code: function( accuIndex ) {
  
  		var stride = this.valueSize,
  			buffer = this.buffer,
  			offset = accuIndex * stride + stride,
  
  			weight = this.cumulativeWeight,
  
  			binding = this.binding;
  
  		this.cumulativeWeight = 0;
  
  		if ( weight < 1 ) {
  
  			// accuN := accuN + original * ( 1 - cumulativeWeight )
  
  			var originalValueOffset = stride * 3;
  
  			this._mixBufferRegion(
  					buffer, offset, originalValueOffset, 1 - weight, stride );
  
  		}
  
  		for ( var i = stride, e = stride + stride; i !== e; ++ i ) {
  
  			if ( buffer[ i ] !== buffer[ i + stride ] ) {
  
  				// value has changed -> update scene graph
  
  				binding.setValue( buffer, offset );
  				break;
  
  			}
  
  		}
  
  	}
docs: apply the state of 'accu<i>' to the binding when accus differ