Particle Script

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Morphball render.png This file format is almost completely documented
Elements beyond MP1 need to be discovered and documented

Retro games feature a uniform, fixed-function Particle Script system for describing various geometrical effects and weapon systems. The PAK archives contain binary resources using FourCCs to build a key-value dictionary. These codes correspond to application-specific parameters controlling the system in question.

The scripts use a dataflow paradigm built around value-generating element classes of the following types:

  • Int
  • Real (float)
  • Vector (3-component float)
  • Mod Vector (3-component float)
    • Local velocity vector in/out
    • Local position vector in/out
  • Color (4-component float, internally converted to RGBA8)
  • UV (TXTR reference and UV coordinate source)
  • Emitter
    • Initial local position vector (3-component float)
    • Initial local velocity vector (3-component float)

The system features several subclasses that output generated values through GetValue as a function of the current frame index. These implementations may recursively accept input from other elements, permitting effect designs of scalable complexity.

File Layout

All effect script file formats are read linearly to populate a description tree of element nodes, serving as a template to build an arbitrary number of generator instances:

  • Script Magic FourCC (see table below)
  • Parameters
    • Key FourCC
    • Value Parameter(s) (one of:)
      • NONE: null value (equivalent to not specifying the key at all)
      • Element FourCC (see below)
        • Child Elements (count/types according to parent)
  • _END

Script Types

Type Magic Purpose
PART GPSM Particle element generator
SWHC SWSH Swoosh generator
ELSC ELSM Electric generator
DPSC DPSM Decal generator
WPSC WPSM Projectile weapon configuration
CRSC CRSM Projectile collision response configuration

Elements

Many of the animated qualities in particle scripts are achieved with dynamic elements. These elements provide I/O interfaces and internally process numeric data that passes through. They may also gather data from other sources within the particle system's state.

Int Elements

FourCC Parameters Description Notes MP1 MP2 MP3 DKCR DKCTF
ADD_ (IntElement a, IntElement b) Add Returns a + b
CHAN (IntElement a, IntElement b, IntElement thresholdFrame) Time Chain Returns a when current frame index is less-than thresholdFrame, otherwise b
CLMP (IntElement min, IntElement max, IntElement val) Clamp Returns val clamped between min and max
CNST (s32 value) Constant Returns value on every call
DETH (IntElement passthrough, IntElement thresholdFrame) Death Always returns passthrough, and signals out-of-band to cease updating the system when the current frame index exceeds thresholdFrame
GAPC () Get Active Particle Count Accesses the current count of particles in the system
GEMT () Get Emitter Time Accesses the current frame count for the current particle system
GTCP () Get Cumulative Particle Count Accesses the total number of particles created over the particle system's lifetime (including those that have died)
ILPT (IntElement percent) Lifetime Percent Queries the frame index at percent/100.0 into the lifetime of the particle instance
IMPL (IntElement val) Impulse Returns val ONLY at frame index 0, then returns 0 for subsequent frames
IRND (IntElement a, IntElement b) Initial Random Rolls a random value between a and b on frame index 0; returns that value for subsequent frames
KEYE (KeyframeEmitterData data) Keyframe Emitter List of synchronized animation keys
KEYP (KeyframeEmitterData data) Keyframe Emitter List of percentage-tweened animation keys
MODU (IntElement a, IntElement b) Modulo Returns a % b
MULT (IntElement a, IntElement b) Multiply Returns a * b
PULS (IntElement aDuration, IntElement bDuration, IntElement a, IntElement b) Pulse Returns a for aDuration frames then b for bDuration frames, then repeats this cycle
RAND (IntElement a, IntElement b) Random Rolls a random value between a and b
SPAH (IntElement val, IntElement waitMin, IntElement waitMax) Sample And Hold Stores val for a random count of frames between waitMin and waitMax and repeats this cycle
SUB_ (IntElement a, IntElement b) Subtract Returns a - b
TSCL (RealElement dv) Time Scale Returns dv times the current frame index (rounding down to nearest integer)

