# Particle Script .PRT

by Christoph Kubisch

## Content

- Definition
- Example
- Renderflag
- Emitter
- Particle
- Color
- Texture
- Forces
- Subsystems
- History

## Definition

A particlesystem script allows easier setup of particles and defines how they behave. Particles are always drawn last within a scene.

When a script is used, the emitter, or source partile for trails, will hand over following fixed attributes:

- position
- direction

Depending on this information the values defined in a script are relative to.

Emitter & Particle must be defined in a script, the rest is optional

Variances are computed as followed:
out = random between [in-variance,in+variance]
Agefx are uint 0-99 = 0%-99% of lifetime
Agetextures are not loaded into resource textures, but only for initialization. If you want to change the values afterwards, use api calls on the particlesystem

### Branching

You can do branching with following commands. Enclose the branches in curly brackets { }

- IF:<condition string>
- ELSEIF:<condition string>
- ELSE

The condition string can be set from luxinia API with resource.condition.
You can also negate a statement with !<condition string>.
Be aware that the parser is not fully rock solid, so at best use COMMAND{<newline> <what><newline> }<newline> , when problems occur.

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## Example

luxinia_ParticleSys_v110 RenderFlag{ # this is a comment blah blendmode VID_ADD; sort; } Emitter{ type VID_POINT; size 10; spread (0,45); rate 170; velocity 30; count 100; maxoffsetdist 200; } Particle{ type GL_POINTS; size 1; life 5000; } Texture{ numtex 2; TEX 0 "test0.jpg"; TEX 50 "test1.jpg"; } Color{ numcolor 1; RGBA 100 (1.0,0.3,0.3,0.5); } Forces{ gravity 1000 (0.0,-10.0,0.0) 5; } SubSystem{ trail "blubb.prt" 500 VID_DIR 40 100; }

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## RenderFlag

they are applied to all particles and are optional.

- nodraw;
  this system wont be drawn but subsystems would useful if you want to hide the source system for trailsubsystems
- lit;
  particles are lit (default off)
- depthmask;
  will write into depthmask (ie. depth information stored, default off)
- nodepthtest;
  will do no depth testing (ie. always on top when drawn)
- alphamask;
  quick for: alphafunc GL_GREATER (0.0)
- sort;
  will sort the particles by z-value
  if blendfunc is defined then back to front
  if alphafunc is set then front to back
  if both are set front to back is taken
- novistest;
  if set we will do no visibility testing but always update the emitters
- alphafunc <enum func> (<float ref>);
  to cap transparency of an object, same as in ShaderScript
- blendmode <enum blendmode>;
  to make soft blends
  - blendmode
    VID_MODULATE out = self * in
    VID_ADD out = self + in
    VID_AMODADD out = self * self.alpha + in
    VID_DECAL out = self * self.alpha + in * (1-self.alpha)
- nocull;
  disables culling

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## Emitter

How the particles are emitted is defined in here. What you define is just the default emitter. During runtime when you create new emitters you can change their type and properties individually.

### Mandatory:

- type <type enum>;
  what the source of particles is
  - VID_POINT
    just a simple point
    startvelocity = emitterdirection * velocity
  - VID_CIRCLE
    a flat circle area with its normal in emitterdirection
    the size must be specified, particle will spawn somewhere within the circle
    startvelocity = emitterdirection * velocity
  - VID_SPHERE
    along the sphere surface, radius must be specified
    startvelocity = sphere's normal * velocity
  - VID_RECTANGLE
    along the axis aligned rectangle surface. Uses world axis for the plane. needs axis, width and height set
    startvelocity = emitterdirection * velocity
  - VID_RECTANGLELOCAL
    along the local aligned rectangle surface. Uses local X- and Z- axis of emitter for the rectangle plane. needs width and height set
    startvelocity = emitterdirection * velocity
  - VID_MODEL
    spawns on a random vertex of given model
    startvelocity = vertex normal * velocity
- count <num uint>;
  total particles that can be displayed, you should somewhat find a good optimum how many you really need. Maximum is 8192
- size <radius float>;
  sphere or circle radius
- width <radius float>;
  width of VID_RECTANGLE
- height <radius float>;
  height of VID_RECTANGLE
- axis <int 0-2>;
  axis of the plane's normal for VID_RECTANGLE, 0 = X, 1 = Y, 2 = Z
- model "<modelfile string>";
  modelfile of VID_MODEL
- rate <rate uint>;
  how many particles per second one emitter spawns

