User:Jackoalan/PART (File Format)

This file format is almost completely documented Key descriptions are subject to corrections

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.

PART 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	Unknown	System Init	New in retail - Needs to be discovered	✔	✔	✔	✔	✔
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.	✔	✔	✔	✔	✔
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.	✔	✔	✔	✔	✔