SketchyPhysics3.2 (Dec 2)

robint

Hi JB

good point

afik though there is a density coeff, I dont know how well it correlates to the mass of an object?
the apparent mass i governed by the size of the collision shape as set in the rt click physics setting

havent figured this tiresome details out yet

I have a number of cu4rious physical models i would like to post for discussion (eg double pendulums etc) but havent yet found a way to post these little experiments.

It seems daft that one cant attach these on this forum - severly limiting

Any ideas?

CPhillips

Yes magnets are effected by the size of an object.

You can attach files to posts. Look at the bottom of the form and there is an "Upload Attachment" tab.

robint

hi all

sorry pardon didnt see the tab for uploading

I was trying to make a chain rotating around 2 sprockets. The chain seems to want to fly apart, its all chaotic? even though its all supposed to be stationary, any ideas

btw i have su8 and sp3.2 dec2010

its all good fun but i wish i had more control over the way things work, bit hit and miss at the moment

btw although bugsplat is a good tool, i dont connect my main machine directly to the net for obvious security reasons, so cannot utilise bs directly. It would be much more convenient if bs made a composite text file stored conveniently which i could gather up and post here to help with su crashes. Its a bit cumbersome at the moment

cheers robin

a chain loop goes wrong

TIG

CPhillips
Please see here for an 'issue' with group.definition http://forums.sketchucation.com/viewtopic.php?p=300105#p300105

robint

hi CP

thanx for the tip, will see if i can make it so.

any pointers on where to start on Ruby so i can at least know something of what im doing?

cheers

Robint

robint

@tig said:

CPhillips
Please see here for an 'issue' with group.definition http://forums.sketchucation.com/viewtopic.php?p=300105#p300105

Hi
I tried the code but it seemed to make things worse

Code: Select all
class Sketchup::Group
if not Sketchup::Group.method_defined?(:definition)
def definition() # make it so you can use group.definition
return(self.entities.parent)
end
end#if
end

something about a chain sp doesnt like

Im stuck, my chain flies apart

robin

attemtped chain

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.