### Optional

- velocity <vel float>;
  the starting velocity, units per second
- endtime <time uint>;
  time in ms after creation it will stop emission, if 0 then constantly spawned, or user controlled
- maxoffsetdist <dist float>;
  random offset from original spawnposition in velocity direction
- velocityvar <var float>;
  variance to velocity
- flipdirection <percent float>;
  percent of how many particles will use opposite direction
- spread (<inner degrees uint>,<outer degrees uint>);
  variance added to emitterdirection, maximum angle a random direction can have from original direction, particle direction will be between inner and outer angle.
- restarttime <time uint>;
  time in ms after endtime when particles are spawned again
- restarts <num uint>;
  how often restarts will happen 1-254, 255 = infinite

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## Particle

This defines the appearance of the particle and certain variances to it.

### Mandatory

- type <geo enum>;
  this defines the particle appearance
  - VID_POINT
    a simple point, implementation may vary on gl_driver. When gl_driver allows point sprites a single texture can be used. Particlesize will be in pixels on screen at 640x480. Particles cannot have individual sizes.
  - VID_QUAD
    a flat quad facing towards camera, e.g part | > eye. origin at center
  - VID_TRIANGLE
    a flat triangle facing towards camera
  - VID_HSPHERE
    a 5-sided hemisphere facing towards camera, e.g part ) > eye
  - VID_SPHERE
    a sphere (non textureable)
  - VID_MODEL
    a model, must be specified, particles will randomly pick a mesh inside the model and use its material, very expensive
- model "<modelfile string>";
  if VID_MODEL was picked as particle type, tell which model to use
- life <time uint>;
  time in ms until particle death
- size <size float>;
  size of particle (pixel,radius,width, model scale)

### Optional

- instancemesh "<string meshname>";
  if VID_MODEL is used, you can create instancing effects using a single mesh from the model.
  Only small meshes (quads/triangles,max 32 vertices and 96 indices) can be instanced. If successful,
  all particles will use the same mesh.
  The purpose of using a single instancemesh is speeding up rendering of lightweight meshes.
- originoffset (<x float>,<y float>,<z float>);
  if VID_QUAD,TRIANGLE,INSTANCEMESH,HSPHERE are used you can offset the drawing center by this vector
- sizevar <percent float>;
  size variance, minimum size is 1/10 of original
- lifevar <percent float>;
  variance in the lifetime
- rotate <degrees uint> <dir enum>;
  rotates particle around center.
  - degrees
    degrees per second
  - direction
    VID_POS, VID_NEG, VID_RAND
- rotatevar <percent float>;
  variance to rotation degree
- rotateoffset <degrees uint>;
  angle on start is random(0 - degrees)
- rotatevelocity;
  if this flag is set rotation is linked to particle velocity
- dieonfrontplane;
  if flag is set particle will die when behind camera
- camrotfix;
  if set we will rotate particles based in which direction the camera looks. Useful for getting rid of billboard alignment in top down situation.
  overriden by rotatevelocity. Another solution is using Luxinia Api and make the particles globally aligned.
- noagedeath;
  if flag is set particle will not die if too old, but get age of 0 again
- pointsmooth;
  if flag is set particles will be rendered as antialiased round dots
- pointparams (<float minsize>,<float maxsize>)(<float alphathresh>)(<float const>,<float lin>,<float square>);
  for points special parameters can be set to control size by distance attenuation.
  outsize = size * 1/(const + lin*distance + square*distance*distance)
  - minsize,maxsize
    outsize will be capped by these values
  - alphathresh enables a fading out of color.alpha when size gets below thresh
  - cons,lin,square
    distance attenuation parameters