Real Elements

FourCC Parameters Description Notes MP1 MP2 MP3 DKCR DKCTF
ADD_ (RealElement a, RealElement b) Add Returns a + b
CEQL (RealElement ca, RealElement cb, RealElement pass, RealElement fail) Compare Equals Returns pass if ca and cb are within 0.00001 difference, otherwise fail
CEXT (IntElement a) Unknown Involves a lookup table
CHAN (RealElement a, RealElement b, IntElement thresholdFrame) Time Chain Returns a when current frame index is less-than thresholdFrame, otherwise b
CLMP (RealElement min, RealElement max, RealElement val) Clamp Returns val clamped between min and max
CLTN (RealElement ca, RealElement cb, RealElement pass, RealElement fail) Compare Less-Than Returns pass if ca is less-than cb, otherwise fail
CNST (float value) Constant Returns value on every call
CRNG (RealElement val, RealElement min, RealElement max, RealElement inRange, RealElement outOfRange) Constant Range Returns inRange if val is between min and max, otherwise outOfRange
DOTP (VectorElement a, VectorElement b) Dot Product Returns a · b
GTCR (ColorElement color) Get Component Red Extracts red component from color
GTCG (ColorElement color) Get Component Green Extracts green component from color
GTCB (ColorElement color) Get Component Blue Extracts blue component from color
GTCA (ColorElement color) Get Component Alpha Extracts alpha component from color
IRND (RealElement a, RealElement b) Initial Random Rolls a random value between a and b on frame index 0; returns that value for subsequent frames
ISWT (RealElement a, RealElement b) Initial Switch Returns a ONLY at frame index 0, then returns b for subsequent frames
ITRL (IntElement a, RealElement b) Int Times Real Returns a * b
KEYE (KeyframeEmitterData data) Keyframe Emitter List of synchronized animation keys
KEYP (KeyframeEmitterData data) Keyframe Emitter List of percentage-tweened animation keys
LFTW (RealElement a, RealElement b) Lifetime Tween Linearly-interpolates a to b over the lifetime of the particle instance
MULT (RealElement a, RealElement b) Multiply Returns a * b
PAPn () Particle System Advance Parameter Accesses the value stored into ADV[1-8] for each system update
PRLW () Particle Rotation or Line Width Returns the rotation (in degrees) or line width for the current particle instance
PSLL () Particle Size or Line Length Returns the size or line length for the current particle instance
PULS (IntElement aDuration, IntElement bDuration, RealElement a, RealElement b) Pulse Returns a for aDuration frames then b for bDuration frames, then repeats this cycle
RAND (RealElement a, RealElement b) Random Rolls a random value between a and b
RLPT (RealElement percent) Lifetime Percent Queries the frame index at percent/100.0 into the lifetime of the particle instance
SCAL (RealElement dv) Time Scale Returns dv times the current frame index
SINE (RealElement magnitude, RealElement linearAngle, RealElement constantAngle) Sine Wave Returns sin((curFrame * linearAngle + constantAngle) * π / 180.0) * magnitude
SUB_ (RealElement a, RealElement b) Subtract Returns a - b
VMAG (VectorElement vec) Vector Magnitude Computes magnitude (length) of vec
VXTR (VectorElement vec) Vector X To Real Extracts X component of vec
VYTR (VectorElement vec) Vector Y To Real Extracts Y component of vec
VZTR (VectorElement vec) Vector Z To Real Extracts Z component of vec

Vector Elements

FourCC Parameters Description Notes MP1 MP2 MP3 DKCR DKCTF
ADD_ (VectorElement a, VectorElement b) Add Returns a + b
ANGC (RealElement angleXBias, RealElement angleYBias, RealElement angleXRange, RealElement angleYRange, RealElement magnitude) Angle Cone Generates a random vector based on (0,0,1) rotated about the X/Y axis. The angles of rotation (in degrees) are set by random ranges angleXRange and angleYRange, centered around non-random angleXBias and angleYBias. The resulting vector's length is set as magnitude.
CCLU (VectorElement circleOffset, VectorElement circleNormal, IntElement cycleFrames, RealElement randomFactor) Circle Cluster Generates a vector along an angular sweep of a unit-circle offset by circleOffset, oriented according to circleNormal. The sweep makes a full rotation within the circle over cycleFrames. The resulting vector has a randomized 3D jitter added; scaled by randomFactor times the intermediate magnitude.
CHAN (VectorElement a, VectorElement b, IntElement thresholdFrame) Time Chain Returns a when current frame index is less-than thresholdFrame, otherwise b
CIRC (VectorElement circleOffset, VectorElement circleNormal, RealElement angleConstant, RealElement angleLinear, RealElement circleRadius) Circle Generates a vector along an angular sweep of a circle of circleRadius offset by circleOffset oriented according to circleNormal. The sweep angle (in degrees) is calculated as (angleLinear * curFrame + angleConstant).
CNST (RealElement x, RealElement y, RealElement z) Constant Composes a vector from 3 float components. If all 3 components are Constant, then the internal representation is an optimized CVector3f data-structure.
CONE (VectorElement direction, RealElement baseRadius) Cone Generates a vector within a cone directed towards direction; with the cone's base limited by min(1.0, baseRadius)
CTVC (ColorElement color) Color To Vector Converts RGB components of color to a 3-component vector
KEYE (KeyframeEmitterData data) Keyframe Emitter List of synchronized animation keys
KEYP (KeyframeEmitterData data) Keyframe Emitter List of percentage-tweened animation keys
MULT (VectorElement a, VectorElement b) Multiply Returns a * b
PLCO () Previous Particle Location Accesses the location (world space) of the current particle instance on the previous frame (or current frame if at frame 0)
PLOC () Particle Location Accesses the location (world space) of the current particle instance
PSOF () Particle System Forward Accesses the local forward-pointing vector of the current particle system, oriented in world space
PSOU () Particle System Up Accesses the local up-pointing vector of the current particle system, oriented in world space
PSOR () Particle System Right Accesses the local right-pointing vector of the current particle system, oriented in world space
PSTR () Particle System Translation Accesses the translation vector (world space) of the current particle system
PULS (IntElement aDuration, IntElement bDuration, VectorElement a, VectorElement b) Pulse Returns a for aDuration frames then b for bDuration frames, then repeats this cycle
PVEL () Particle System Velocity Accesses the velocity vector (world space) of the current particle instance
RTOV (RealElement val) Real To Vector Assigns val to all 3 components of the returned vector
SUB_ (VectorElement a, VectorElement b) Subtract Returns a - b

