@hpnisse said:

Hey, robint!

Your chain works perfect when you set the collision state correct in every single object
[attachment=0:au7zhech]<!-- ia0 -->Re. my chain 1.skp<!-- ia0 -->[/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

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

@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

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

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

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?

here my 2c worth for sp 3.2

if you want to make a reversible motor joint, use the hinge (as per sp2) and set the controller blue box to

quote slider ( 'anyname' )

you can see the same construction using the motor joint

wish I didnt have to waste hours getting to this point.

Also

to make magnetic solids work you need to set the ui box status to magnetic
and the magnetic force to a large value eg +- 1000

not obvious is it?

I wonder whether its worth contributing to a wikimanual at5 this stage if thereis going to be an sp4 completely recoded?

Robin

This site seems to be moribund, not a lot happening?

Anyway Ive solved the UI problem

so all working ok now

Hi guys

how or where do I post a skp model for discussion

also i cant post a link here?

robin

Hi all

great stuff pls keep it up. I will try to add my 2 cents as i progress
I cant post any links or skp models to demo my points, this is very limiting

Hi

i think ive solved the mystery re-installing su8 and sp3.1, the ui window now works BUT i cant make a revesrsible motor out of a hinge

I discovered that I could also instal sp2.o1b and this would allow a hinged reversible motor, why did this get left out of sp3?

Cant get the spring to do anything, and what does the corkscrew do other than reveolve in an uncontrolled way?

Lots of bugs to sort out in this plug in

robin

Hi guys

Im sure we all agree the math is the easy bit and I programmed it into Xcel to give the 3D coords - fine, but you have to input them to su to 10 decimal places to get fully coherent filled planes and accuracy - very tedious.

In case I didnt explain myself properly, just try constructing a 2D
d triangle with 3 unequal side say 1, 2 , 3

you wont manage it in SU by construction but you can calculate the point of intersection but to 10+ decimals

then go to the 3D case where you construct a tetrahedron all with unequal sides

I will look at the other stuff posted in the next couple days

cheers new year thingy

help UI window not working

Postby robint on Mon Jan 03, 2011 8:59 am
ive got su8 latest and sp 3.2 installed

when I try to inspect joints i get the usual info for a hinge (say). when I try to input say accel or a controller name , it accepts them but doesnt do anything - no slider in the run panel

Ive tried the other tip of clicking on the UI button to exit the UI window to no avail

I saw a tuorial where it said that you can turn a hinge into a reversible motor by putting accel = 1 and giving the controller a name - which is then supposed to bring up a slider in the run panel - i just get a blank.

then i go back and look again and just get blank boxes. only restarting su8 will clear the prob but it comes back if I try to change a parameter

cheers Robin

ps I havent got so excited since I first used SU4 - this could be a wonderful educational tool if physical values could be added to demonstrate newtons laws for example

I made a double pendulum the other day, but as already said, there's lots of real world physical attributes to be addressed (eg mass, density, friction, elasticity etc) but its early days

Hi TT

sorry pardon, it is indeed related to sketchyphysics rc2 and I thought I had posted in that forum, pls relocate my query

thanx

ive got su8 latest and sp rc2 installed

when I try to inspect joints i get the usual info for a hinge (say). when I try to input say accel or a controller name , it accpts them but doesnt do anything - no slider in the run panel

then i go back and look again and just get blank boxes. only restarting su8 will clear the prob but it comes back if I try to change a parameter

Hi all

some years ago SU5 days, I came across a problem requiring the intersection on a circle with a line of fixed length (not a tangent). This proved impossible in SU because as we know a circle is a collection of segments. I was able to do the simple math (on Xcel) and input the 10 digit decimal of the coordinates on the 2D surface. Clearly a very cumbersom procedure but it worked. At the time Ruby came out but I didnt have the time to devote to learning it sufficiently. I guess now there are thousands of you smart guys out there who could whistle up a little plug in to do this seemingly mundane task.

I did go on further to do the math for the 3D space which produced all three coordinates for the exact point. As we all know you have to be exact or your plane wont fill and its downhill all the way after that.

I could replicate the math in pseudo code - simple enough to understand if you knew excel notation and only comes out at about 10 lines of simple algebra

Would any kind soul be interested in collaborating on this as the use of this tool is not at all trivial.

Cheers RobinT

Cheers robin