Age-Based Effects

- sizeage3 <age1 uint> (<size1 float>) <age2 uint> (<size2 float>) <age3 uint> (<size3 float>);
  can control the size changing over time, size will grow/shrink depending on the values
  there is 3 size groups, each size group contains
  - age
    time in percent of totallife
  - size
    size multiplier of the particle
- speedage3 <age1 uint> (<velm1 float>) <age2 uint> (<velm2 float>) <age3 uint> (<velm3 float>);
  scale velocity based on age
- rotateage3 <age1 uint> (<rotm1 float>) <age2 uint> (<rotm2 float>) <age3 uint> (<rotm3 float>);
  can control the rotation changing over time. It works as multiplier of original rotation.
- sizeagetex "<texturefile string>" <row uint> (<scale float>) <subtract float>;
  can control the size changing over time, size will grow/shrink depending on the values, pixel 0 = start, 127 = end.
  - texturefile
    The texture must be 128 pixels wide, and ideally be a .tga file or other losless format.
  - row
    the row within the texture to use (you can combine multiple effects in one texture)
  - scale
    each value in the texture represents 0.0 - 1.0 (we take the R value in RGB/RGBA). you can scale this
    value with the given parameter. e.g. scale = 2 you will get 0.0 - 2.0.
  - subtract
    this optional value will be subtracted from texture*scale, that way you can create sign changes if needed;
- rotateagetex "<texturefile string>" <row uint> (<scale float>) <subtract float>;
  can control the rotation changing over time. It works as multiplier of original rotation.
- speedagetex "<texturefile string>" <row uint> (<scale float>) <subtract float>;
  scale velocity based on age

Content

## Color

In here the color of the particles are set. If no color is set default will be white.

### Mandatory

- numcolor <number uint>;
  the number of colors a particle can have, must be specified first, minimum is 1
- RGBA <age uint> (<R cfloat>,<G cfloat>,<B cfloat>,<A cfloat>);
  **age
  in percent of totallife, if just one color is given this is ignored **R G B A
  is color/alpha value
- RGBAagetex? "<texturefilename string>" <uint row>;
  instead of numcolor & RGBA this single command can be used. The 128 pixel wide texture contains all color values, 0 = start, 127 = end.
  - row
    the pixelrow to use within the texture;

### Optional

- noage;
  if flag is set colors will be picked randomly for a new particle
- interpolate;
  if flag is set then colors will be interpolated between ages
- RGBAvar (<percentR float>,<percentG float>,<percentB float>,<percentA float>);
  to add random variance to each color value, +/- SRC * var + SRC

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## Texture

Same as color, if non is set we assume no texture given textures cannot have texshaders applied, and must all be same size,same format. Mind that depending on graphics card errors can come up with too many squence images.

### Mandatory:

- numtex <number uint>;
  the number of textures, must be specified first
- MATERIAL/TEX/TEXALPHA <age uint> "<texname string>";
  - age
    in percent of totallife, if just one texture is given this is ignored
  - texname
    is the filename in a relative path
  - TEX RGB/RGBA
  - TEXCOMBINE1D/2D_16/2D_32 RGB/RGBA
    we assume always the first specified texture is used, and has already horizontally(1d) or square(2d) combined textures in it.
  - TEXALPHA ALPHA
  - MATERIAL
    a single material is used for all textures, the textures used in the material are combined images by the user and must contain power of 2 subimages. using combine draw with materials is not allowed. All should be of same type (the last will be used for all)

### Optional

- eventimed;
  if flag was set before you start with the textures, they will all get same difference in time.
  when you use TEXCOMBINEx or MATERIAL you wont have to specify the other textures, ie a single entry will be enough
- noage;
  if flag is set random texture is picked for new particle
- sequence;
  if flag is set the defined textures are taken as a loopable sequence time delay of first is added to last
  e.g: 10 "a" 20 "b" 30 "c" → 10 "a" 20 "b" 30 "c" 40 "a" 50 "b" 60 "c" ... until 100
- agetex "<texturefile string>" <row uint>;
  which texture is used at what timestep is encoded in the texture, we use the pixel values and modulo them with numtex.
  - row

the pixelrow within the texture, in (RGB/RGBA textures R is used)

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## Forces

Forces influence the particle motion, maximum is 32 forces per system.

There are more force types creatable by Luxinia Api such as

- magnet
  range based attraction/repulsion of particles. Uses quadratic distance falloff to target for effect strength.
- target
  similar to magnet, but without range falloff.