Mod Vector Elements

FourCC Parameters Description Notes MP1 MP2 MP3 DKCR DKCTF
BNCE (VectorElement planePoint, VectorElement planeNormal, RealElement friction, RealElement restitution, bool dieOnPenetrate) Bounce Maintains the state of an unbounded plane in local space, defined by planePoint and planeNormal. If the particle's position penetrates this plane, it will either be destroyed if dieOnPenetrate is set, or a deflection will occur. This deflection accounts for friction along the plane and restitution of the objects represented by the particles.
CHAN (ModVectorElement a, ModVectorElement b, IntElement thresholdFrame) Time Chain Returns a when current frame index is less-than thresholdFrame, otherwise b
CNST (RealElement x, RealElement y, RealElement z) Constant Composes a mod vector from 3 float components. If all 3 components are Constant, then the internal representation is an optimized CVector3f data-structure. This vector overrides the particle's velocity in units/frame.
EMPL (VectorElement implodePoint, RealElement velocityScale, RealElement maxRadius, RealElement minRadius, bool enableMinRadius) Exponential Implosion Integrates a cumulative implosion force over time by influencing the velocity of particles within maxRadius of implodePoint (and outside minRadius if enableMinRadius set). The velocity of these particles is set as (particleVelocity + velocityScale * (implodePoint - particlePosition)) units/frame.
EXPL (RealElement impulseMagnitude, RealElement falloffFactor) Explode Rolls a random, normalized vector scaled by impulseMagnitude on frame 0 and sets this as the particle's velocity in units/frame. Subsequent frames multiply the velocity by falloffFactor.
GRAV (VectorElement acceleration) Gravity Integrates a simple cumulative acceleration in units/frame2
IMPL (VectorElement implodePoint, RealElement velocityScale, RealElement maxRadius, RealElement minRadius, bool enableMinRadius) Implosion Integrates a cumulative implosion force-differential over time by influencing the velocity of particles within maxRadius of implodePoint (and outside minRadius if enableMinRadius set). The velocity of these particles is set as (particleVelocity + (velocityScale / magnitude(implodePoint - particlePosition)) * (implodePoint - particlePosition)) units/frame.
LMPL (VectorElement implodePoint, RealElement velocityScale, RealElement maxRadius, RealElement minRadius, bool enableMinRadius) Linear Implosion Integrates a non-cumulative implosion force-differential over time by influencing the velocity of particles within maxRadius of implodePoint (and outside minRadius if enableMinRadius set). The velocity of these particles is set as ((velocityScale / magnitude(implodePoint - particlePosition)) * (implodePoint - particlePosition)) units/frame.
PULS (IntElement aDuration, IntElement bDuration, ModVectorElement a, ModVectorElement b) Pulse Returns a for aDuration frames then b for bDuration frames, then repeats this cycle
SPOS (VectorElement pos) Set Position Overrides the particle's position as pos
SWRL (VectorElement helixPoint, VectorElement curveBinormal, RealElement targetRadius, RealElement tangentialVelocity) SWRL Maintains a curve differential along a helix using a system derived from the Frenet–Serret formulas. The helical axis crosses through helixPoint in local space, oriented along curveBinormal. The particle's velocity is continuously updated to maintain targetRadius from the helical axis, while traveling along the curve tangent at tangentialVelocity units/frame.
WIND (VectorElement windVelocity, RealElement factor) Wind Integrates a cumulative force outside the particle's local reference; computed as ((windVelocity - particleVelocity) * factor) units/frame2

