Animated 3D models of Steam Engines

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microelly2
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Re: Animated 3D models of Steam Engines

Postby microelly2 » Mon Dec 22, 2014 12:42 pm

romartin wrote: but am not sure what you mean by a Plugger.
I have started an animation workbench some month ago.
the documentation is on my website http://freecadbuch.de/doku.php?id=Animation%20Wokbench
there is a list of clips for the features.

the plugger connects a part to a vertex inside of an animated sketch.
there is a demo clip that shows the plugger functionality on a star motor http://youtu.be/v6oFOr8EW4U

I'm doing here the same like you. A sketch animates the rotation and the movements of the pistons.
the real parts are connected to the vertexes inside the sketch by pluggers.
I'm interested in a framework that allows me to animate without extra python coding necessary for the enduser.
So meanwhile a list of objects are created.
I'm now on the way to implement more complex patterns - a gearing system, a kardan wheel and currently the geneva wheel.
jmg works on a sheet metal tool and a unfold process. he has published this weekend his assembly animation workbench. it works similiar. With this tool you can interactive create an animation without extra code. See this
viewtopic.php?f=24&t=9028&p=73456#p73456




http://freecadbuch.de/doku.php?id=blog: ... verfeinert
romartin
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Re: Animated 3D models of Steam Engines

Postby romartin » Mon Dec 22, 2014 5:27 pm

Thank you microelly2 for this information. I have followed the links and think I have understood the objectives of the Animation WB you are building. I will follow your progress with interest.

During the development of my animated steam engine models I became aware that the technique for using a fully constrained Sketch to calculate the placements for the moving parts of a 3D model could probably be generalised. Now I see you have been working on it for some months. Here are a few ideas and issues which come into my mind: forgive me if I am missing the point:
  • The animation of a certain model may be more readily expressed by more than one Sketch. In the case of my Engines for example, the Sketch I defined models the movement of the Reversing Mechanism but not the movement of the Piston Assembly and the ConRod Assembly which my macro animated by using explicit trigonometry.
  • Conversely, the same sketch may be used to model the movements of a number of simlar or identical sub-assemblies in the 3D model. In the case of my dual cylinder Engines for example there is a seperate Reversing Mechanism associated with each cylinder; the axes of the two dual eccentrics have a 90 phase difference and so for each step of the animation, the Sketch gets solved twice, once for each of the two reversing mechanisms.
  • The moving parts of a model may have more than one degree of freedom. In the case of my engines, the model has two degrees of freedom which we can think of as the angular position of the crank shaft and the angular position of the reversing lever. I can imagine models with many degrees of freedom, for example models of architectural scenes with people and vechicles.
Ciao, Ian
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microelly2
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Re: Animated 3D models of Steam Engines

Postby microelly2 » Tue Dec 23, 2014 11:15 am

romartin wrote: [*]The animation of a certain model may be more readily expressed by more than one Sketch. In the case of my Engines for example, the Sketch I defined models the movement of the Reversing Mechanism but not the movement of the Piston Assembly and the ConRod Assembly which my macro animated by using explicit trigonometry.
Yes, sketches can work in parallel (a two foot walking robot), but cascaded sketches are possible too (landing a shuttle on an asteroid or vary with the head/center of gravity while walking)
[*]Conversely, the same sketch may be used to model the movements of a number of simlar or identical sub-assemblies in the 3D model. In the case of my dual cylinder Engines for example there is a seperate Reversing Mechanism associated with each cylinder; the axes of the two dual eccentrics have a 90 phase difference and so for each step of the animation, the Sketch gets solved twice, once for each of the two reversing mechanisms.
there is the possibility to combine the results of one sketch with a transformation matrix which can do affine mappings
[*]The moving parts of a model may have more than one degree of freedom. In the case of my engines, the model has two degrees of freedom which we can think of as the angular position of the crank shaft and the angular position of the reversing lever. I can imagine models with many degrees of freedom, for example models of architectural scenes with people and vechicles.
I bind the degrees of freedom to constraints which are controlled from outside by my adjustor objects. So the sketch is always completly determined and the solver has only to find the right solution.
I still have no idea what to do if the system is not solvable. Currently I hate ambiguous systems. An open problem is how to handle dead points: If you start the animation from the piston there are the two poles where the movement in reality follows the inertia but the sketcher solver can fall back too. so there is the need to bring physics (forces) into the system. but this is still far away. :?

