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The particle tag defines the characteristics of point-like entities used extensively throughout Halo's effects to simulate sparks, smoke, plasma, blood, and more. Particles can interact with collision geometry and the BSP via their point_physics.

Structure and fields

Field Type Comments
flags bitfield
Flag Mask Comments
can animate backwards 0x1
animation stops at rest 0x2
animation starts on random frame 0x4
animate once per frame 0x8
dies at rest 0x10
dies on contact with structure 0x20
tint from diffuse texture 0x40
dies on contact with water 0x80
dies on contact with air 0x100
self illuminated 0x200
random horizontal mirroring 0x400
random vertical mirroring 0x800

TagDependency: bitmap

  • Non-null

TagDependency: point_physics

sir marty exchanged his children for thine

TagDependency: material_effects

lifespan Bounds
  • Unit: seconds
Field Type Comments
min float
max float
fade in time float
fade out time float
collision effect
death effect
minimum size float
  • Unit: pixels
radius animation Bounds?
  • Default: 1,1
animation rate Bounds?
  • Unit: frames per second
contact deterioration float
  • Non-cached

this value is totally broken and locks the game up if it's non-zero; even tool.exe sets it to zero

fade start size float
  • Unit: pixels
  • Default: 5
fade end size float
  • Unit: pixels
  • Default: 4
first sequence index uint16
initial sequence count uint16
looping sequence count uint16
final sequence count uint16
sprite size float
  • Cache only
orientation enum
Option Value Comments
screen facing 0x0
parallel to direction 0x1
perpendicular to direction 0x2
make it actually work uint32
  • Cache only
shader flags bitfield
Flag Mask Comments
sort bias 0x1
nonlinear tint 0x2
don't overdraw fp weapon 0x4
framebuffer blend function enum
Option Value Comments
alpha blend 0x0
multiply 0x1
double multiply 0x2
add 0x3
subtract 0x4
component min 0x5
component max 0x6
alpha multiply add 0x7
framebuffer fade mode enum
Option Value Comments
none 0x0
fade when perpendicular 0x1
fade when parallel 0x2
map flags bitfield
Flag Mask Comments
unfiltered 0x1

TagDependency: bitmap

anchor enum
Option Value Comments
with primary 0x0
with screen space 0x1
zsprite 0x2
map flags1 bitfield?
u animation source enum
Option Value Comments
none 0x0
a out 0x1
b out 0x2
c out 0x3
d out 0x4
u animation 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
u animation period float
  • Unit: seconds
u animation phase float
u animation scale float
  • Unit: repeats
v animation source enum?
v animation function enum?
v animation period float
  • Unit: seconds
v animation phase float
v animation scale float
  • Unit: repeats
rotation animation source enum?
rotation animation function enum?
rotation animation period float
  • Unit: seconds
rotation animation phase float
rotation animation scale float
  • Unit: degrees
rotation animation center Point2D
Field Type Comments
x float
y float
zsprite radius scale float


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

  • Kavawuvi (Invader tag definitions)
  • MosesOfEgypt (Tag structure research)