Helix Pattern with FOR Loops

Overview

This session explores function definitions and mathematical functions to create visually striking 3D patterns. By combining math.sin() for Z-axis oscillation with incremental Y positioning and world-space pivot rotation, you'll generate a helix of 500 spheres spiraling around the scene origin. The session also covers variable scope and how parameters pass data into functions.

Key Concepts

• Function definitions — using def to create reusable functions with parameters
• math.sin() — generating oscillating values between -1 and 1 for wave-like motion
• World-space pivots — setting the pivot to the origin with pm.xform() to rotate objects around a central point
• Iteration scaling — dividing or multiplying the loop counter to control spacing and rotation speed
• Variable scope — understanding that variables defined inside a function are local to that function

Code

This script defines a function that creates a sphere, positions it using sine-wave oscillation, and rotates it around the world origin to form a helix.

"""
#############################################################################
filename    session_4a_code_commented.py
author      Matt Osbond
course      CS115
Brief Description:
    Session 4A - Tuesday Jan 28th
    Using a FOR loop and some math to create a helix effect
#############################################################################
"""

import pymel.core as pm
import math

def create_ball(iter, size):
    """This is a function DEFINITION, as indicated by the "def" keyword.
    The parentheses that follow the name of the function are called the parameters.
    These are variables that will be defined elsewhere, where the function is called from.
    """
    # Create a ball, remembering to return the first element (element 0) of the list returned by "polySphere"
    ball = pm.polySphere(radius=size/2)[0]

    # Here we begin to make the position in Z vary with each iteration, by using the "sin" math function
    # This returns a value that will fluctuate between 1 and -1
    # As this is such a small variation in the Maya scene, we multiply by 10 to exaggerate the effect
    z_pos = math.sin(iter) * 10

    # Each step, we want to move the ball higher up in Y
    # But, if we add 1 each time (use the iteration of the FOR loop) then it will go up too fast
    # and the balls will be too spread out
    # So we opt to divide this by 10
    y_pos = iter/10

    # Move the ball to the new location
    pm.move(ball, [0, y_pos, z_pos])

    # We now want to rotate the ball around the scene origin
    # To do this, set the world space pivot to [0,0,0]
    pm.xform(worldSpace=True, piv=[0, 0, 0])

    # Calculate the y rotation, by first assigning it to be iter, then choosing to
    # speed it up or slow it down (increasing the multiplier will make it rotate faster)
    y_rot = iter * 1.5

    # Rotate around Y axis
    pm.rotate([0, y_rot, 0])

# Create 500 balls
for i in xrange(0, 500):
    create_ball(i, 5)