Standard forces:

- gravity (<x float>,<y float>,<z float>) <turbulence float> [<uint starttime>] [<uint endtime>] ["<string name>"];
  contains information of gravity, gravity is constant acceleration
  - (x,y,z)
    define direction and strength in world coordinates
  - turbulence
    is a wavey translation
- wind (<x float>,<y float>,<z float>) <turbulence float> <airres float> [<uint starttime>] [<uint endtime>] ["<string name>"];
  - (x,y,z)
    define direction and strength in world coords, x,y ground plane
  - turbulence
    is a wavey translation
  - airres
    air resistance a particle wind is either accelerating or slowing down depending on particle velocity same as above

### Optional

  - starttime
    the minimum age a particle must have to be affected
  - endtime
    the maximum age to be affected by force
  - name
    the name handle (less than 16 characters). Useful if you want to access the force from Luxinia api.

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## SubSystem

With this other particle systems can be generated, maximum 4. The subsystems are drawn as listed after the original system, however if combinedraw flag is set they will get drawn with a single call.

- combinedraw;
  a special flag that will put all particles into a single draw call. however all textures must be same type (RGB/RGBA) and only the renderflag of the original system is used
  Also it will use particletype of root system, if subsystems have subsystems themselves combinedraw will be ignored for all.

- trail "<psysname string>" <delay uint> <dir enum> <minage uint> <nth uint>;
  particle will leave a trail of of the specified particles from the particles of us
  - psysname
    filename of subsystem
  - delay
    time in ms until subsys is launched
  - dir
    VID_DIR particle's direction
    VID_ODIR opposite of direction
  - minage
    minage of particle to leave a trail
  - nth
    every nth particle will create a trail

- normal "<psysname string>" <delay uint>;
  psys will be generated after a time given, direction & position is same as original
  - psysname
    filename of subsystem
  - delay
    time in ms until subsys is launched

- translated "psys.prt" <delay uint> (<px float>,<py float>,<pz float>) (<dx float>,<dy float>,<dz float>);
  similar to normal system but with specific position and direction, position is relative to original position
  - delay
    time in ms until subsys is launched
  - (px,py,pz)
    position vector
  - (dx,dy,dz)
    direction vector is multiplied with original direction, eg. if you want the same direction then (1,1,1) would be used, if opposite (-1,-1,-1)

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## History

1st Draft 20.6.2004
This is just a basic idea about functionality. Depending on how hard it will be to do all, and how fast things can be done, the actual system may change. Also its not sure how the Trail system is done, it may done completely different, ie code uses point emitters from a different particle system.

2nd Draft 21.6.2004
Some more changes, mostly moving variables from code into the script to make them fixed. Also throwing the old trail out and instead added a subsystem of particles that will be loaded and controlled by this system.

3rd Draft 8.6.2004
Minor fiddling with the subsystems, mostly just changing minor stuff. It is yet unsure how force turbulences will look like. The other uncertainty is particles' directions

4th Draft 20.9.2004
subsystems can now be thrown into the same sorted drawlist using "combinedraw" flag

5th Draft 22.9.2004
added particle rotation

6th Draft 27.9.2004
added texture sequence

7th Draft 22.12.2004
vectors are packed in () and separated by ,

8th Draft 13.1.2005
added rotation age effect

9th Draft 28.1.2005
use of VID blendmodes

10th Draft 04.4.2005
added flipdirection percentage

11th Draft 11.6.2005
die on backplane

12th Draft 14.6.2005
added start offset, point sprites, point smoothing and pointparams

14th Draft 10.8.2005
added MATERIAL as texture type

15th Draft 6.9.2005
trails allow any emitter type now

16th Draft 12.11.2005
removed delay in forces, for simplicity / better parallelism

17th Draft 10.3.2006
removed magnets, those are handled by lua

18th Draft 13.3.2006
changed the way forces are dealt with, timed forces are back

19th Draft 4.6.2006
agebased effects can now be read from the texture

20th Draft 14.6.2006
added originoffset vector for billboards

21st Draft 20.6.2006
particle mesh instancing added

22nd Draft 10.8.2006:
added "preprocessor" branching

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