object (abstract tag)

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 and lighting

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.

Objects receive a few parameters from the environment as inputs to their lighting model. These include up to two distant light sources (direction and colour), ambient light, reflection tint, shadow direction, and shadow colour. Lighting is calculated when objects are created and also when dynamic objects move. To do this the game casts a ray straight down to a BSP ground point up to 10 world units away to determine its lighting and can result in a few scenarios:

If a ground point is found within 10 units, that surface's lightmap colour is used to light the object. This is why even an object in direct sunlight can appear dark when it is sampling the ground beneath it. The shadow vector is an interpolation of lightmap vertex normals. In this scenario you will see a coloured vector drawn over objects with debug_object_lights 1.
If a ground point is not found and the BSP tag has a non-zero red value for default ambient color field, BSP default lighting fields will apply.
Otherwise the object receives hard-coded white light from the +x +y direction and casts shadows straight down.

You can test the latter two scenarios by setting debug_collision_skip_vectors 1 to make the ray cast always fail. Scenery which are outside the BSP will also fail to get a ground point and therefore receive default lighting.

	Function/global	Type
	`(debug_objects [boolean])` When enabled, toggles if debug information is visible on objects (such as bounding sphere and collision models). Individual debug features can be toggled with the `debug_objects_*` commands.	Global
	`(debug_objects_biped_autoaim_pills [boolean])` When `debug_objects` is enabled, displays biped autoaim pills in red.	Global
	`(debug_objects_biped_physics_pills [boolean])` When `debug_objects` is enabled, displays biped physics pills in white.	Global
	`(debug_objects_bounding_spheres [boolean])` When `debug_objects` is enabled, displays yellow spheres for object bounding radius. The sphere will be black when the object is inactive. This setting defaults to `true` in H1CE Sapien but not H1A Sapien.	Global
	`(debug_objects_collision_models [boolean])` When `debug_objects` is enabled, displays green meshes for object collision models. This setting defaults to `true` in H1CE Sapien but not H1A Sapien.	Global
	`(debug_objects_names [boolean])` Toggles the display of object names, for named objects. The names are shown in purple.	Global
	`(debug_objects_pathfinding_spheres [boolean])` When `debug_objects` is enabled, displays object pathfinding spheres in blue.	Global
	`(debug_objects_physics)` When `debug_objects` is enabled, displays physics mass points as white spheres.	Global
	`(debug_objects_position_velocity)` When `debug_objects` is enabled, displays red, green, and blue object-space reference axes and a yellow velocity vector on each object.	Global
	`(debug_objects_root_node)` When `debug_objects` is enabled, displays red, green, and blue object-space reference axes and orange text including object ID, class, and tag name on each object. Defaults to `true` in H1A.	Global
	`(debug_objects_unit_seats)` When `debug_objects` is enabled, displays blue markers at unit seat locations, red markers at their entry points, and a yellow marker at the object origin.	Global
	`(debug_objects_unit_vectors)` When `debug_objects` is enabled, displays white and red vectors on objects. Their meaning is unknown.	Global
	`(debug_object_lights)` Shows the incoming light colour and vector for all objects which results from sampling lightmap data at the ground point beneath the object. This data is used to shade the object and cast its shadow.	Global
	`(object_light_ambient_base)` Sets the amount of ambient light all objects receive. Note that this only affects moving objects when their lighting updates, so you will not see any change on scenery. Setting this to `1` makes objects fullbright. Defaults to `0.03`.	Global
	`(object_light_ambient_scale)` Scales ambient light from the lightmap. Defaults to `0.4`.	Global
	`(object_light_interpolate)` Toggles if object lighting transitions smoothly when the object moves between different ground point surfaces or default lighting.	Global
	`(object_light_secondary_scale)` Scales secondary light on objects, but doesn't apply to default lighting. Defaults to `1`.	Global

Structure and fields

Field Type Comments

object type

enum

Volatile
Hidden

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

Flag	Mask	Comments
does not cast shadow	`0x1`	Prevents this object from casting dynamic shadows. Does not apply to scenery, which cast shadows in lightmaps using their collision model.
transparent self occlusion	`0x2`
brighter than it should be	`0x4`	Causes the object to have extra ambient lighting so it's easier to see in dark spaces. This is used for items which are important to gameplay like weapons and powerups.
not a pathfinding obstacle	`0x8`

bounding radius

float

Unit: world units

The bounding radius sets the approximate maximum size of the object and is used for a variety of optimizations by the game:

Culling objects for rendering which are not partially on screen.
Setting the shadow map size for dynamic object shadows.
Selecting an appropriate LOD.
Skipping collision checks.

The radius should contain this object completely, but not be too large. Setting it too high will cause the object to draw unccessarily when off-screen, but setting it too low will cause the object to have clipped shadows, pop in and out of visibility at the edges of the screen, and have inconsistent collision with other objects.

The bounding radius can be visualized in Sapien or Standalone using debug_objects_bounding_spheres.

bounding offset Point3D

Field	Type	Comments
x	`float`
y	`float`
z	`float`

origin offset Point3D^?

acceleration scale

float

Min: 0

scales change colors

uint32

Cache only

model

TagDependency

animation graph TagDependency: model_animations

collision model TagDependency: model_collision_geometry

physics TagDependency: physics

modifier shader TagDependency: shader

creation effect TagDependency: effect

render bounding radius

float

Unit: 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^?

c in enum^?

d in enum^?

hud text message index uint16

forced shader permutation index uint16

attachments

Block

HEK max count: 8

Field Type Comments

type

TagDependency (6)

marker TagString

primary scale enum

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

secondary scale enum^?

change color enum

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

widgets

Block

HEK max count: 4

Field	Type	Comments
reference	`TagDependency` (5) antenna glow light_volume lightning flag

functions

Block

HEK max count: 4
Max: 4

Processed during compile

Field Type Comments

flags bitfield

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

period

float

Unit: seconds
Default: 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^?

wobble function enum^?

wobble period

float

Unit: seconds

wobble magnitude

float

Unit: percent

square wave threshold float

step count uint16

map to enum

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

sawtooth count uint16

add enum^?

scale result by enum^?

bounds mode enum

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

bounds

Bounds

Default: 0,1

Field	Type	Comments
min	`float`
max	`float`

turn off with int16

scale by float

inverse bounds

float

Cache only

inverse sawtooth

float

Cache only

inverse step

float

Cache only

inverse period

float

Cache only

usage TagString

change colors

Block

HEK max count: 4
Max: 4

Processed during compile

Field Type Comments

darken by enum^?

scale by enum^?

flags bitfield

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

color lower bound ColorRGB

color upper bound ColorRGB

permutations

Block

HEK max count: 8

Field	Type	Comments
weight	`float`	Default: 1
color lower bound	`ColorRGB`
color upper bound	`ColorRGB`

predicted resources

Block

HEK max count: 1024
Cache only

Field Type Comments

type enum

Option	Value	Comments
bitmap	`0x0`
sound	`0x1`

resource index uint16

tag uint32

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.)

object (abstract tag)

Shadows and lighting

Related HaloScript

Structure and fields

Acknowledgements