Color Elements

FourCC Parameters Description Notes MP1 MP2 MP3 DKCR DKCTF
CFDE (ColorElement a, ColorElement b, RealElement startFrame, RealElement endFrame) Fade End Returns a before startFrame and b after endFrame, otherwise a linear-interpolation from a to b in-between.
CHAN (ColorElement a, ColorElement b, IntElement thresholdFrame) Time Chain Returns a when current frame index is less-than thresholdFrame, otherwise b
CNST (RealElement r, RealElement g, RealElement b, RealElement a) Constant Composes a color from 4 float components. If all 4 components are Constant, then the internal representation is an optimized CColor data-structure.
FADE (ColorElement a, ColorElement b, RealElement endFrame) Fade Returns b after endFrame, otherwise a linear-interpolation from a to b between frame 0 and endFrame.
KEYE (KeyframeEmitterData data) Keyframe Emitter List of synchronized animation keys
KEYP (KeyframeEmitterData data) Keyframe Emitter List of percentage-tweened animation keys
PCOL () Particle Color Accesses the color of the current particle instance
PULS (IntElement aDuration, IntElement bDuration, ColorElement a, ColorElement b) Pulse Returns a for aDuration frames then b for bDuration frames, then repeats this cycle

UV Elements

ATEX example.png ATEX example crunchy.gif

Example of an ATEX map used in the closing cinematic (spoilers)
FourCC Parameters Description Notes MP1 MP2 MP3 DKCR DKCTF
CNST (TXTR tex) Constant References tex for sampling using constant UV rectangle points (0,0) (1,1)
ATEX (TXTR tex, IntElement tileW, IntElement tileH, IntElement strideW, IntElement strideH, IntElement cycleFrames, bool loop) Animated Texture References tex for sampling using UV tiles scanned left-to-right, top-to-bottom as individual frames of animation. The UV coordinates are scaled and offset using the tile and stride parameters in texels. All tiles of the image are played over the course of cycleFrames. If loop is set, the tiles repeat, otherwise lingers on the final tile.

Emitter Elements

FourCC Parameters Description Notes MP1 MP2 MP3 DKCR DKCTF
SETR/SEMR (VectorElement position, VectorElement velocity) Simple Emitter Directly initializes new particle instances with position and velocity arguments. The only difference with SETR is the position argument is tagged with ILOC and velocity is tagged with IVEC, theoretically making the parameters optional or re-orderable.
SPHE (VectorElement sphereOrigin, RealElement sphereRadius, RealElement velocity) Sphere Randomly initializes new particle positions along the surface of a sphere defined by sphereOrigin and sphereRadius. The resulting velocity vector is computed from the sphereOrigin to this random point, with the magnitude set as velocity.
ASPH (VectorElement sphereOrigin, RealElement sphereRadius, RealElement velocity, RealElement angleXBias, RealElement angleYBias, RealElement angleXRange, RealElement angleYRange) Angle Sphere Randomly initializes new particle positions along the surface of an angular sphere-section defined by sphereOrigin and sphereRadius. The angular section is based on position (0,0,1) rotated about the X/Y axis, randomized within angleXRange and angleYRange centered around angleXBias and angleYBias. The resulting velocity vector is computed from the sphereOrigin to this random point, with the magnitude set as velocity.

Keyframe Emitter Template

KEYE and KEYP elements statically encode a list of key values for all element types (except Mod Vector, UV and Emitter elements). T represents the type being encoded.

Data Type Description Notes
u32 Percentage-Tweening Flag If non-zero, this is a KEYP and there are exactly 101 keys in the list; all of these keys are linearly-interpolated over the lifetime of the particle instance (however long that may be)
u32 Unknown Not used by GetValue
u8 Loop Flag If non-zero, the key values are looped between loopStart and loopEnd indices (does not apply to KEYP)
u8 Unknown Not used by GetValue
u32 Loop End Final key index in the loop
u32 Loop Start First key index in the loop
u32 Key Count Count of keys encoded in the list
T[keyCount] Keys The actual key values themselves