collision_geometry

physics

Reference^?: physics

modifier shader

Reference^?: shader

A modifier shader automatically uses the entire object and its attachments as a geometry source when rendering. It is used for energy shields which need to encompass both the object's own gbxmodel, but also any held weapons in the case of bipeds.

creation effect

Reference^?: effect

pad(84)

render bounding radius f32 (world units)

a in enum

Option	Value	Comments
none	`0x0`
body vitality	`0x1`
shield vitality	`0x2`
recent body damage	`0x3`
recent shield damage	`0x4`
random constant	`0x5`
umbrella shield vitality	`0x6`
shield stun	`0x7`
recent umbrella shield vitality	`0x8`
umbrella shield stun	`0x9`
region	`0xa`
region 1	`0xb`
region 2	`0xc`
region 3	`0xd`
region 4	`0xe`
region 5	`0xf`
region 6	`0x10`
region 7	`0x11`
alive	`0x12`
compass	`0x13`

b in enum

Option	Value	Comments
none	`0x0`
body vitality	`0x1`
shield vitality	`0x2`
recent body damage	`0x3`
recent shield damage	`0x4`
random constant	`0x5`
umbrella shield vitality	`0x6`
shield stun	`0x7`
recent umbrella shield vitality	`0x8`
umbrella shield stun	`0x9`
region	`0xa`
region 1	`0xb`
region 2	`0xc`
region 3	`0xd`
region 4	`0xe`
region 5	`0xf`
region 6	`0x10`
region 7	`0x11`
alive	`0x12`
compass	`0x13`

c in enum

Option	Value	Comments
none	`0x0`
body vitality	`0x1`
shield vitality	`0x2`
recent body damage	`0x3`
recent shield damage	`0x4`
random constant	`0x5`
umbrella shield vitality	`0x6`
shield stun	`0x7`
recent umbrella shield vitality	`0x8`
umbrella shield stun	`0x9`
region	`0xa`
region 1	`0xb`
region 2	`0xc`
region 3	`0xd`
region 4	`0xe`
region 5	`0xf`
region 6	`0x10`
region 7	`0x11`
alive	`0x12`
compass	`0x13`

d in enum

Option	Value	Comments
none	`0x0`
body vitality	`0x1`
shield vitality	`0x2`
recent body damage	`0x3`
recent shield damage	`0x4`
random constant	`0x5`
umbrella shield vitality	`0x6`
shield stun	`0x7`
recent umbrella shield vitality	`0x8`
umbrella shield stun	`0x9`
region	`0xa`
region 1	`0xb`
region 2	`0xc`
region 3	`0xd`
region 4	`0xe`
region 5	`0xf`
region 6	`0x10`
region 7	`0x11`
alive	`0x12`
compass	`0x13`

pad(44)

hud text message index Index: u16

forced shader permutation index Index: u16

attachments Block^?

Field Type Comments

type

Reference^? (6)

marker char[32]

primary scale enum

Option	Value	Comments
none	`0x0`
a out	`0x1`
b out	`0x2`
c out	`0x3`
d out	`0x4`

secondary scale enum

Option	Value	Comments
none	`0x0`
a out	`0x1`
b out	`0x2`
c out	`0x3`
d out	`0x4`

change color enum

Option	Value	Comments
none	`0x0`
a	`0x1`
b	`0x2`
c	`0x3`
d	`0x4`

pad(2)

pad(16)

widgets

Block^?

Similar to attachments, but without function-driven properties and a marker location. Some examples include the Warthog antenna and projectile light_volumes. There is a known PC renderer issue where projectile widgets (but not attachments) are improperly offset in mirrored reflections like the floor of the control room.

Field	Type	Comments
reference	`Reference^?` (5) antenna glow light_volume lightning flag
	`pad(16)`

functions Block^?

