llParticleSystem
Revision as of 15:00, 22 January 2010 by Talarus Luan (talk | contribs) (Fixed incorrect PSYS_PART_FOLLOW_VELOCITY_MASK description.)
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Summary
Function: llParticleSystem( list rules );| 0.0 | Forced Delay |
| 10.0 | Energy |
Defines a particle system for the containing prim based on a list of rules.
| • list | rules | – | Particle system rules list in the format [ rule1, data1, rule2, data2 . . . rulen, datan ] |
Specification
Defines a particle system that sets the state of the particle emitter within the prim which the script is contained. Any other scripts in the same prim which call this function will modify the state of the same particle emitter. As such, the particle system defined by this function is a prim property, just like its size, shape, color, et cetera. Each prim has only one (1) particle emitter, located at its geometric center, and aligned along the prim's local Z-axis, pointing in the positive Z direction.
This is the only function which alters the state of the prim's particle emitter; thus, if you wish to change the emitter to a different state (i.e., emitting a different particle system entirely, or shut off the emitter completely), just call this same function with the parameters of the new particle system you wish to render instead. Specifying an empty list (i.e., llParticleSystem([]); ) turns the emitter off.
Particles are essentially 2D "sprites" and are always rendered facing the viewer's camera.
The rule / data values are defined below.
| Rule / Value Constant | Type | Description | Value | |
| System Behavior | ||||
| PSYS_PART_FLAGS | integer | Various flags controlling the behavior of the particle system. The value may be specified as an integer in decimal or hex format, or by ORing together (using the | operator) one or more of the following flag constants: | 0 | |
| V a l u e s |
PSYS_PART_BOUNCE_MASK | When set, specifies particles will bounce off a plane at the region Z height of the emitter. On "bounce", each particle reverses velocity and angle. This only works for particles above the plane falling down on it. | 0x004 | |
| PSYS_PART_EMISSIVE_MASK | When set, particles are full-bright and are unaffected by global lighting (sunlight). Otherwise, particles will be lit depending on the current global lighting conditions. Note that point lights do illuminate non-emissive particles. | 0x100 | ||
| PSYS_PART_FOLLOW_SRC_MASK | When set, particles move relative to the position of the emitter. Otherwise, particle position and movement are unaffected by the position/movement of the emitter. This flag disables the PSYS_SRC_BURST_RADIUS rule. | 0x010 | ||
| PSYS_PART_FOLLOW_VELOCITY_MASK | When set, particles rotate to orient their "top" towards the direction of movement or emission. Otherwise, particles are oriented vertically as their textures would appear (top of texture at top, left at left). | 0x020 | ||
| PSYS_PART_INTERP_COLOR_MASK | When set, particle color and alpha transition from their START settings to their END settings during the particle's lifetime. The transition is a smooth interpolation. | 0x001 | ||
| PSYS_PART_INTERP_SCALE_MASK | When set, particle size/scale transitions from its START setting to its END setting during the particle's lifetime. | 0x002 | ||
| PSYS_PART_TARGET_LINEAR_MASK | When set, emitted particles move in a straight line towards the target specified by the PSYS_SRC_TARGET_KEY rule. In this mode, PSYS_SRC_ACCEL, PSYS_SRC_BURST_RADIUS, and possibly other rules are ignored. | 0x080 | ||
| PSYS_PART_TARGET_POS_MASK | When set, emitted particles change course during their lifetime, attempting to move towards the target specified by the PSYS_SRC_TARGET_KEY rule by the time they expire. Note that if no target is specified, the target moves out of range, or an invalid target is specified, the particles target the prim itself. | 0x040 | ||
| PSYS_PART_WIND_MASK | When set, particle movement is affected by the wind. It is applied as a secondary force on the particles. | 0x008 | ||
| (unimplemented) mask but in the enum | 0x200 | |||
| Used by the viewer to keep HUD and World particle sources separate. | 0x40000000 | |||
| Removes particles, not compatible with any other PSYS_PART_*_MASK | 0x80000000 | |||
