SketchyPhysics Alpha

not registered yet

Can I use a spring like a piece of elastic?

What I would like is that the model starts with the elastic stretched, so that once the simulation begins it will try to shrink to zero length (or some other predefined minimum length) pulling any attached object with it.

Where-as the spring seems not to exert any force on attached objects until it is either streched or compressed from the start position.

Ampa

CPhillips

@ampa said:

Can I use a spring like a piece of elastic?

What I would like is that the model starts with the elastic stretched, so that once the simulation begins it will try to shrink to zero length (or some other predefined minimum length) pulling any attached object with it.

Where-as the spring seems not to exert any force on attached objects until it is either streched or compressed from the start position.

Ampa

It doesn't do that yet. Ill add it to my todo list.

Thanks Ampa.

not registered yet

This is a great plugin - congrats of the work so far.

Noticed one other bug: pressing Ctrl+Z (Undo) while the simulation is running causes seriously bad things to happen! Can Undo be disabled temporarily?

Some more playing…

I decided to create a chain, and tried in a number of ways…

Create rings (torus) and arrange them so that they interlock in 3d space. Why does this not work? I assigned Shape:convexhull, but this is obviously not correct.
Create rectangular 'chain links' where each 'link' is made of 4 cuboids. This should overcome the convex hull issue and be easier on the maths Indeed it works! But looks ugly!
A different sort of chain… Created a linear array of cubes and inserted a ball joint between each one. At this stage I have a vertical column of swinging cubes, but they all act independently. And I can't work out how to correctly group the joints with the cubes to create a single chain of linked cubes. What is the correct way to do this?

P: Ampa

CPhillips

@ampa said:

Noticed one other bug: pressing Ctrl+Z (Undo) while the simulation is running causes seriously bad things to happen! Can Undo be disabled temporarily?

Yeah, Ill mark it as a bug.

@ampa said:

Create rings (torus) and arrange them so that they interlock in 3d space. Why does this not work? I assigned Shape:convexhull, but this is obviously not correct.

A whole torus marked as convexhull will really resemble a solid wheel. If you want to create linked torus you need to break each segment of the torus apart into a convex hull and then group all the pieces. I did it once and it takes a while.

@ampa said:

A different sort of chain… Created a linear array of cubes and inserted a ball joint between each one. At this stage I have a vertical column of swinging cubes, but they all act independently. And I can't work out how to correctly group the joints with the cubes to create a single chain of linked cubes. What is the correct way to do this?

Group each of the ball joints with one of its two connected links and then use the JCT tool to connect the other link to the ball joint.

I should warn you that the ball joints aren't very stable when you connect them like this. The chain will fly wildly out of control if you try to move it too fast. This is a limitation of the underlying physics engine.

Chris

CPhillips

"Google Guy" has an example.

http://sketchup.google.com/3dwarehouse/details?mid=d49507b6e8b440efe476bbe10be2133b&prevstart=0

not registered yet

Chris, thanks for the pointers. It all makes sense now

Weee I have a dangle chain type thingy! I never knew how much I wanted one of these.

I look forward to further development, you've made a great tool / toy.

Ampa

bellwells

Hi Chris,

I had left a post over on the Google Groups about this, but thought I should mention it here as well. The strange images of guys playing crochet, etc are under the SketchPhysics directory at dhtml-suite-for-application>demos>demos-images. I would think they could be deleted??

Absolutely love this script.

diana

I am having a lot of fun with this script. Playing with the example files mostly; bowling, playing pool, trashing all the things that go round and up and down, tossing the doll about (got his head stuck through a wall once), etc. It's very entertaining! I realize it could be used as a tool as well, but I just want to play.

not registered yet

I was looking at giantmonster.tv today, and wondered whether one could use SketchyPhysics as an easy rigging tool for SU?

The code already exists to define joints between different objects, along with movement tollerences (max and min) so by turning off gravity a rag-doll becomes a posable-doll.

What do you think?

So I had a look at the SketchyPhysics options… turning off Gravity is easy to do; but I was unclear about what the other options did…

Density: presumably affects the mass of objects when they collide.
Framerate: defines the amount of discrete time that passes during each itteration?
Worldscale: er - no idea

I was trying to recreate space - ie no gravity or friction, but couldn't find a way. My objects always slow down, as if through air resistance. Is this possible?