Field Type Comments

flags bitfield(32)

Flag	Mask	Comments
invert	`0x1`
additive	`0x2`
always active	`0x4`

period

f32 (seconds)

Default value: 1

scale period by enum

Option	Value	Comments
none	`0x0`
a in	`0x1`
b in	`0x2`
c in	`0x3`
d in	`0x4`
a out	`0x5`
b out	`0x6`
c out	`0x7`
d out	`0x8`

function enum

Option	Value	Comments
one	`0x0`
zero	`0x1`
cosine	`0x2`
cosine variable period	`0x3`
diagonal wave	`0x4`
diagonal wave variable period	`0x5`
slide	`0x6`
slide variable period	`0x7`
noise	`0x8`
jitter	`0x9`
wander	`0xa`
spark	`0xb`

scale function by enum

Option	Value	Comments
none	`0x0`
a in	`0x1`
b in	`0x2`
c in	`0x3`
d in	`0x4`
a out	`0x5`
b out	`0x6`
c out	`0x7`
d out	`0x8`

wobble function enum

Option	Value	Comments
one	`0x0`
zero	`0x1`
cosine	`0x2`
cosine variable period	`0x3`
diagonal wave	`0x4`
diagonal wave variable period	`0x5`
slide	`0x6`
slide variable period	`0x7`
noise	`0x8`
jitter	`0x9`
wander	`0xa`
spark	`0xb`

wobble period f32 (seconds)

wobble magnitude f32 (percent)

square wave threshold Fraction: f32

step count u16

map to enum

Option	Value	Comments
linear	`0x0`
early	`0x1`
very early	`0x2`
late	`0x3`
very late	`0x4`
cosine	`0x5`

sawtooth count u16

add enum

Option	Value	Comments
none	`0x0`
a in	`0x1`
b in	`0x2`
c in	`0x3`
d in	`0x4`
a out	`0x5`
b out	`0x6`
c out	`0x7`
d out	`0x8`

scale result by enum

Option	Value	Comments
none	`0x0`
a in	`0x1`
b in	`0x2`
c in	`0x3`
d in	`0x4`
a out	`0x5`
b out	`0x6`
c out	`0x7`
d out	`0x8`

bounds mode enum

Option	Value	Comments
clip	`0x0`
clip and normalize	`0x1`
scale to fit	`0x2`

bounds

Fraction: f32 (min & max)

Default value: 0,1

pad(4)

pad(2)

turn off with i16

scale by f32

pad(252)

inverse bounds

f32 (little endian^?)

Only set when the tag is compiled into a map cache.

unknown float 2

f32 (little endian^?)

Only set when the tag is compiled into a map cache.

inverse step

f32 (little endian^?)

Only set when the tag is compiled into a map cache.

inverse period

f32 (little endian^?)

Only set when the tag is compiled into a map cache.

usage char[32]

change colors Block^?

Field Type Comments

darken by enum

Option	Value	Comments
none	`0x0`
a in	`0x1`
b in	`0x2`
c in	`0x3`
d in	`0x4`
a out	`0x5`
b out	`0x6`
c out	`0x7`
d out	`0x8`

scale by enum

Option	Value	Comments
none	`0x0`
a in	`0x1`
b in	`0x2`
c in	`0x3`
d in	`0x4`
a out	`0x5`
b out	`0x6`
c out	`0x7`
d out	`0x8`

flags bitfield(32)

Flag	Mask	Comments
blend in hsv	`0x1`
more colors	`0x2`

color lower bound

ColorRGB (3)

red: f32
green: f32
blue: f32

color upper bound

ColorRGB (3)

red: f32
green: f32
blue: f32

permutations Block^?

Field	Type	Comments
weight	`f32`	Default value: 1
color lower bound	`ColorRGB` (3) red: `f32` green: `f32` blue: `f32`
color upper bound	`ColorRGB` (3) red: `f32` green: `f32` blue: `f32`

predicted resources Block^?

PredictedResource

This information was partially generated using Invader tag definitions.

Acknowledgements

Thanks to the following individuals for their research or contributions to this topic:

Jakey (Explaining modifier shaders.)
Kavawuvi (Invader tag definitions)
MosesOfEgypt (Tag structure research)
Satania (Explaining acceleration scale.)