| (unimplemented & commented out) Presumed to be used to apply random acceleration to the particles. | - | |||
| (unimplemented & commented out) Presumed to be used to specify random velocity for the particles upon emission. | - | |||
| (unimplemented & commented out) Presumed to be used for implementing "trails" via emitting more particles at shorter bursts. | - | |||
| System Presentation | ||||
| PSYS_SRC_PATTERN | integer | Specifies the general emission pattern. | 9 | |
| V a l u e s |
PSYS_SRC_PATTERN_ANGLE | Present particles in a 2-dimensional circular section as defined by PSYS_SRC_ANGLE_BEGIN and PSYS_SRC_ANGLE_END. The orientation of the particle plane is at X=0 relative to the emitter's region rotation. | 0x04 | |
| PSYS_SRC_PATTERN_ANGLE_CONE | Present particles in a 3-dimensional spherical section, as defined by PSYS_SRC_ANGLE_BEGIN and PSYS_SRC_ANGLE_END. | 0x08 | ||
| PSYS_SRC_PATTERN_ANGLE_CONE_EMPTY | (unimplemented) Present particles in a 3-dimensional spherical section, as defined by PSYS_SRC_ANGLE_BEGIN and PSYS_SRC_ANGLE_END, but inversely compared to the ANGLE_CONE pattern (i.e., where there were voids in ANGLE_CONE, there are particles in ANGLE_CONE_EMPTY, and vice-versa. | 0x10 | ||
| PSYS_SRC_PATTERN_DROP | Present particles by dropping them at the emitter position with no force. Ignores the PSYS_SRC_BURST_RADIUS, PSYS_SRC_BURST_SPEED_MIN, and PSYS_SRC_BURST_SPEED_MAX rules. | 0x01 | ||
| PSYS_SRC_PATTERN_EXPLODE | Present particles by shooting them out in all directions according to the burst motion rules. | 0x02 | ||
| PSYS_SRC_BURST_RADIUS | float | Specifies the distance from the emitter where particles will be created. This rule is ignored when the PSYS_PART_FOLLOW_SRC_MASK flag is set. A test in http://forums.secondlife.com/showthread.php?t=226722 indicates that the maximum value is 50.00 | 16 | |
| PSYS_SRC_ANGLE_BEGIN | float | Specifies a half angle, in radians, of a circular or spherical "dimple" or conic section (starting from the emitter facing) within which particles will NOT be emitted. Valid values are the same as for PSYS_SRC_ANGLE_END, though the effects are reversed accordingly. If the pattern is PSYS_SRC_PATTERN_ANGLE, the presentation is a 2D flat circular section. If PSYS_SRC_PATTERN_ANGLE_CONE or PSYS_SRC_PATTERN_ANGLE_CONE_EMPTY is used, the presentation is a 3D spherical section. Note that the value of this parameter and PSYS_SRC_ANGLE_END are internally re-ordered such that this parameter gets the smaller of the two values. | 22 | |
| PSYS_SRC_ANGLE_END | float | Specifies a half angle, in radians, of a circular or spherical "dimple" or conic section (starting from the emitter facing) within which particles will NOT be emitted. Valid values are 0.0, which will result in particles being emitted in a straight line in the direction of the emitter facing, to PI, which will result in particles being emitted in a full circular or spherical arc around the emitter, not including the "dimple" or conic section defined by PSYS_SRC_ANGLE_BEGIN. If the pattern is PSYS_SRC_PATTERN_ANGLE, the presentation is a 2D flat circular section. If PSYS_SRC_PATTERN_ANGLE_CONE or PSYS_SRC_PATTERN_ANGLE_CONE_EMPTY is used, the presentation is a 3D spherical section. Note that the value of this parameter and PSYS_SRC_ANGLE_BEGIN are internally re-ordered such that this parameter gets the larger of the two values. | 23 | |
| float | DEPRECATED: Use PSYS_SRC_ANGLE_BEGIN instead. Works similar to its replacement rule, except the edge of the section is aligned with the emitter facing, rather than its center. | 10 | ||
| float | DEPRECATED: Use PSYS_SRC_ANGLE_END instead. Works similar to its replacement rule, except the edge of the section is aligned with the emitter facing, rather than the section's center. | 11 | ||
| PSYS_SRC_TARGET_KEY | key | Specifies the key of a target object, prim, or agent towards which the particles will change course and move. They will attempt to end up at the geometric center of the target at the end of their lifetime. Requires the PSYS_PART_TARGET_POS_MASK flag be set. caveat 4 | 20 | |
| Particle Appearance | ||||
| PSYS_PART_START_COLOR | vector | A vector specifying the color of the particles upon emission. | 1 | |
