Illustrative ex for viz #11

tarzzz · 2013-06-23T08:02:03Z

Added code according to PEP8 conventions

Added a 3 link pendulum problem, with links as RigidBodies

Changed inertia value

…ples into 3-link-pendulum

pydy_viz

chrisdembia · 2013-06-23T17:01:05Z

illustrative_example_for_viz/illustrative_example.py

+    point = link.get_masscenter()
+    forces.append((point, -mass * g * I.y) ) 
+
+kinetic_differentials = []


This is a picky comment, but differentials are different from differential equations. Also are these kinematic or kinetic? The word kinetic is sometimes used to mean "dynamic" (that is, coming from F=ma).

these are kinematic equations.

On 6/23/13, Christopher Dembia [email protected] wrote:

+#Applying forces on all particles , and adding all forces in a list..
+forces = []
+for particle in particles:
+

mass = particle.get_mass()

point = particle.get_point()

forces.append((point, -mass * g * I.y) )

+#Applying forces on rigidbodies ..
+for link in links:

mass = link.get_mass()

point = link.get_masscenter()

forces.append((point, -mass * g * I.y) )

+kinetic_differentials = []

This is a picky comment, but differentials are different from differential
equations. Also are these kinematic or kinetic? The word kinetic is
sometimes used to mean "dynamic" (that is, coming from F=ma).

Reply to this email directly or view it on GitHub:
https://github.com/PythonDynamics/pydy_examples/pull/11/files#r4833547

yes, the correct term is "kinematic differential equations"

chrisdembia · 2013-06-23T18:19:44Z

Hey Tarun, cool stuff. I made some notes.

moorepants · 2013-06-24T16:49:09Z

How about changing this example so that it imports the results of your three pendulum example and this would only have the code for the simulation and visualization. Right now you have the same code in both files and have to maintain them both.

moorepants · 2013-06-24T16:53:36Z

illustrative_example_for_viz/illustrative_example.py

+                      'l3':1.0, 'm1':2, 'm2':2, 'm3':2, \
+                      'M1':5, 'M1':5, 'M1':5]
+
+json = frame1.generate_json(initial_conditions, q)


Shouldn't this take the results from odeint + some output equations numerical results and then generate a json file? It doesn't seem like the correct info will be available here.

this is just a visualization at (well in this case) t=0.
so we know initial-conditions and shapes/objects info at t=0. we can
visualize it.

for animation we would certainly require json generated from this
output + numerical-vals from odeint.
although if we want to implement the visualization at any specific
time other than initial(t=0), then it would certainly require
numerical-vals.
but on the other hand, in future we will allow user to fast fwd
animations to specific time, so it might be deprecated.

On 6/24/13, Jason Moore [email protected] wrote:

+numerical_vals = odeint(right_hand_side, init_conditions, t)
+
+#Now for each t, we have numerical vals of coordinates ..
+#Now we set up a visualization frame,
+
+frame1 = VisualizationFrame('frame1',I , O)
+
+frame1.add_rigidbodies(links)
+
+frame1.add_particles(particles)
+
+param_vals_for_viz = {'g':9.8, 'l1':1.0, 'l2':1.0, \

'l3':1.0, 'm1':2, 'm2':2, 'm3':2, \

'M1':5, 'M1':5, 'M1':5]

+json = frame1.generate_json(initial_conditions, q)

Shouldn't this take the results from odeint + some output equations
numerical results and then generate a json file? It doesn't seem like the
correct info will be available here.