see
http://bulletphysics.org/wordpress/
and
http://www.warp1337.com/content/blender ... -modelling
drei
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Re: Animated 3D models of Steam Engines

Postby drei » Tue Dec 23, 2014 7:13 pm

Perhaps incorporating another solver might work, initially FreeCAD required ODE (Open Dynamics Engine.) It incorporates both a solver and collision detection, might be useful to you if you want to incorporate forces.
Need help? Feel free to ask, but please read the guidelines first
mk2
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Re: Animated 3D models of Steam Engines

Postby mk2 » Tue Dec 23, 2014 7:24 pm

Hello,

sounds like a case for MBD https://www.mbdyn.org

Multi body dynamics... Maybe you can save Time :-)


Kind Regards

mk2
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NormandC
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Re: Animated 3D models of Steam Engines

Postby NormandC » Wed Dec 24, 2014 1:49 am

It's GPL, which means it cannot be integrated with FreeCAD.
mk2
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Re: Animated 3D models of Steam Engines

Postby mk2 » Wed Dec 24, 2014 7:29 am

Hello,

Ok, i thought they are using the LGPL. Then look to the OpenModelica project please.

https://www.openmodelica.org

This project have a special self created license, but still for opensource and commercial software.


Kind Regards

mk2
romartin
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Re: Animated 3D models of Steam Engines

Postby romartin » Wed Dec 24, 2014 2:32 pm

microelly2 wrote:I bind the degrees of freedom to constraints which are controlled from outside by my adjustor objects. So the sketch is always completly determined and the solver has only to find the right solution.
I still have no idea what to do if the system is not solvable. Currently I hate ambiguous systems. An open problem is how to handle dead points: If you start the animation from the piston there are the two poles where the movement in reality follows the inertia but the sketcher solver can fall back too. so there is the need to bring physics (forces) into the system. but this is still far away.
Hi microelly2!
You wrote the above quoted phrase in response to an observation of mine that a model ready for animation might well have more than one degree of freedom. By this I meant that the animation of the model would allow independent incremental stepping of more than one of the constraints in one or more of the sketches. Your adjustor objects control the values of the sketch constraints that model the datums which represent these free variables. You express concern about unsolvable or ambiguous systems in which you may encounter cases like the dead point in which the adjustor may fail to identify the correct new value for a free constaint and you hint that maybe you'll have to introduce physical notions like forces into the model. This concern triggered a number of contributions which try to suggest ways of doing this using existing tools for simulations of physical systems.

Maybe I have completely missed the point of this text and of these other contributions.
Personally I think that you should keep your WB as simple as possible. I dont think anyone expects an Animation WB to understand a 3D model to the point that it can determine which are the free constraints and in which way their values should be moved or what are the physical forces and momenta in play. Information sufficient for driving an animation can easily be provided by the user together with the 3D model, the sketches and the mapping from the geometries in the sketches to the moving parts of the model.

Ciao, Ian
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bejant
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Re: Animated 3D models of Steam Engines

Postby bejant » Sun Jan 04, 2015 7:09 pm

romartin wrote:Thank you too bejant for recording the animation. Please teach me how to do this.
Ian
Hi Ian, I'm using Ubuntu now as my OS and that screen grab of your animation was done using Kazam. Back when I was using XP (up until just before MS stopped supporting it) I used Cam Studio to record.
http://camstudio.org/
http://sourceforge.net/projects/camstudio/

Before uploading the videos to a file sharing service I processed them through Handbrake in order to change them to MPEG-4 format (I think that's the format I used). The file size is then greatly reduced and it was still faster to run the Cam Studio .avi files through Handbrake to convert them to the more compact .mp4 file format in order to reduce uploading time, and I have a pretty fast internet connection.
https://handbrake.fr/
http://sourceforge.net/projects/handbrake/

It's not hard to do - probably much easier than animating your model!
romartin
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Re: Animated 3D models of Steam Engines

Postby romartin » Thu Jan 08, 2015 8:26 pm

Thank you bejant. I will try the Windows program you suggest.
Ian