PART (File Format)

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

The PART particle script format is used to configure particle effects.

Particles are the most widely-used effect in Metroid Prime, with approximately 3,500 unique scripts across the PAK archives. Each script configures a complete particle system that may draw into the scene.

The particle system is configurable to generate many visual effects:

  • Flames and smoke
  • Floating embers
  • Water splashes/drips
  • Dust and dirt in windy conditions
  • Volumetric light "shimmers"
  • Energy/plasma discharges
  • Many others

The concept behind the particle system is quite simple: lots of view-aligned (camera-facing) quads with a texture-image are emitted, positioned, rotated, sized, colored, etc... according to the parameters in the particle script.

Particle System

The particle system ties together all procedures necessary to host an emitter and specifies the rate at which new particles should be created. New particles have a predetermined lifetime (in frames) set by the system, and the emitter initializes the position and velocity of these particles. The system continuously updates all currently-living particles that it's created. This includes updating properties like position, velocity, color, size and view-rotation.

Child Systems

Particle systems may also host child systems which are timed and positioned within the parent's reference. Not only does this include other PART systems, but SWHC and ELSC systems may be parented as well.

A good example of this is the flamethrower's system, which composes flame particles with a trailing SWHC and small cinders from a separate PART.

Line Mode

When the LINE property is activated, particles are rendered as lines rather than quads.

The usual 3D particle position is used as the trailing-point of the line, with the leading-point computed via positional-differential, scaled by other parameters. Lines sample textures diagonally as a single-texel strip, allowing for gradients to be applied via spherical or diagonal ramp-textures.

Model Mode

When the PMDL property is provided with a CMDL, particles are rendered using that model, in addition to the quad. Alternatively, PMUS generates a quad transformed as if it were a model (non view aligned).

Model-based particles have a whole separate suite of properties for controlling local-transformation and color. Most of the properties involving positioning and transforms from the client systems are shared from the normal quad-mode.

Many weapon effects, notably the "sphere" of the charge-beam, are accomplished using particle models.

Particle Instance

For each frame, each particle does the following primary tasks:

  • Determines if particle's lifetime has finished, removing it from the scene and releasing its resources for newly created particles to use
  • Invokes all velocity/position sources; advancing position 1/60th of a second
  • Evaluates local transforms
    • Size
    • View-aligned rotation
    • View-aligned offset
  • Evaluates particle color (shader-multiplied with texture-image)

Emitter

Main article: Emitter Elements

Each particle-system employs a single emitter context. The system generates a specified number of particles each frame; the emitter initializing the position and velocity-vector for each.

Properties

Particle generator properties are assembled into a particle script file tagged with GPSM. Any of the following properties are loaded into a description class for constructing an arbitrary number of particle generators.

