VPython 3D Objects

Claimed by Do Won Kim (Fall 2017)

The main purpose of the VPython programming language is to create 3D simulation with creating the 3D objects. To achieve this purpose, VPython already contains a number of built-in 3-dimensional objects, and these objects are displayed in a 3D graphics module called Visual. Familiarizing with these objects is important for lab coding.

Before start coding, make sure to have

from __future__ import division
from visual import *

on the top of your script.

This document is written based on VPython 7.

List of 3D Objects

Image of Each Objects

VPython is packaged with a variety of 3-Dimensional objects. By clicking each names of the objects, you can go to the official description of each objects from Glowscript. The objects are listed in alphabetical order.

Arrow

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Example arrow

Box

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Example box

Cone

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Example cone

Curve

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Example curve

Cylinder

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Example cylinder

Ellipsoid

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Example ellipsoid

Extrusion

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Example extrusion

Helix

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Example helix

Label

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Example label

Points

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Example points

Pyramid

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Example pyramid

Ring

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Example ring

Sphere

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Example sphere

Text

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Example text

Example Code of Each Objects

Arrow

a = arrow(pos=(0,2,1),axis=(5,0,0), color = color.red)

Box

b = box(pos=(0,0,0),length=3, height=3, width=3, color = color.orange)

Cone

c = cone(pos=(0,0,0),axis=vector(2,0,0), radius=1, color = color.yellow)

Curve

c = curve(pos=[(-1,-1,0), (1,-1,0)], color = color.green) #create object
c.append(pos=(3,2,-2)) #append next position vector
c.append(pos=(4,1,2))

Cylinder

c = cylinder(pos=vector(0,2,1), axis=vector(5,0,0), radius=1, color=color.cyan)

Ellipsoid

e = ellipsoid(pos=vector(0,0,0), length=3, height=5, width=7, color=color.blue)

Extrusion

#define polygons first
tri = Polygon( [(-2,0), (0,4), (2,0)] )
circ = shapes.circle(pos=(0,1.5), radius=0.8)
straight = [(0,0,0),(0,0,-4)]
#create extrusion
e = extrusion(pos=straight, shape=tri-circ, color=color.magenta)

Helix

h = helix(pos=vector(0,2,1), axis=vector(5,0,0), radius=0.5, color=(0.96,0.73,0.14))

Label

l = label(pos=vector(0,0.25,0), text='This is a Label', xoffset=20, yoffset=50, space=30, height=16, border=4,font='sans')

Points

p = points(pos=[vector(-1,0,0), vector(1,0,0)], radius=50, color=(1,1,.94))

Pyramid

p = pyramid(pos=vector(5,2,0), size=vector(3,3,2), color=(0.82, 0.41, 0.12))

Ring

r = ring(pos=vector(1,1,1), axis=vector(0,1,0),radius=0.5, thickness=0.1, color=(0.14, 1, 0.83))

Sphere

s = sphere(pos=vector(1,1,1), radius=5, color=(0.5, 1, 0.5))

Text

t = text(text='This is \ntext', #use \n for changing line
    align='center', color=(0.94, 0.90, 0.55))

Commonly Used Objects

The following objects are often used in class lab.

Sphere

The sphere object can be used to represent a wide variety of things, but it is mostly used to represent spherical objects such as planets or particles such as protons and electrons. Two things must be set; the position (vector), and the radius (numerical value).

Arrow

The arrow is perhaps the most important object for physics simulation. It can be used to represent various forces as well as visualizing vectors. To create an arrow, the position (vector), axis (vector), and the shaftwidth (a numerical value) must be set.

Curve

The curve is often used to create a trail mark that represents a path that the object has moved, and it is also frequently used to create graphs. To create a curve, put the initial position vector of the curve, and append the next positions while updating the position in the while loop.

Object Application

Following code is an example usage and application of object creation for lab simulations.

## objects
ceiling = box(pos=vector(0,0,0), size = vector(0.2, 0.01, 0.2))         ## origin is at ceiling
ball = sphere(pos=vector(.1,-.2,.3), radius=0.025, color=color.orange) ## note: spring initially compressed
spring = helix(pos=ceiling.pos, color=color.cyan, thickness=.003, coils=40, radius=0.015) ## change the color to be your spring color
parrow = arrow(color=color.magenta, pos=ball.pos, axis=vector(0,0,0))
farrow = arrow(color=color.red, pos=ball.pos, axis=vector(0,0,0))
trail = curve(color=ball.color)

#graphs
Kgraph=gcurve(color=color.red)
Ugraph=gcurve(color=color.cyan)
KUgraph=gcurve(color=color.yellow)

#graph updates are done in the while loop.

See also

1. VPython Basics
2. VPython
3. VPython Animation
4. VPython Objects

Further reading

1. 3D object details
2. VPython Information

References

http://www.glowscript.org/docs/VPythonDocs/primitives.html

http://vpython.org/contents/docs/shapes.html

http://vpython.org/