best way to implement mechanical articulations

best way to implement mechanical articulations

Hi All

I am trying to achieve a mechanical piece that can be animated correctly.

Basically this is what i am doing: I have abox and a cylinder that are coupled together; the box has a prolonged polygon that goes inside the cylinder, and act as point of rotation for the articulation.

I've attached the picture, they will be more clear than my description for sure anyway is similar to the arm-forearm articulation at the elbow.

Now these are the issues that i have, and before going forward with the modeling part, i want to get it right, so when i will rig it, i will not have to curse myself for not doing things in a different way

1) to simulate the rotation, i can rotate the cylinder, but it always rotate using the center of the object, is there a way to change the pivot point for the transform tool? When i will add the bones it will be different, but now without bones i have problems to imagine how it will work if it rotate using the center of the object as pivot point

2) how would you approach the rigging phase? I am trying to make different parts and put them together; to avoid to have bending and other weird effect, that should not happen on mechanical parts; plus is possible to limit the range of a specific movement, to avoid that the polygons will intersect and take away the realism?

Thanks in advance!

Hi!
to change the pivot point go in "pivot" mode and move it wherever you want it to be (right click + customize toolbar to place the item into it if it's not there already...)

for the rest if you search the forum you will find some good threads discussing the same problems, here's one for example (francois is one of our best "mechanical animators")

cheers,
Alessandro

Hi,

darshie76 said:

... i want to get it right, so when i will rig it, ...
... When i will add the bones it will be different, ...
... how would you approach the rigging phase? I am trying to make different parts and put them together ...

Click to expand...

Depending on what you want to achieve, rigging (using bones) may not be necessary. Please have a look at the examples in these threads to get some ideas :
- 4-bar animation
- bolt cutters
- mechanical animation
- mechanical movements
- simple mechanical animation


Alessandro,
:redface: ... :wink:

Thanks !

I had no idea that there was a pivot tool now would be interesting to see it in the help, and also understand how to get out of pivot mode, since when i click on transform it won't change to transform but stays in pivot mode

Sorry but i didn't realized that there were so many examples; guess gotta search better before bothering others

IS anyone able to explain in very few words the basic concepts related to these examples? I do not need a step by step tutorial, but just a sparkle to start

basically i see terms like IK and joints; and i am not familiar exactly how these can be related to mechanical pieces (i know IK from poser, and from what i get is a way to control limbs so one movement affects the root and back); since to me they are abstract concepts that i see and use in various 3d software, but i've never had the chance to learn how do they work, and mainly for human body (that per se is a wonderful example of mechanical engineering).

I do not need to simulate forces, pulleys and similar, but just make articulations that would be believable in a mechanical context (the piston example is as close as i wanna get); and all that i have to learn is

-put pieces together and set a limit on how much they can rotate on each axis

-simulate a nut and bolt, so when i move a piece i don't get the "flying limb" effect that happens in poser, when you lift a leg and the knee bend right and then goes in the opposite direction (that uses IK)

Once i get the basic to execute these actions, i can just learn how to do it by myself so any pointer to concepts and very few words about how to achieve these goals is more than welcome

I hope also to see in future releases of Cheetah3d, some tool that would nicely add a nut and bolt to 2 pieces of choice

Thanks!

Darshie,
I suppose you're entering in pivot mode by clicking its icon in the toolbar, right? to get out of it just go into any other mode (point/edge/poly/object) using their toolbar icons as well... (it's a Mode, not a Tool... that's why you're not getting out of it calling another tool)

for the rest, you have to wait for françois or somebody else I'm afraid (still have to go into mechanical thingies... but I will one of these days)

cheers,
A

"IS anyone able to explain in very few words the basic concepts related to these examples? I do not need a step by step tutorial, but just a sparkle to start"
I'll be watching this thread. I saw and downloaded all the examples and all I could do was watch the animations in a daze. Can't get my head around what was going on even after studying the files. Duh!:redface:

SurfingAlien said:

Darshie,
I suppose you're entering in pivot mode by clicking its icon in the toolbar, right? to get out of it just go into any other mode (point/edge/poly/object) using their toolbar icons as well... (it's a Mode, not a Tool... that's why you're not getting out of it calling another tool)

for the rest, you have to wait for françois or somebody else I'm afraid (still have to go into mechanical thingies... but I will one of these days)

cheers,
A

Click to expand...

