SketchyPhysics 3.5.6 (26 January 2015)

Anton_S

I don't remember if previous versions of SP also showed this behaviour: Positive values for the blue axis (e.g. a piston slider) move things down, in negative direction, whereas positiv values for the green or red axis move things in positiv direction. This irritates me. A bug?

Can you show an example, I can't reproduce this.

@platinius said:

The other issue I want to address are units. I always use metric units but SP converts them in imperial. For instance, when I position a piston and give it a length of 100 mm (by typing 100 a hitting enter while drawing) the UI max box shows a value of 3.93... which are inches. When I type 100 into the max field, the piston moves 100 inches, not millimeter. I would appreciate it a lot if SP used the units as set in the model settings window. Actually all boxes in the UI should be labeled with the unit expected (the unit set in the model settings). For example, what's the unit of density? What's the angle unit? Radian or degree? And Strength? This would make things a lot easier.

I can't change it because it could break compatibility with prior models, but I can make it to evaluate everything in the control box. For example, if you write 100mm it will turn it to 3.93.

Hinge min max values are in degrees. Density and strength is undetermined, it very complicated as SP bases everything on world scale. The default world scale is 9. This means all objects are assumed 9 times bigger or smaller (i cant recall), which as of results yields different volume, and mass. The volume is assumed in inches, thus the mass should be in volume_in_inches*density, where density depends on user input. Stuff are relative in SP.

ashscott

This is such awesome news! Can't wait to dig into it!

cotty

@anton_s said:

I will send an error message to them for this version as well. Yet, I can't fix it, as there are too much errors. Use version 3.6.28.3 with the fix I provided in the first post. Otherwise, you'll have to wait till they fix it.

A new version is out and the changelog says: "Fixing up SketchPhysics export" (not tested).

platinius

@unknownuser said:

Can you show an example, I can't reproduce this.

I'm sorry about that, it seems I didn't try enough. There is no difference between the axes. It irritated me that the moving direction of a piston or slider is opposite to the direction I choose with the mouse when positioning. For example, if I put a slider joint on the corner of a box and drag the mouse to the positive green direction it will move only to the negative direction.

@unknownuser said:

I can't change it because it could break compatibility with prior models, but I can make it to evaluate everything in the control box. For example, if you write 100mm it will turn it to 3.93.

Maybe this would help a little bit. To put the units besides the input boxes would be great and help people also. Maybe you know that a Mars orbiter crashed in 1999 due to falsely used units. I assume no one uses SP to constructed actually flying space ships, still it feels good to know what units one uses.

I found this thread which gives some information about units in SP:
http://sketchucation.com/forums/viewtopic.php?f=61%26amp;t=53209

A world scale factor of 1.0 and gravity of 9.81 (m/s²) seems to be suitable if using metric units.

Maybe this thread is of interest for you also. Looks like SP's author asked this question:
http://newtondynamics.com/forum/viewtopic.php?f=9%26amp;t=4684

Anton_S

To make the mouse control desired, simply multiply the whole controller by a negative sign.

I will add a list-box from which you could choose the type of limits angle/length.

Anton_S

@cotty said:

A new version is out and the changelog says: "Fixing up SketchPhysics export" (not tested).

Cheers!

It exports without problems, although the error comes when try to run the exported animation in Indigo render 3.6.28. Maybe I should download Indigo 3.8.x which is not available yet?

cotty

@anton_s said:

Maybe I should download Indigo 3.8.x which is not available yet?

You'll find the newest beta in the forum: http://www.indigorenderer.com/forum/viewtopic.php?f=1%26amp;t=13252

Trobius

Hi there! I've been an on and off user of sketchyphysics since 2.0.

Would it be possible to create a way to get an emitted object's lifetime? I know about the setLifetime function, but is there a similar "getLifetime?"

Anton_S

Hello, William!

Yes, SP doesn't have these methods. The API is quite incomplete.
I just added getLifetime, getLifeStart, and getLifeEnd.

Is there any other getter or setter functions you think shall be added before I post an update? Sorry, I can't think of any myself.

ashscott

You're a champ Anton, your efforts are very much appreciated.

Wish I had time to get back to some of the SP work I was doing earlier.

If anyone wants SP inspiration, check this model out: https://3dwarehouse.sketchup.com/model.html?id=5b618d4ba6c22ca85fd35d52fb19ea9b

In fact, all of Phonic's work is pretty amazing: https://3dwarehouse.sketchup.com/user.html?id=0127263341868366760323686

Anton_S

Thanks, Ash.

Lately, I haven't created any SP either. I suppose, that is because I kinda lost passion in it.

Phoenix is a good SP modeler. He's sharing some great stuff!

Mr.K made some amazing things too. For instance, take a look at the Blue vs Red. You control the bot to get across the puzzle. It may appear mind boggling at first, but you'll get it mastered after some experience.

ashscott

Have you had any interaction with Phonic? I couldn't get a response when I tried some years ago - I wondered if he was only mandarin speaking.

Anton_S

@ashscott said:

Have you had any interaction with Phonic? I couldn't get a response when I tried some years ago - I wondered if he was only mandarin speaking.

Nope, I haven't. I doubt that Phoenix even reads the comments. Usually people respond to their comments by updating the model description with responses, but I never seen him do that.

ashscott

One thing with Sketchyphysics I did wonder about - and I have no idea how to execute it - would be a "Cut" function. I have modeled saw milling machinery with SP in the past but always had to do some variation of a breakable joint to simulate cutting - due to the physical reactions in breaking a joint, you can understand that it wasn't pretty.

Any idea how to cut an object so that it becomes two?

Anton_S

Piece of cake!

Copy this piece of code into the scripted field of the body that you want to be cut:


onTouch {
  split(self, 2)
}

What happens is that it splits when it is touched by another body. Increasing the value will create more cuts.

Of course, the code may be changed to have the body be split in another occasion, for instance when it touches a particular body, or at specified frame... If you provide some instructions I could easily write you a code.

Here is a little example:cut_body_example.skp

ashscott

Very cool!

I think I've seen some reference to this before.

How would I control the cut so it occurs in a specific place?

For example, on a piece of wood - to only be cut where the saw touches it?

Ash

Anton_S

SP doesn't have this method, but I created my own.
https://3dwarehouse.sketchup.com/model.html?id=ua22b41f2-9654-4d70-898b-46d96e687272

ashscott

Anton,

I am stunned

I have tried so long to get a working function like what you've shown and have failed miserably - this is totally amazing. I hope you don't mind me pillaging your code for ideas?

Frenchy:
@unknownuser said:

And also the white cross texture box "transparent" who is drawn

For some reason "Hidden Geometry" is getting turned on when I run an simulation the first time. Go >View>Hidden Geometry to turn it off.

pilou

Cool function!
But seems there is a glitch!

When I use these 2 menus!
After the Record Animation, replay etc...
Animation is stopped at the moment of the box must be "exploded" on the inclined plane!
Can you verify this ?

And also the white cross texture box "transparent" who is drawn!
This is the image of the result wished!

cut_body_example_glitch.skp

pilou

Thx