Patch to squarefeet/ShaderParticleEngine adding 'spiral' emitter type

ShaderParticles.js.diff

134a135,188
>     /**
>      * Create a new THREE.Vector3 instance and project it onto a random point
>      * on a spiral (in the XY-plane) centered at `base` and with randomized radius.
>      *
>      * Spiral generated by rotating series of ellipses generated with the
>      * specified skew in accordance with the density wave theory
>      *
>      * @param  {THREE.Vector3} base
>      * @param  {Number} radius
>      * @param  {THREE.Vector3} radiusSpread
>      * @param  {THREE.Vector3} radiusScale
>      * @param  {Number} radiusSpreadClamp
>      * @param  {Number} radiusMax
>      * @param  {Number} skew
>      *
>      * @private
>      *
>      * @return {THREE.Vector3}
>      */
>     randomVector3OnSpiral: function( base, radius, radiusSpread, radiusScale, radiusSpreadClamp, radiusMax, skew ) {
>         /// generate vertex in same manner as disk...
>         var t = 6.2832 * Math.random();
>         var rand = this._randomFloat( radius, radiusSpread );
> 
>         if( radiusSpreadClamp ) {
>             rand = Math.round( rand / radiusSpreadClamp ) * radiusSpreadClamp;
>         }
> 
>         var p = rand / radiusMax;
> 
>         // ...except w/ skew applied to form ellipse
>         var vec = new THREE.Vector3( Math.cos(t), Math.sin(t) * skew, 0 );
> 
>         // rotate ellipse by percentage total distance it is in total spiral,
>         //  we could parameterize this to determine the number of rotations
>         //  that formal the spiral, determining the # of arms
>         var angle = 6.2832 * p;
>         vec.applyAxisAngle(new THREE.Vector3(0,0,1), angle);
> 
>         /// from here it's the same as disk
>         vec.multiplyScalar( rand );
> 
>         if ( radiusScale ) {
>             vec.multiply( radiusScale );
>         }
> 
>         /// particles near the center have greater z values forming center
>         vec.z = (Math.random() - 0.5 ) * Math.pow(0.975, vec.length()) * 10;
> 
>         vec.add( base );
> 
>         return vec ;
>     },
> 
162a217,247
>     /**
>      * Create a new THREE.Vector3 instance, and given a spiral w/ a specified radius and
>      * point `position` on spiral, set direction towards sphere center with tangential
>      * component and random magnitude
>      *
>      * @param  {THREE.Vector3} base
>      * @param  {THREE.Vector3} position
>      * @param  {Number} speed
>      * @param  {Number} speedSpread
>      * @param  {Number} radiusMax
>      *
>      * @private
>      *
>      * @return {THREE.Vector3}
>      */
>     randomVelocityVector3OnSpiral: function( base, position, speed, speedSpread, radiusMax ){
>         var direction = new THREE.Vector3().subVectors( base, position );
> 
>         /// speed scales according to distance
>         var d = direction.length();
>         var p = d / radiusMax;
> 
>         direction.normalize()
>                   .multiplyScalar( Math.abs( this._randomFloat( speed / p, speedSpread ) ) )
>                   .negate();
>         direction.add(direction.cross(new THREE.Vector3(0,0,-1)).multiplyScalar(p));
> 
>         return direction;
>     },
> 
> 
270a356,400
>     /**
>      * Given an existing particle vector, project it onto a random point
>      * on a spiral (in the XY-plane) centered at `base` and with randomized radius.
