Template:LSL Function/ParticleSystem

spec

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., {{{1}}}; ) 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.

caveats

1. 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
2. The spin defined by PSYS_SRC_OMEGA is relative to the region coordinate system, NOT the prim's local coordinate system.
3. 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).
4. 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.
5. 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.

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.)

helpers

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)

constants_nb

	Rule / Value Constant	Value 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
	PSYS_PART_BEAM_MASK		(unimplemented) mask but in the enum	0x200
	LL_PART_HUD		Used by the viewer to keep HUD and World particle sources separate.	0x40000000
	LL_PART_DEAD_MASK		Removes particles, not compatible with any other PSYS_PART_*_MASK	0x80000000
	LL_PART_RANDOM_ACCEL_MASK		(unimplemented & commented out) Presumed to be used to apply random acceleration to the particles.	-
	LL_PART_RANDOM_VEL_MASK		(unimplemented & commented out) Presumed to be used to specify random velocity for the particles upon emission.	-
	LL_PART_TRAIL_MASK		(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_EXPLODE		Sprays particles outwards in a spherical area. The Initial velocity of each particle is determined by PSYS_SRC_BURST_SPEED_MIN and PSYS_SRC_BURST_SPEED_MAX. The EXPLODE pattern ignores the ANGLE parameters.	0x02
	PSYS_SRC_PATTERN_ANGLE_CONE		Sprays particles outwards in a spherical, sub-spherical, conical or ring shaped area, as defined by the ANGLE parameters PSYS_SRC_ANGLE_BEGIN and PSYS_SRC_ANGLE_END. The ANGLE_CONE pattern can be used to imitate the EXPLODE pattern by explicitly setting PSYS_SRC_ANGLE_BEGIN to 0.00000 and PSYS_SRC_ANGLE_END to 3.14159 (or PI) (or vice versa).	0x08
	PSYS_SRC_PATTERN_ANGLE		Sprays particles outward in a flat circular, semi-circular, arc or ray shaped areas, as defined by PSYS_SRC_ANGLE_BEGIN and PSYS_SRC_ANGLE_END. The circular pattern radiates outwards around the prim's local X axis line.	0x04
	PSYS_SRC_PATTERN_DROP		Creates particles with no initial velocity. The DROP pattern will overrides any values given for PSYS_SRC_BURST_RADIUS, PSYS_SRC_BURST_SPEED_MIN, and PSYS_SRC_BURST_SPEED_MAX, setting each to 0.00000. (All patterns will behave like the DROP pattern, if RADIUS, SPEED_MIN and SPEED_MAX are explicitly set to 0.0000.)	0x01
	PSYS_SRC_PATTERN_ANGLE_CONE_EMPTY		(incomplete implementation) acts the same as the PSYS_SRC_PATTERN_DROP pattern, it is believed that the original intention for this pattern was to invert the effect of the ANGLE parameters, making them delineate an area where particles were NOT to be sprayed. (effectively the inverse or opposite of the behavior of the ANGLE_CONE pattern).	0x10
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-archive.secondlife.com/327/f5/226722/1.html 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
PSYS_SRC_INNERANGLE		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
PSYS_SRC_OUTERANGLE		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.

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.