Reply to this email directly or view it on GitHub:
https://github.com/PythonDynamics/pydy_examples/pull/11/files#r4846400

I don't think there is any reason to make different things for visualizations at t=t1 versus t=t0 versus t=[1, 2, 3, 4, 5]. You're methods should accept any numerical values of t and output equations (functions of q) to generate the visualization. If you supply values at one instant of time then you get a static visualization, but if you supply lists/arrays then you should be able to play the animation through time. These are not distinct cases (static viz at one config and animations). A static viz is just one frame of the animation.

chrisdembia · 2013-07-09T20:42:15Z

illustrative_example_for_viz/essential.py

+#also it doesnot check for TypeErrors etc.
+
+class MeshShape(object):
+    def __init__(self,name,point_list,color='grey',origin=[0,0,0]):


spaces after commas

chrisdembia · 2013-07-09T20:57:42Z

I know that the essential.py is posted so that the example can work, but I would encourage you to use a more descriptive name in the future. The name essential doesn't really tell me what's in that file.

chrisdembia · 2013-07-09T20:58:38Z

How come there are 2 three_link_pendulum.py files now?

chrisdembia · 2013-07-09T23:33:47Z

illustrative_example_for_viz/illustrative_example.py

+frame3 = VisualizationFrame('frame3', link3, shape=shape3)
+
+scene = Scene('scene1',I,O)
+scene.vframes = [frame1,frame2,frame3]


I think it would be better if there was not a setter like this; see other comment.

chrisdembia · 2013-07-09T23:51:00Z

This has to do with illustrative_example.py:

I know I've said it before but I find it unnecessary for the user to make the visualization frames on their own. They could easily just forget to add one of the bodies in their multibody system. I imagine something like this:

scene = Scene('scene1', KanesMethod) # assuming Kane's Method knows about inertial frame.
# This will initialize a VisualizationFrame for each rigid body, with names <body_name>
print scene.vframe['link1']
scene.vframe['link1'].shape = shape1
scene.vframe['link2'].shape = shape2
scene.vframe['link3'].shape = shape3

I wish the pydy interface were a little different, so that this would ideally be:

sys = System('three_link_pendulum')
sys.add_rigid_body(RigidBody('link1', ...)
sys.add_rigid_body(RigidBody('link2', ...)
sys.add_rigid_body(RigidBody('link3', ...)
km = KanesMethod(sys)
# ...
scene = Scene('scene1', sys)
# as above

If we need to, we could resort to:

scene = Scene('scene1', body_list)
# as above

just as we pass a body list to KanesMethod. I think that this is better than doing the wiring between VFrames and RigidBody's ourselves. I'm happy to discuss this though.

moorepants · 2013-07-22T19:12:58Z

Tarun,

Please git rm js/output.json because there are always conflicts when trying to switch branches and merging etc. It is a real nuisance. My modifications to the code allowed for much faster generation so it shouldn't be necessary to hang on to it. We can speed things up faster too once I figure out a few issues.

moorepants · 2013-07-22T20:09:17Z

illustrative_example_for_viz/essential.py

+        self._transform = Identity(4).as_mutable()
+
+    def transform(self, reference_frame, point):
+        # TODO : make sure this actually works correctly


I wrote this here because I was having some trouble with evaluating the matrix with lambdify and array arguments. There may be a better way to construct this matrix, but it is probably fine for now.

moorepants · 2013-07-25T16:36:11Z

Remaining items before merge:

Fixed links in animation to have cylinders end at the joints.
Add spheres for the particles.
Add a better figure.

…ples into illustrative-ex-for-viz

… for the particles.

…y_examples into illustrative-ex-for-viz Conflicts: illustrative_example_for_viz/illustrative_example.py illustrative_example_for_viz/simulate.py

tarzzz · 2013-09-22T18:50:43Z

@moorepants It can be merged now ..

moorepants · 2013-09-22T21:32:11Z

illustrative_example_for_viz/README.rst

+
+    $ git clone https://github.com/PythonDynamics/pydy-viz
+
+2) Add the directory to the PYTHONPATH::


It would be better to instruct them to actually install it here:

cd pydy-viz
python setup.py install # use sudo if you want system wide install

You can do the python path trick addition as an option.

It'd be best if you showed how to run each file in this directory indenpendently. You have the derivation file, the simulation, and the visualization.