>      *
>      * @private
>      *
>      * @param  {THREE.Vector3} v
>      * @param  {THREE.Vector3} base
>      * @param  {Number} radius
>      * @param  {THREE.Vector3} radiusSpread
>      * @param  {THREE.Vector3} radiusScale
>      * @param  {Number} radiusSpreadClamp
>      * @param  {Number} radiusMax
>      * @param  {Number} skew
>      */
>     randomizeExistingVector3OnSpiral: function( v, base, radius, radiusSpread, radiusScale, radiusSpreadClamp, radiusMax, skew ) {
>         var rand = Math.random,
>             t = 6.2832 * rand(),
>             rand = Math.abs( this._randomFloat( radius, radiusSpread ) );
> 
>         if( radiusSpreadClamp ) {
>             rand = Math.round( rand / radiusSpreadClamp ) * radiusSpreadClamp;
>         }
> 
>         var p = rand / radiusMax;
> 
>         v.set(
>             Math.cos( t ),
>             Math.sin( t ) * skew,
>             0
>         );
> 
>         var angle = 6.2832 * p;
>         v.applyAxisAngle(new THREE.Vector3(0,0,1), angle);
>         v.multiplyScalar( rand );
> 
>         if ( radiusScale ) {
>             v.multiply( radiusScale );
>         }
> 
>         v.z = (Math.random() - 0.5 ) * Math.pow(0.975, v.length()) * 10;
> 
>         v.add( base );
>     },
> 
277a408,423
>     randomizeExistingVelocityVector3OnSpiral: function( v, base, position, speed, speedSpread, radiusMax ) {
>         v.copy(position).sub(base);
> 
>         /// speed scales according to distance
>         var d = v.length();
>         var p = d / radiusMax;
> 
>         /// velocity component towards center of spiral
>         v.normalize()
>          .multiplyScalar( Math.abs( this._randomFloat( speed / p, speedSpread ) ) )
>          .negate();
> 
>         /// tangential velocity component (again scale w/ distance)
>         v.add(v.cross(new THREE.Vector3(0,0,-1)).multiplyScalar(p));
>     },
> 
312a459
>     that.fadeFactor             = parseFloat( typeof options.fadeFactor === 'number' ? options.fadeFactor : 0.0 );
325a473
>         fadeFactor:     { type: 'f',    value: that.fadeFactor },
463,464c611,615
<             }
<             else {
---
>             }else if(emitter.type === 'spiral'){
>                 vertices[i]         = that._randomVector3OnSpiral( emitter.position, emitter.radius, emitter.radiusSpread, emitter.radiusScale, emitter.radiusSpreadClamp, emitter.radiusMax, emitter.skew );
>                 velocity[i]         = that._randomVelocityVector3OnSpiral( vertices[i], emitter.position, emitter.speed, emitter.speedSpread, emitter.radiusMax );
> 
>             }else {
707a859
>         'uniform float fadeFactor;',
710d861
< 
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>                 /// optional fade w/ distance
>                 'if( fadeFactor != 0.0 ) {',
>                   'vColor = mix( vColor, vec4(0.0, 0.0, 0.0, 0.0), 1.0 / length ( pos.xyz ) * fadeFactor );',
>                 '}',
> 
852c1008
<     that.type                   = (options.type === 'cube' || options.type === 'sphere' || options.type === 'disk') ? options.type : 'cube';
---
>     that.type                   = (options.type === 'cube' || options.type === 'sphere' || options.type === 'disk' || options.type == 'spiral') ? options.type : 'cube';
857c1013
<     // These two properties are only used when this.type === 'sphere' or 'disk'
---
>     // These properties are only used when this.type === 'sphere', 'disk', or 'spiral'
861a1018
>     that.radiusMax              = that.radius + that.radiusSpread;
869,870c1026
< 
<     // And again here; only used when this.type === 'sphere' or 'disk'
---
>     // And again here; only used when this.type === 'sphere', 'disk', or 'spiral'
873a1030,1032
>     /// These properties are only used when this.type === 'spiral'
>     that.skew                   = parseFloat( typeof options.skew === 'number' ? options.skew : 1.0 );
> 
943c1102,1103
<             ( type === 'disk' && that.radius === 0 )
---
>             ( type === 'disk' && that.radius === 0 ) ||
>             ( type === 'spiral' && that.radius === 0 )
967a1128,1132
>         }
> 
>         else if( type === 'spiral') {
>             that._randomizeExistingVector3OnSpiral( particlePosition, that.position, that.radius, that.radiusSpread, that.radiusScale, that.radiusSpreadClamp, that.radiusMax, that.skew );
>             that._randomizeExistingVelocityVector3OnSpiral( particleVelocity, that.position, particlePosition, that.speed, that.speedSpread, that.radiusMax );