Ampa

CPhillips

@ampa said:

I was looking at giantmonster.tv today, and wondered whether one could use SketchyPhysics as an easy rigging tool for SU?

The code already exists to define joints between different objects, along with movement tollerences (max and min) so by turning off gravity a rag-doll becomes a posable-doll.

What do you think?
Ampa

Possible in theory. But it would require some fairly big changes to the non-ruby code.

So I had a look at the SketchyPhysics options… turning off Gravity is easy to do; but I was unclear about what the other options did…

Density: presumably affects the mass of objects when they collide.

@ampa said:

Yes. It isnt much use now. It will be important in future versions.

@ampa said:

Framerate: defines the amount of discrete time that passes during each itteration?
Ampa

Yes. 1 is the minimum. Higher numbers will appear to go faster but wont be as smooth.

@ampa said:

Worldscale: er - no idea
Ampa

This is how big the world is. Use bigger numbers to increase the size of the world.

@ampa said:

I was trying to recreate space - ie no gravity or friction, but couldn't find a way. My objects always slow down, as if through air resistance. Is this possible?
Ampa

There inst any air friction that I know of. I am not sure why your objects would slow down in zero g.

Chris

namza

ping pong machine

pingpong4b.skp

CPhillips

@namza said:

ping pong machine

Very nice! It looks as cool as it works.

You should upload to 3d warehouse(use sketchyphysics tag).

Chris

namza

@cphillips said:

@namza said:

ping pong machine

Very nice! It looks as cool as it works.

You should upload to 3d warehouse(use sketchyphysics tag).

Chris

ok its done

namza

funny mouvement mooving cylinder or rotate box

Hyperboiloid_mouvement.skp

namza

the same with balls

ball roundabout.skp

not registered yet

Hey Chris, where can I download SketchySolids Toolbar and how do I drag objects? I ot a LOT of trouble with that.

Invader ZIM

CPhillips

@unknownuser said:

Hey Chris, where can I download SketchySolids Toolbar and how do I drag objects? I ot a LOT of trouble with that.

SketchySolids is part of SketchyPhysics.

There are instructions and a tutorial on dragging on the homepage:

http://code.google.com/p/sketchyphysics/

not registered yet

@cphillips said:

@unknownuser said:

Hey Chris, where can I download SketchySolids Toolbar and how do I drag objects? I ot a LOT of trouble with that.

SketchySolids is part of SketchyPhysics.

There are instructions and a tutorial on dragging on the homepage:

http://code.google.com/p/sketchyphysics/

I got this really bad error here. Can you help me?

Invader Zim

error i didn't like.JPG

CPhillips

That picture is almost unreadable. But I think the problem is you don't have the files in the right place. Follow the instructions here:
http://code.google.com/p/sketchyphysics/wiki/LatestVersion

Masta Squidge

If the "staticmesh" creates an object that followed the actual geometry of whatever it is, wouldnt it make sense simply to make all objects mesh objects though not static?

wouldnt that do away with all the work of having to change each item, and fix the problem with making a closed torus into nothing more than a cylinder from the viewpoint of the program?

Im sure there is a reason for it, but wouldnt it be easier to work with if all object were made as "mesh" objects that follow the geometry of the item, then you would only need to assign static, frozen, or ignore values to each item.

Also, as was posted before, pressing "Ctrl-Z" while in a simulation causes objects to "explode" and move around the scene. Its not easy to fix.

AND, sometimes when i make a floor when the "default" scene is acticve, then delete the default floor to play with the four objects, after they go out of the boundary of the default scene floor, they drop through the newly placed floor (yes its a solid object) while items i have made have no trouble with it at all.

All in all, very nice work.

Oh, and by the way:

Hi guys!! Im new here (obviously) and am currently in the process of being miserable with this plugin, and the two videos i have seen on it dont teach me anything more than how to place a hinge and stack up objects during a simulation.

If anyone would like to perhaps give me a hand with this, i would be grateful, as any "tutorials" that i find dont really teach me anything.