| PSYS_PART_END_COLOR | vector | A vector specifying the color the particles transition to during their lifetime. Only used if the PSYS_PART_INTERP_COLOR_MASK flag is set. | 3 | |
| PSYS_PART_START_ALPHA | float | Specifies the alpha of the particles upon emission. Valid values are in the range 0.0 to 1.0. Lower values are more transparent; higher ones are more opaque. | 2 | |
| PSYS_PART_END_ALPHA | float | Specifies the alpha the particles transition to during their lifetime. Only used if the PSYS_PART_INTERP_COLOR_MASK flag is set. Valid values are the same as PSYS_PART_START_ALPHA. | 4 | |
| PSYS_PART_START_SCALE | vector | Specifies the scale or size of the particles upon emission. Valid values for each direction are 0.04 (0.03125) to 4.0, in meters. Since particles are essentially 2D sprites, the Z component of the vector is ignored and can be set to 0.0. | 5 | |
| PSYS_PART_END_SCALE | vector | Specifies the scale or size the particles transition to during their lifetime. Only used if the PSYS_PART_INTERP_SCALE_MASK flag is set. Valid values are the same as PSYS_PART_START_SCALE. | 6 | |
| PSYS_SRC_TEXTURE | string | Specifies the name of a texture in the prim's inventory to use for each particle. Alternatively, you may specify an asset key UUID for a texture. | 12 | |
| Particle Flow | ||||
| PSYS_SRC_MAX_AGE | float | Specifies the length of time, in seconds, that the emitter will operate upon coming into view range (if the particle system is already set) or upon execution of this function (if already in view range). Upon expiration, no more particles will be emitted, except as specified above. Zero will give the particle system an infinite duration. (caveat 1) | 19 | |
| PSYS_PART_MAX_AGE | float | Specifies the lifetime of each particle emitted, in seconds. Maximum is 30.0 seconds. During this time, the particle will appear, change appearance and move according to the parameters specified in the other sections, and then disappear. | 7 | |
| PSYS_SRC_BURST_RATE | float | Specifies the time interval, in seconds, between "bursts" of particles being emitted. Specifying a value of 0.0 will cause the emission of particles as fast as the viewer can do so. | 13 | |
| PSYS_SRC_BURST_PART_COUNT | integer | Specifies the number of particles emitted in each "burst". | 15 | |
| Particle Motion | ||||
| PSYS_SRC_ACCEL | vector | Specifies a directional acceleration vector applied to each particle as it is emitted, in meters per second. Valid values are 0.0 to 100.0 for each direction, as region coordinates. | 8 | |
| PSYS_SRC_OMEGA | vector | Specifies the rotational spin of the emitter in radians per second along each axis. This "unsticks" the emitter facing from the prim's positive Z axis and is noticeable in directional presentations. Prim spin (via llTargetOmega) has no effect on emitter spin. (caveat 2 and caveat 3) | 21 | |
| PSYS_SRC_BURST_SPEED_MIN | float | Specifies the minimum value of a random range of values which is selected for each particle in a burst as its initial speed upon emission, in meters per second. Note that the value of this parameter and PSYS_SRC_BURST_SPEED_MAX are internally re-ordered such that this parameter gets the smaller of the two values. | 17 | |
| PSYS_SRC_BURST_SPEED_MAX | float | Specifies the maximum value of a random range of values which is selected for each particle in a burst as its initial speed upon emission, in meters per second. Note that the value of this parameter and PSYS_SRC_BURST_SPEED_MIN are internally re-ordered such that this parameter gets the larger of the two values. | 18 | |
| LL_PART_* constants are only found in viewer - indra/llmessage/llpartdata.h , those flags in red have been commented out. | ||||
Caveats
- When using particle systems that have a non-zero emitter age (PSYS_SRC_MAX_AGE) setting, you may notice that the particle system may restart without any scripted trigger going off. This is due to a bug which causes the emitter to "reset" when any of the prim properties are updated or otherwise sent to the viewer. As a result, you may have to use a timer or a forced sleep and then clear the particle system once the age has expired. Debbie Trilling has posted a work-around here: http://forums.secondlife.com/showpost.php?p=1996465&postcount=6
- The spin defined by PSYS_SRC_OMEGA is relative to the region coordinate system, NOT the prim's local coordinate system.
