Trees are a very common sight in Second Life. Some trees drop a stream of leaves to give a fall effect. This recipe will show how to create a leaf generator. The leaf generator can be seen in Figure 4.3.

Figure 4.3: Fall Leafs

    The leaf generator was based on the basic particle script seen in Recipe 4.1. To learn more about the values that can be specified for a particle emitter, refer to Recipe 4.1. The script for the leaf particle emitter can be seen in Listing 4.3.

Listing 4.3: Fall Leafs (Leafs.lsl)

// From the book:
//
// Scripting Recipes for Second Life
// by Jeff Heaton (Encog Dod in SL)
// ISBN: 160439000X
// Copyright 2007 by Heaton Research, Inc.
//
// This script may be freely copied and modified so long as this header
// remains unmodified.
//
// For more information about this book visit the following web site:
//
// http://www.heatonresearch.com/articles/series/22/

generalParticleEmitterOn()                
{   
    llParticleSystem([                   
        PSYS_PART_FLAGS , 0 
    //| PSYS_PART_BOUNCE_MASK       //Bounce on object's z-axis
    | PSYS_PART_WIND_MASK           //Particles are moved by wind
    | PSYS_PART_INTERP_COLOR_MASK   //Colors fade from start to end
    | PSYS_PART_INTERP_SCALE_MASK   //Scale fades from beginning to end
    | PSYS_PART_FOLLOW_SRC_MASK     //Particles follow the emitter
    | PSYS_PART_FOLLOW_VELOCITY_MASK//Particles are created at the velocity of the emitter
    //| PSYS_PART_TARGET_POS_MASK   //Particles follow the target
    | PSYS_PART_EMISSIVE_MASK       //Particles are self-lit (glow)
    //| PSYS_PART_TARGET_LINEAR_MASK//Undocumented--Sends particles in straight line?
    ,
    
    //PSYS_SRC_TARGET_KEY , NULL_KEY,//The particles will head towards the specified key
    //Select one of the following for a pattern:
    //PSYS_SRC_PATTERN_DROP                 Particles start at emitter with no velocity
    //PSYS_SRC_PATTERN_EXPLODE              Particles explode from the emitter
    //PSYS_SRC_PATTERN_ANGLE                Particles are emitted in a 2-D angle
    //PSYS_SRC_PATTERN_ANGLE_CONE           Particles are emitted in a 3-D cone
    //PSYS_SRC_PATTERN_ANGLE_CONE_EMPTY     Particles are emitted everywhere except for a 3-D cone
    
    PSYS_SRC_PATTERN,           PSYS_SRC_PATTERN_ANGLE_CONE
    
    ,PSYS_SRC_TEXTURE,           "leaf"           //UUID of the desired particle texture, or inventory name
    ,PSYS_SRC_MAX_AGE,           0.0            //Time, in seconds, for particles to be emitted. 0 = forever
    ,PSYS_PART_MAX_AGE,          10.0            //Lifetime, in seconds, that a particle lasts
    ,PSYS_SRC_BURST_RATE,        0.5            //How long, in seconds, between each emission
    ,PSYS_SRC_BURST_PART_COUNT,  6              //Number of particles per emission
    ,PSYS_SRC_BURST_RADIUS,      10.0           //Radius of emission
    ,PSYS_SRC_BURST_SPEED_MIN,   0.1             //Minimum speed of an emitted particle
    ,PSYS_SRC_BURST_SPEED_MAX,   0.5             //Maximum speed of an emitted particle
    ,PSYS_SRC_ACCEL,             <0,0,0>    //Acceleration of particles each second
    ,PSYS_PART_START_COLOR,      <1,1,1>  //Starting RGB color
    ,PSYS_PART_END_COLOR,        <0,0,0>  //Ending RGB color, if INTERP_COLOR_MASK is on 
    ,PSYS_PART_START_ALPHA,      1.0            //Starting transparency, 1 is opaque, 0 is transparent.
    ,PSYS_PART_END_ALPHA,        1.0            //Ending transparency
    ,PSYS_PART_START_SCALE,      <.25,.25,.25>  //Starting particle size
    ,PSYS_PART_END_SCALE,        <.25,.25,.25>  //Ending particle size, if INTERP_SCALE_MASK is on
    ,PSYS_SRC_ANGLE_BEGIN,       90 * DEG_TO_RAD //Inner angle for ANGLE patterns
    ,PSYS_SRC_ANGLE_END,         90 * DEG_TO_RAD//Outer angle for ANGLE patterns
    ,PSYS_SRC_OMEGA,             <0.0,0.0,0.0>  //Rotation of ANGLE patterns, similar to llTargetOmega()
            ]);
}

generalParticleEmitterOff()
{
    llParticleSystem([]);
}

default
{    
    state_entry()
    {
        generalParticleEmitterOn();
    }

    touch_start( integer num )            
    {
        // uncomment the following line to allow this effect to be turned off
        //state off;        
    }
}

state off
{
    state_entry()
    {
        generalParticleEmitterOff();
    }
    
    touch_start( integer num )        
    {
        state default;
    }
}

    Unlike the basic particle script, the leaf emitter script uses a texture. This texture, named “leaf” is an image of a fall leaf. It is located in the object inventory of the leaf emitter. This allows the particles to appear as leaves.

    To produce the leaves a PSYS_PART_MAX_AGE of 10 seconds is specified. The leaves disappear relatively slowly as they travel. The PSYS_SRC_BURST_RATE and PSYS_SRC_BURST_PART_COUNT specify the creation of six new leafs every half a second.

    The PSYS_SRC_BURST_SPEED_MIN and PSYS_SRC_BURST_SPEED_MAX of .1 and .5 cause the leaves to travel relatively slowly. The PSYS_SRC_ANGLE_BEGIN and PSYS_SRC_ANGLE_END specify that the leaves will be emitted at 90 degrees.