On Tue, Sep 22, 2009 at 12:41 PM, Jason Grout
<jason-s...@creativetrax.com> wrote:
> Since we also already have momentum for incorporating mayavi, we should
> also point out the mayavi tvtk "visual" module, whose api is modeled
> after vpython:
>
> https://svn.enthought.com/enthought/wiki/TVTKIntroduction#visual
>
> I've used vpython too, and I thought it was really nice and simple.
Prabhu may comment with more information, but in the meantime, it's
worth keeping in mind that 'tvisual' has significantly lower
performance than visual, and in this case I'm not sure it can be
fixed. The issue is that the traits event handling machinery proves
to be too much overhead when you're trying to render a 3d scene at
interactive framerates, and the geometry is already being computed by
a python loop. Since tvtk is based on traits, all the traits machinery
is still active and in this case may be a bit too much.
If memory serves me right, Prabhu wasn't super optimistic about being
able to match vpython performance with tvisual, but I could (and would
love to) be misremembering, or perhaps it's just a matter of putting
manpower into it and not a fundamental limitation.
I just mention it so you are aware that out of the box, tvisual's
performance is just not enough to be usable like vpython is (and I
only tested it on fairly simple examples).
In case you'd like to run a simple comparison (and perhaps things have
improved), I'm attaching a simple example of parabolic motion written
both for vpython (old version) and tvtk/visual. Caveat: I haven't run
this code in years, so I'm not sure it runs with today's vpython or
tvtk.
Cheers,
f
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#!/usr/bin/env python
"""Visual Python demo: shooting a falling object.
Note that this script can NOT be run inside ipython via the 'run' command.
You MUST run it from the command line as a standalone program. Start by doing
chmod +x shoot.py
(or whatever you called it), and then you can run it via
./shoot.py
"""
import time
import sys
# Visual is built on top of the 'old' Numeric, so do NOT use numpy here. We
# do a wholesale import for coding convenience, this is highly discouraged in
# larger codebases (but usually OK in very small demo scripts and interactive
# use).
from Numeric import *
import visual as V
# Geometric parameters (all in MKS units)
theta = pi/4 # initial angle of gun
D = 20 # width ...
H = 20 # height of floor
g = -9.8 # gravity
gun_len = 2 # size of gun
arrow_len = 4 # and of arrow
v0_default = 15 # default for initial velocity if not given
# Numerical simulation parameters
dt = 0.01
# Update for all velocities under constant acceleration (gravity)
dv = V.vector(0,g*dt,0)
# Tolerance for deciding whether a collision happened
impact_distance = 0.5
# Initialize arguments
try:
v0 = float(sys.argv[1])
except:
v0 = v0_default
print 'Using default v0 =',v0,'m/s.'
# Build 3d world
# Define the line of sight
sight = V.vector(cos(theta),sin(theta),0)
# The floor is just a thin box
floor = V.box(pos=(D/2.,0,0), length=D, height=0.5, width=D, color=V.color.blue)
# Use a cone for our 'arrow'
arrow = V.cone(pos=(0,0,0), radius=0.9, axis=sight,color=V.color.red)
arrow.velocity = v0*sight
# The target is a sphere
target = V.sphere(pos=(D,H,0), radius=1, color=V.color.yellow)
target.velocity = V.vector(0,0,0)
# The 'dart gun' is just a cylinder.
gun = V.cylinder(pos=(0,0,0), axis=gun_len*sight, radius=1,
color = V.color.green)
# Run simulation
print 'Starting simulation...'
# Put a little delay to give all the OpenGL stuff time to initialize nicely.
time.sleep(1)
while (arrow.y >= 0 and target.y >=0) and \
V.mag(arrow.pos-target.pos) > impact_distance:
V.rate(75)
for obj in (arrow,target):
obj.pos += obj.velocity*dt
obj.velocity += dv
# Report to user.
if V.mag(arrow.pos-target.pos) <= impact_distance:
print 'Hit!'
else:
print 'Miss...'
#!/usr/bin/env python
"""Visual Python demo: shooting a falling object.
Note that this script can NOT be run inside ipython via the 'run' command.
You MUST run it from the command line as a standalone program. Start by doing
chmod +x shoot.py
(or whatever you called it), and then you can run it via
./shoot.py
"""
import time
import sys
# Visual is built on top of the 'old' Numeric, so do NOT use numpy here. We
# do a wholesale import for coding convenience, this is highly discouraged in
# larger codebases (but usually OK in very small demo scripts and interactive
# use).
import numpy as N
import math
from enthought.tvtk.tools import visual as V
def mag(v):
"Return the magnitude of a vector"
return math.sqrt((v*v).sum())
# Geometric parameters (all in MKS units)
theta = math.pi/4 # initial angle of gun
D = 20 # width ...
H = 20 # height of floor
g = -9.8 # gravity
gun_len = 2 # size of gun
arrow_len = 4 # and of arrow
v0_default = 15 # default for initial velocity if not given
# Numerical simulation parameters
dt = 0.01
# Update for all velocities under constant acceleration (gravity)
dv = V.vector(0,g*dt,0)
# Tolerance for deciding whether a collision happened
impact_distance = 0.5
# Initialize arguments
try:
v0 = float(sys.argv[1])
except:
v0 = v0_default
print 'Using default v0 =',v0,'m/s.'
# Build 3d world
# Define the line of sight
sight = V.vector(math.cos(theta),math.sin(theta),0)
# The floor is just a thin box
#floor = V.box(pos=(D/2.,0,0), length=D, height=0.5, width=D, color=V.color.blue)
floor = V.box(pos=(D/2.,0,0), length=D, height=0.5, width=D)
# Use a cone for our 'arrow'
#arrow = V.cone(pos=(0,0,0), radius=0.9, axis=sight,color=V.color.red)
arrow = V.cone(pos=(0,0,0), radius=0.9, axis=sight)
arrow.velocity = v0*sight
# The target is a sphere
#target = V.sphere(pos=(D,H,0), radius=1, color=V.color.yellow)
target = V.sphere(pos=(D,H,0), radius=1)
target.velocity = V.vector(0,0,0)
# The 'dart gun' is just a cylinder.
gun = V.cylinder(pos=(0,0,0), axis=gun_len*sight, radius=1,
# color = V.color.green)
)
# Run simulation
print 'Starting simulation...'
# Put a little delay to give all the OpenGL stuff time to initialize nicely.
#time.sleep(1)
while (arrow.y >= 0 and target.y >=0) and \
mag(arrow.pos-target.pos) > impact_distance:
#V.rate(75)
for obj in (arrow,target):
# obj.pos += obj.velocity*dt
obj.pos = obj.pos + obj.velocity*dt
#obj.velocity += dv
obj.velocity = obj.velocity + dv
# Report to user.
if mag(arrow.pos-target.pos) <= impact_distance:
print 'Hit!'
else:
print 'Miss...'