- When freshly created a prims emitter is set to ZERO_ROTATION within the prim. If whilst designing a particle display you use PSYS_SRC_OMEGA the emitter will be rotated. If then you change the PSYS_SRC_OMEGA vector the emitter will not be reset to ZERO_ROTATION but will remain rotated to whatever axis it was at when stopped or altered. This can result in particles being displayed quite differently in the corrupted prim than they would be using the same script in a fresh prim (with a fresh emitter).
- Particles moving towards a humanoid avatar, specified by PSYS_SRC_TARGET_KEY rule and setting the PSYS_PART_TARGET_POS_MASK flag, will end up at the geometric center of the avatar's bounding box which, unfortunately, make them appear to be striking the person in the groin area. If you want them to end up at another point on a target avatar, you instead have to place a target prim that is moved to the position where you wish them to end up, and use the key of that prim for the value of the PSYS_SRC_TARGET_KEY rule.
- The Second Life viewer uses optimizations in culling objects which are too small to see at certain distances. If your emitter is very small, and is culled due to distance, the particle system associated with it will not be rendered either.
Examples
This example produces an effusion of glowing red spheres:
<lsl>llParticleSystem( [
Useful Snippets
Useful functions for storing/retrieving color and alpha values to/from integers:
<lsl>integer ColorAlphatoRGBA(vector color, float alpha) {
return (((integer)(alpha * 255.0) & 0xFF) << 24)
Notes
- The default particle count for the client is normally set at 4096. That is the max particle count the client will render for ALL active particle systems within view range. Good particle system design is key to avoid "spamming" everyone with your particles, and starving out other people's particle systems. As such, if you are experiencing trouble getting your particle emitter to emit as many particles as you like, it may be the victim of particle starvation. Client/viewer lag (low frame rates) can also cause this issue, as particles are a rather low priority for rendering. The best solution for this is to move to a less laggy environment relatively free of other particle systems when designing and testing your own.
- Once particles are emitted, their direction of motion can only be affected by PSYS_SRC_ACCEL, the PSYS_PART_TARGET_POS_MASK flag, or the PSYS_PART_FOLLOW_SRC_MASK flag. As such, there is no good way to create the "swirling vortex" effect (like the one used in the viewer to indicate an object talking, begin derezzed, or when an avatar leaves the sim/grid). The effect can be created with a moving particle source (E.G. An orbiting script.)
See Also
Articles
| • | Color in LSL | |||
| • | Translucent Color |
Deep Notes
Missing 14
There is a missing constant which would have the value 14, the underlying enumeration LLPSScriptFlags has that as LLPS_SRC_BURST_DURATION, the value is used nowhere else in the client source. This isn't surprising considering that the burst duration is dependent on the PSYS_SRC_BURST_PART_COUNT, PSYS_SRC_BURST_RATE.
Signature |
|---|
function void llParticleSystem( list rules ); |