FlowField.pyde

# Python Flowfield example
# Doug Goodwin
# Example derived from Daniel Shiffman's "Nature of Code"
# http:#natureofcode.com

# Flow Field Following

class FlowField(object):
    def __init__(self,r):
        # A flow field is a two dimensional array of PVectors
        # How large is each "cell" of the flow field
        self.resolution = r
        # Determine the number of columns and rows based on sketch's width and height
        self.cols = width/self.resolution
        self.rows = height/self.resolution
        # initialize a 2 dimensional matrix of cols x rows
        self.field = [[0 for x in range(0,self.rows)] for y in range(0,self.cols)]
        # now you can do this: self.field[0][0] = 1
        # Reseed noise so we get a new flow field every time
        noiseSeed( int(random(10000)) )
        xoff = 0
        
        for i in range(0,self.cols):
            yoff = 0
            for j in range(0,self.rows):
                print("i,j:",i,j)
                theta = map( noise(xoff,yoff),0,1,0,TWO_PI )
                # Polar to cartesian coordinate transformation 
                # to get the x and y components of the vector
                self.field[i][j] = PVector( cos(theta),sin(theta) )
                yoff += 0.1
            xoff += 0.1
    
    

    # Renders a vector object 'v' as an arrow and a position 'x,y'
    def drawVector(self,v, x, y, scayl):
        pushMatrix()
        arrowsize = 4
        # Translate to position to render vector
        translate(x,y)
        stroke(0,100)
        # Call vector heading function to get direction 
        # (note that pointing to the right is a heading of 0) and rotate
        rotate(v.heading2D())
        # Calculate length of vector & scale it to be bigger or smaller if necessary
        len = v.mag()*scayl
        # Draw three lines to make an arrow 
        # (draw pointing up since we've rotate to the proper direction)
        line(0,0,len,0)
        # vector arrows
        line(len,0,len-arrowsize,+arrowsize/2)
        line(len,0,len-arrowsize,-arrowsize/2)
        popMatrix()

    def lookup(self,lookup):
        column = int(constrain(self.lookup.x/self.resolution,0,self.cols-1));
        row = int(constrain(self.lookup.y/self.resolution,0,self.rows-1));
        return self.field[column][row].get()

    # Draw every vector
    def display(self):
        for i in range(0,self.cols):
            for j in range(0,self.rows):
                self.drawVector(self.field[i][j],i*self.resolution,j*self.resolution,self.resolution);


size(900, 600)
# Make a new flow field with "resolution" of 16
f = FlowField(16)
f.display()