Grasshopper Boids Example

gistfile1.py

from Rhino.Geometry import Point3d, Vector3d, Curve

# inputs
    # numBoids
    # switch
    # boundingBox

class Boid():
    
    radius = 5.0
    
    def __init__(self, initialPosition, initialHeading):
        self.position = initialPosition
        self.heading = initialHeading
        self.trail = [initialPosition]
    
    def move(self):
        """Updates boid position based on heading."""
        self.position = Point3d.Add( self.position, self.heading )
        self.trail.append( self.position )
    
    def findDirection(self, allBoids):
        """Filters self out of others and
        Updates heading based on other boids."""
        others = allBoids[:]
        others.remove(self)
        neighbors = []
        for other in others:
            distance = self.position.DistanceTo( other.position )
            if distance < self.radius:
                neighbors.append(other)
        if neighbors:
            self.align(neighbors)
            self.cohere(neighbors)
 
    def align(self, others):
        headings = [other.heading for other in others]
        uberVector = Vector3d(0.0,0.0,0.0)
        for heading in headings:
            uberVector = Vector3d.Add( uberVector, heading )
        self.heading = Vector3d.Divide( uberVector, uberVector.Length )
        
    def cohere(self, others):
        centerPoint = others.pop(0).position
        for other in others:
            centerPoint = Point3d.Add( centerPoint, other.position )
        centerPoint = Point3d.Divide( centerPoint, len(others) - 1 )
        direction = Point3d.Subtract( centerPoint, self.position )
        direction = Vector3d.Divide( direction, direction.Length )
        self.heading = Vector3d.Add( direction, self.heading )

boids = []
if initialPoints:
    # initial state
    # create random points
    for point in initialPoints:
        heading = Vector3d( Point3d.Multiply( point, -1 ) )
        boid = Boid( point, heading )
        boids.append( boid )
        
if switch and numSteps:
    print 'go boids!'
    # for loop
    for i in range(int(numSteps)):
    
        # evaluate boids
        for boid in boids:
            boid.findDirection( boids )
        
        # move boids
        for boid in boids:
            boid.move()
trails = []
for boid in boids:
    trails.append(Curve.CreateControlPointCurve( boid.trail, 3))
points = [boid.position for boid in boids]