FourCC Type Description Scope Notes MP1 MP2 MP3 DKCR DKCTF
PSIV VectorElement System Initial Velocity System Init Defines the initial velocity vector which moves the entire system in local orientation (may be overridden by PSVM) Demo
PSVM ModVectorElement System Velocity Mod Post Particles Update Mod Vector which influences the position and velocity of the entire system in local space Demo
PSOV VectorElement System Orientation Velocity Post Particles Update Angular velocity (in degrees/frame) of the system's orientation Demo
PSLT IntElement System Lifetime System Init Count of frames that the system generates new particles
PSWT IntElement System Warmup Time Warmup-Phase Update Count of frames that the particle system virtually updates itself within one initial frame; exiting the warmup phase afterwards
PSTS RealElement System Time Scale Pre Particles Update Factor that redefines the second for the system, including the rate at which the system's frame count is incremented. 1.0 is native 60-fps. 0.5 causes every other frame to skip updates, slowing down and making the motion "choppy". 2.0 causes 2 updates every frame, speeding up.
POFS VectorElement Particle Offset System Init, Post Particles Update Vector that offsets all particles in world space
SEED IntElement Random Seed System Init Value used to initialize the LCG seed state used within the system's update and render cycles (default 99)
LENG RealElement Line Length Line Particle Creation, Line Particle Update Length of LINE particles, scaled according to FXLL
WIDT RealElement Line Width Line Particle Render Width of LINE particles in viewport pixels
MAXP IntElement Max Particles System Init, Pre Particles Update Max count of particles allowed to live at once. No new particles created if there are already this many active particles.
GRTE RealElement Generation Rate Pre Particles Update Count of particles to create each frame. Remainder value is accumulated for the next update cycle.
COLR ColorElement Color Particle Creation, Particle Update Color to multiply with particle's texture
LTME IntElement Lifetime Particle Creation Count of frames the about-to-be-created particle lives
ILOC VectorElement Particle Emit Location Particle Creation Position to initialize particle in local space (replaced by EMTR) Demo
IVEC VectorElement Particle Emit Velocity Particle Creation Velocity to initialize particle in local space (replaced by EMTR) Demo
EMTR EmitterElement Emitter Particle Creation Modular data source for initializing position and velocity of new particles
LINE bool Line Mode System Init Render particles as lines instead of quads
FXLL bool Line Mode System Init Scale leading point of line as the exact value of LENG, rather than multiplying LENG with the position-differential
AAPH bool Additive Alpha System Init Set up blending of quads and lines with source factor of GX_BL_SRCALPHA and destination factor of GX_BL_ONE as opposed to GX_BL_SRCALPHA and GX_BL_INVSRCALPHA
ZBUF bool Z-buffer Write System Init Perform rendering while writing into the z-buffer to ensure later-drawn objects don't occlude particles if positioned behind them
SORT bool View-space Sort System Init Sort particles by their z-coordinate in view-space before drawing, which is essential for proper alpha blending (although mathematically unnecessary when AAPH is active)
LIT_ bool Unknown System Init Unused in demo
ORNT bool Orient To Origin System Init New in retail - Simultaneously orients particle instances toward the local origin and view-point via cross-product. ROTA is used to control the width of quads in this mode, while SIZE controls the length.
RSOP bool Right Vector Scaled on Particle System Init New in retail - The right vector (particle width) is proportionally scaled with length
MBLR bool Motion Blur System Init Enables sub-positional overdraw of each particle instance between its previous position and new position each frame; draw count controlled by MBSP
PMAB bool Model Additive Alpha System Init Equivalent of AAPH for models and PMUS quads
PMUS bool Model Unoriented Square System Init Draws a 1x1 quad in the XZ-plane in place of a PMDL model
PMOO bool Model Object Orientation System Init Includes client-supplied orientation in model's transform chain (after PMRT). Unlike other bool properties, this property is enabled by default
VMDn bool Local Vector Mod [1-4] System Init Applies mod vectors VELn in system local-space rather than world-space
CIND bool Colored Indirect Texture System Init When TIND is active, texels copied from the underlying framebuffer are multiplied with the texels in TEXR (rather than added). The alpha component is always multiplied.
OPTS bool Optional System System Init When a client system constructs a generator instance, it has the option to filter out child systems at any level that aren't essential to the effect. The exclusion is a mutual decision between the client and the particle description via this property.
MBSP IntElement Motion Blur Samples Pre Particles Update When MBLR is active, this is the number of times the position differential of each particle instance is subdivided for overdraw
SIZE RealElement Particle Size Particle Creation, Particle Update Proportional scale (length and width) of particle quads
ROTA RealElement Particle View-Rotation Particle Creation, Particle Update View-aligned counterclockwise-rotation of particle instances
TEXR UVElement Particle Texture Particle Creation, Particle Update Particle texture map and UV coordinate source
TIND UVElement Indirect Particle Texture Particle Creation, Particle Update Indirect texture map and UV coordinate source. Setting this property enables framebuffer->texture copies of the rectangular region behind particle instances. These texels are warped using coordinates defined in the texels of the IA texture in this property.
PMDL CMDL Particle Model System Init Render particle instances using this model, in addition to quads
PMOP VectorElement Particle Model Pre-Offset Particle Model Render Translate models using this vector before transforming normally
PMRT VectorElement Particle Model Rotate Particle Model Render Rotate models using these euler angles (in degrees, ZYX order)
PMSC VectorElement Particle Model Scale Particle Model Render Scale models using this (potentially non-proportional) vector
PMCL ColorElement Particle Model Color Particle Model Render Multiply textured model color with this color
VELn ModVectorElement Particle Mod Vectors [1-4] Particle Update Up to 4 mod vectors invoked (in order) on each particle instance for each frame; influencing position and velocity
ICTS PART Counted Child System System Init Child particle system to spawn multiple instances of
NCSY IntElement Counted Child System Count System Init Count of ICTS systems to spawn (default 1)
CSSD IntElement Counted Child System Frame System Init Frame index to spawn ICTS instances
IDTS PART Done Child System System Init Child particle system to spawn multiple instances of when parent system's lifetime finishes
NDSY IntElement Done Child System Count System Init Count of IDTS systems to spawn (default 1)
IITS PART Interval Child System System Init Child particle system to spawn at regular intervals
PISY IntElement Interval Child System Frame Interval System Init Frame interval to emit IITS instances
SISY IntElement Interval Child System Start Frame System Init Frame index to start emitting IITS instances
KSSM SpawnSystemKeyframeData Timed-Spawn Particle Systems System Init List of start-frame events and corresponding child systems to spawn
SSWH SWHC Child Swoosh System System Init Child swoosh system parented to this system
SSSD IntElement Child Swoosh System Start Frame System Init Frame index to start emitting SSWH
SSPO VectorElement Child Swoosh System Offset System Init Offset supplied as swoosh system's translation
SELC ELSC Child Electric System System Init Child electric system parented to this system
SESD IntElement Child Electric System Start Frame System Init Frame index to start emitting SELC
SEPO VectorElement Child Electric System Offset System Init Offset supplied as electric system's translation
LTYP IntElement System Light Type System Init Type of GX light to parent to system
  1. None (no light)
  2. Custom (point)
  3. Directional
  4. Spot
LCLR ColorElement System Light Color Post Particles Update Diffuse color of GX light
LINT RealElement System Light Intensity Post Particles Update Light intensity factor used for calculating falloff
LOFF VectorElement System Light Offset Post Particles Update Light offset (not applicable to directional lights)
LDIR VectorElement System Light Direction Post Particles Update Light direction (not applicable to custom lights)
LFOT IntElement System Light Falloff Type System Init Type of linear-attenuation equation to use for light
  1. Constant
  2. Linear
  3. Quadratic
LFOR RealElement System Light Falloff Radius Post Particles Update Falloff radius for linear-attenuation (not applicable to constant)
LSLA RealElement System Light Cutoff Angle Post Particles Update Cutoff angle for angular-attenuation (only applicable to spot)
ADVn RealElement Advance Parameters [1-8] Pre Particles Update Parameters to compute per system update, values shared across all particle instances via PAPn real elements

SpawnSystemKeyframeData

Data Type Description Notes
u32 Unknown
u32 Unknown
u32 End Frame Final frame index where a system is spawned
u32 Unknown
u32 List Count
{u32 frame, u32 infoCount, SpawnSystemKeyframeInfo[infoCount]}[listCount] Lists Pairs of frame index and sequence of SpawnSystemKeyframeInfo for grouping systems that start on the same frame

SpawnSystemKeyframeInfo

Data Type Description Notes
PART Child System ID
u32 Unknown
u32 Unknown
u32 Unknown