Ideally the user could type three commands to run things individually:

python derive.py python simulate.py python visualize.py

The results of the previous command could be pickled to file so that the subsequent file could load the data. If the data isn't available on disk, then it can run

try: open('simulate-data.p') except IOError: import simulate # runs simulate.py if data doesn't exits # do the simulation ... # pickle the results pickle.dump(simulation_results)

This adds the example problem Tarun developed and used when designing the visualization package. I've updated it to run with the current version of PyDy. The original pull request can be found here: pydy/pydy_examples#11

tarzzz added 7 commits June 19, 2013 01:49

Added a 3 link pendulum problem, with massless links. and

06398c4

Added a 3 link pendulum problem, with links as RigidBodies

Added README

11a0059

Changed inertia value

Update three_link_pendulum.py

d5f2d44

Modified script for two dimensional joints

a61e602

Merge branch '3-link-pendulum' of https://github.com/tarzzz/pydy_exam…

e69d5cf

…ples into 3-link-pendulum

Added an illustrative example to demonstrate the workflow of

89db91f

pydy_viz

Updated to include code according to PEP8 style guide

b10d0e5

chrisdembia reviewed Jun 23, 2013
View reviewed changes

moorepants reviewed Jun 24, 2013
View reviewed changes

[WIP] Added some base classes for the illustrative example

b1a923c

chrisdembia reviewed Jul 9, 2013
View reviewed changes

Working example now. Modified both python and Javascript code.

cb5ba46

moorepants reviewed Jul 22, 2013
View reviewed changes

moorepants and others added 12 commits August 6, 2013 17:47

Changed time.

8314218

Modified according to new code for pydy_viz

d11bd84

WIP

5ef35c4

Removed white spaces

733f2ca

Modified illustrative_example source

85b715e

Merge branch 'illustrative-ex-for-viz' of github.com:tarzzz/pydy_exam…

9fcf6bb

…ples into illustrative-ex-for-viz

Attempt to fix up the animation with correct link lengths and spheres…

4ea2488

… for the particles.

Removed comma.

0fec414

Removed extraneous line.

18ad2b2

Modified README

cde87c8

Modified README

53bddd4

Merge branch 'clean_conical' of https://github.com/PythonDynamics/pyd…

896a29f

…y_examples into illustrative-ex-for-viz Conflicts: illustrative_example_for_viz/illustrative_example.py illustrative_example_for_viz/simulate.py

moorepants reviewed Sep 22, 2013
View reviewed changes

moorepants mentioned this pull request Sep 22, 2013

[WIP] 3 link pendulum #10

Open

moorepants mentioned this pull request Jun 29, 2014

Adds a three link conical pendulum example. pydy/pydy#72

Merged

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Illustrative ex for viz #11

Illustrative ex for viz #11

tarzzz commented Jun 23, 2013

chrisdembia Jun 23, 2013

tarzzz Jun 24, 2013

moorepants Jun 24, 2013

chrisdembia commented Jun 23, 2013

moorepants commented Jun 24, 2013

moorepants Jun 24, 2013

tarzzz Jun 24, 2013

moorepants Jun 24, 2013

chrisdembia Jul 9, 2013

chrisdembia commented Jul 9, 2013

chrisdembia commented Jul 9, 2013

chrisdembia Jul 9, 2013

chrisdembia commented Jul 9, 2013

moorepants commented Jul 22, 2013

moorepants Jul 22, 2013

moorepants commented Jul 25, 2013

tarzzz commented Sep 22, 2013

moorepants Sep 22, 2013

moorepants Sep 22, 2013

moorepants Sep 22, 2013


		$ git clone https://github.com/PythonDynamics/pydy-viz

		2) Add the directory to the PYTHONPATH::

Illustrative ex for viz #11

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Illustrative ex for viz #11

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tarzzz commented Jun 23, 2013

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chrisdembia commented Jun 23, 2013

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chrisdembia commented Jul 9, 2013

chrisdembia commented Jul 9, 2013

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