SketchyPhysics3.2 (Dec 2)

robint

High CP

I have used Poser 5 in the past and learnt about inverse kinematics and joints

I think there is a fundamental limitation that prevents you making a chain of joints because the last child joint has to join the first parent so the parent must then become a child. This would be inherently unstable (like positive feedback) which is why the joint flies apart in pieces

Can anyone confirm my guesswork or poiont me somewhere that a working chain has been made (ie will revolve around a sprocket

cheers robin

hpnisse

Hey, robint!

Your chain works perfect when you set the collision state correct in every single object
Re. my chain 1.skp

Oxer

Hi,
I have installed SketchyPhisics 3.2 on Mac with OSX 10.6.6 and SU8 and the plugin don't woks, SU read the plugin, appear the toolbars, you can create the shapes but when you press the play appears a window with this message:
Error initializing the Simulation: : uninitialized constant MSketchyPhysics3::SP3xSimulationContext::SPSounds /Users/Oxer/Library/Application Support/Google SketchUp 8/SketchUp/Plugins/SketchyPhysics3/ControllerCommands.rb:777:in `initialize'
And in the ruby console this:
%(#FF0000)[String doesn't compile: uninitialized constant MSketchyPhysics3::SP3xSimulationContext::SPSounds#<NameError: uninitialized constant MSketchyPhysics3::SP3xSimulationContext::SPSounds>
/Users/Oxer/Library/Application Support/Google SketchUp 8/SketchUp/Plugins/SketchyPhysics3/ControllerCommands.rb:777:in `initialize'
/Users/Oxer/Library/Application Support/Google SketchUp 8/SketchUp/Plugins/SketchyPhysics3/sketchyphysicstool.rb:727:in `new'
/Users/Oxer/Library/Application Support/Google SketchUp 8/SketchUp/Plugins/SketchyPhysics3/sketchyphysicstool.rb:727:in `initialize'
/Users/Oxer/Library/Application Support/Google SketchUp 8/SketchUp/Plugins/SketchyPhysics3/sketchyphysicstool.rb:1623:in `new'
/Users/Oxer/Library/Application Support/Google SketchUp 8/SketchUp/Plugins/SketchyPhysics3/sketchyphysicstool.rb:1623:in `startphysics'
/Users/Oxer/Library/Application Support/Google SketchUp 8/SketchUp/Plugins/SketchyPhysics3/sketchyphysicstool.rb:1650:in `physicsTogglePlay'
/Users/Oxer/Library/Application Support/Google SketchUp 8/SketchUp/Plugins/SketchyPhysics3/sketchyphysicstool.rb:1738]
I have reinstalled SketchyPhysics3.1 and works.

robint

@hpnisse said:

Hey, robint!

Your chain works perfect when you set the collision state correct in every single object
[attachment=0:au7zhech]Re. my chain 1.skp[/attachment:au7zhech]

Hi H

Thanks for that tip, the model chain works for me now, but I dont understand how setting the object state to "show collision geometry" makes such a radicle difference?

obviously i dont understand this state? I looked on the tutor manual but that wasnt helpful
so i am puzzled

nice that one can actually make a set of revolving links

What we need now is a workable spring (with variable rate and damping). the legacy one only works in sp2.3 not in 3.2. perhaps its work in progress

can anyone tell me if joints have a built in friction?

A simple pendulum will slowly come to rest, so there must be some restraint or energy loss built in? is this variable?

in mechanical systems you need mass, stored energy (spring) and friction (damping) preferably using SI units so as to start physical modelling

BTW I was once involved with a brilliant guy who made an amazing music generating prog that allowed exploration of scales, rhythms etc. BUT he was a C++ script magician and his prog became a tangle compost heap of widgets with a poor and almost unusable manual. I tried to help sort out the mess but the guy simply couldnt organise his thoughts in a consistant and methodical manner so his brialliant concepts came to nought as prospective users lost enthusiasm and gave up.

If anyone is preparing to organise a proper manual for SP4 then I can offer my 2c worth

cheers

Robin

All good stuff as I had come to a brick wall till now

robint

hi all

Im posting some models that illustrate some points and queries

all comments gratefully received

Robin

[my cone n ball

rotates using a motor hinge (when will this become reversible?

Two balls used, small one falls to bottom so that larger one is off centre and crawls up the side and out otherwise just drops to bottom.

nice demo of centripetal force and a hollow solid](/uploads/imported_attachments/elvl_myconeandball1.skp)

[my lift ball

tried using lift capsule and got it working, then i moved the capsule and it all fell apart. but now i cannot recreate a lift capsul with a slider or a piston

strikes me that a slider is unnecessry as its the same as a piston but without accel and damping figures - so why bother.](/uploads/imported_attachments/E5tW_myliftball.skp)

[my rotating box

strange that the slider now makes a hinge behave like a servo
If you push tha slider to one end then the cube over turns and starts rotating in an erratic manner (like a ball running up and down a valley then gaining enough momentum to over top and run down the next valley.

before (maybe in a previous version of SP this feature would behave like a true reversible motor - now it doesnt? what happened

also if you get it going full speed one way then throw it into full speed other way, it crashes SU](/uploads/imported_attachments/wXwb_myrotatingbox1.skp)

[my spring box

cant get the spring to move at all. is it now not supported in sp3.2 ?](/uploads/imported_attachments/IRVt_myspringbox1.skp)

solodown

Toujours pas de nouvelles pour faire fonctionner ce plug-in sous Mac OS X 10.5.8 avec Google SketchUp ?

zunkian

Hi!

Is there a manual for SketchyPhysics for beginners?
If there is one, please upload.
Thank you.

Andy

derei

Indeed a user manual for users that did not used ketchyPhysics before would be nice. I noticed that some beginners tips are to be fond here http://sketchyphysics.wikia.com/wiki/SketchyPhysicsWiki , but I'm sure that version 3.2 have much-much more features than are detailed there.
Thanks.

4dHans

Could you do like explosions in a future version? That would be cool!

mickeyao

MBP with 10.5.8 Thanks!

sketchyKev

@robint said:

hi all

Im posting some models that illustrate some points and queries

all comments gratefully received

Robin

For the first one (rotating cone) you can make the motor reversible by changing the controller code to (slider('motor8055')-0.5)*2

Using that code the middle position of the slide control is off, full left turns one way and right turns the other way.

For the second one, to create a lift capsule do this:

Create a solid floor.
Place a wheel capsule with built in hinge on the floor.
Place a lift capsule with built in slider on the floor.
Using the JCT click on the hinge joint, then ctrl-click on the slider.
A menu pops up asking if you want to "Create a worm gear..". Click "OK".
Run the simulation and turn the hinge capsule clockwise and the other capsule should rise.

You can build a lift from scratch from components. Just make sure each joint is grouped with the moving objects and joint connected with something static before trying to make the worm gear connection.

For the record a slider is not a piston with the accel and drag values set to zero. A piston with those values will not move.

For the rotating box using a slide controller on a hinge, the program does not recognise a controller called "speed" so it has defaulted to servo behaviour. You can get the same behaviour from a servo by setting min=-180 and max=180. It is known that servos behave badly if you try to get them to complete full circles or more than one circle. There is no need to mess with the hinge controllers as servos and motors are provided.

For the box on a spring, the spring is orientated vertically and does not allow sideways movement or rotation. When you try to drag the box the drag action defaults to horizontal movement. To pull the box up or down inline with the spring you need to hold left-shift on your keyboard while dragging with the left mouse button. Try the spring orientated sideways and it should work fine. The springs are on the stiff side so it is worth playing with the accel and damp settings.

Hope that helps.

AlainBo

There are months now that sketchyphysics 3.2 installs 3.1 !!!

Don't understand this update !?

bouleaux

Hello,
congratulations for this marvellous job !
I'm using sketchup 8 on a Mac Book Pro running on Mac Os 10.5.8
and I would loooove to be able to use sketchyphysics with this computer
any chance ?
thx again

Oxer

@bouleaux said:

Hello,
congratulations for this marvellous job !
I'm using sketchup 8 on a Mac Book Pro running on Mac Os 10.5.8
and I would loooove to be able to use sketchyphysics with this computer
any chance ?
thx again

Hi, bouleaux
I'm a mac user too, the last version 3.2 doesn't work on Mac but the 3.1 version works fine on OSX Leopard with SU 8.
I hope this help you.

bouleaux

Hello Oxer, many thanks
I tried to find the 3.1 version, but it doesn't seem to be available for download anymore (on this page : http://code.google.com/p/sketchyphysics/downloads/list)
Do you know of another place to find it ?
Thank again for your answer

Oxer

@bouleaux said:

Hello Oxer, many thanks
I tried to find the 3.1 version, but it doesn't seem to be available for download anymore (on this page : http://code.google.com/p/sketchyphysics/downloads/list)
Do you know of another place to find it ?
Thank again for your answer

If you want i can send it you by PM

AlainBo

Hi,

I tried to add kaybord control on my physified lynx crane but I cannot get it working properly.
It actually works with sliders so, the joint position is given by the slider position so the crane's arm, for example stays in the position set by the slider.

With keybord control it's different and even if I can move the arm with a key, it cannot stay in position when I release the key.

original joints where servo. I tried to use a motor instead but the result is almost the same.

Any idea?

lynx_100ton_mobile_crane SP_KB.skp

ashscott

Here is the answer to your question from this thread: http://forums.sketchucation.com/viewtopic.php?f=61&t=44399

There is a much better answer than using a motor to place a joint where you want it - you need to use a servo and a little ruby script

Step1: place your servo within the group you want to move and attach it to a base group
Step2: select the servo and open the sketchyphysics UI
Step3: within the UI apply the following settings

min:0
max:1
accel:4000
damp:1000
controller:@servo1 (you can actually call it anything starting with @

Step4: Select the base of your model and open the sketchyphysics UI
Step5: place the following rubyscript in there:

    if frame<1.00
    @servo1=0.00
    end
    # this allows servo to incrementally increase based on joystick input (righty) you can change it to any of the joystick axes
    @servo1+=(0.5-righty)
    # this sets range of movement for the servo as it is not set in the servo's UI
    if @servo1>45;@servo1=45;end
    if @servo1<-45;@servo1=-45;end

It took me a long time to work this out (reverse engineering another model) so I am more than happy to help anyone out with it if these instructions are too hard to follow.

I believe this is a very powerful function in sketchyphysics and I have only seen it in one model in the 3DWH

AlainBo

Hi Ashscott,
Thanks for your answer.

I tried your script and one I wrote and in any case I get the following error when I start the simulation:

Error starting the simulation: Error in Script:

...

undefined method'<' for nil:NilClass
C:/Program......../ControllerCommands.rb:1314:in 'initEvents'

It something is not correctly initialized. Is there something to import at the beginning of the script or something like that?

Any idea?

Is there any wiki on the basics of keyboard control? The only one I know is http://sketchyphysics.wikia.com/wiki/Ruby.

ashscott

You need to make sure that the name of your servo in the controller box (select the servo and press the 'UI' button) is the same name used in the script - in the example I have used the name '@servo1'

It looks like it is spazzing out because you haven't got a name right somewhere......