I see i have moved it into the tools area, not into the mode area, so was not sure why would not switch *slap his forehead*

uncle808us said:

"IS anyone able to explain in very few words the basic concepts related to these examples? I do not need a step by step tutorial, but just a sparkle to start"
I'll be watching this thread. I saw and downloaded all the examples and all I could do was watch the animations in a daze. Can't get my head around what was going on even after studying the files. Duh!:redface:

Click to expand...

Is not that hard but learning is a different process for every of us.

I don't do well with step by step tutorials, because i do not learn how does it works, but just how to do one thing, and is hard to implement then in other cases or situations.

While when i get the point on the concept, and then i see a practical application, i am able to adapt the concept to what i need, because i know what the capabilities of a tool/feature/object are, and i can use it for what it is made for

In programming, when you get a sample is pure gold! Because you can see how something was implemented, but this assume that you know what the parts of that functions are, and how they work; so i guess that you cannot get fully enlighten by the example since you lack the knowledge to understand how it works (and so do i LOL)

I am a programmer and not a 3d artist, so this works for me; but maybe others like to have the step by step since they are not programmers and are more visual persons than conceptual persons ^_^

I will be more than happy to write a step by step in my weird English, as soon as i grasp the concepts (guess that i gotta start all over with the C3d training DVD), hopefully

Hi,

uncle808us said:

"IS anyone able to explain in very few words the basic concepts related to these examples? I do not need a step by step tutorial, but just a sparkle to start"

I'll be watching this thread. I saw and downloaded all the examples and all I could do was watch the animations in a daze. Can't get my head around what was going on even after studying the files. Duh!:redface:

Click to expand...

Other than taking one of the examples and explaining it line by line, I really don't know what to do to give you the needed sparkle ! Almost everything I know is in these samples.
Please keep in mind that Cheetah3D is not designed at first to do these kind of things (I can give you some names of perfect applications for this but be prepared to pay the bill !) However, with a good understanding of it's powerful tools/functions, there are ways to fake mechanical functions. So, playing / practicing with the various tags is important to understand how they react and that's what I have been doing just like others with eg. the material system.
So, go ahead and choose one sample and I will try to dissect it as much as I can to explain it

Francois; can you put a couple of sentence down regarding how to put together 2 simple objects?

Something like 2 parallelepipeds joined at one end?

That would be a good start In the meantime i have noticed that the DVD for C3d v5 is kinda lacking on some of these concepts...there is 1 short movie related to bones and joints on a skeleton, while the tags section says nothing about put together objects.

I love the training dvd, but honestly it lacks of many things that takes a lot of time to find a solution (some are happy to experiment, i have a tight schedule in my life, and i would like to learn instead of doing trial by error ) Hopefully someone will do something other than the standard lessons that are the same for every software.

Hi.
I´m still not sure if you´re really in the need of "advanced" mechanical stuff - or a "simple" hierarchy set up will work for you.
Here´s an basic example of what I was trying to say. You can zap through poses and run a quick animation.

Cheers
Frank

Hi,

frank beckmann said:

...
Here´s an basic example of what I was trying to say. You can zap through poses and run a quick animation.

Click to expand...

Thanks for your help, Frank. Nice example too !

darshie76 said:

Francois; can you put a couple of sentence down regarding how to put together 2 simple objects?
Something like 2 parallelepipeds joined at one end?
That would be a good start

Click to expand...

I didn't think that I would have had to hold your hand at that level ... :wink:
See corresponding images
1) Create a box and shape/scale it as a bar. Make it editable and burn the transform
2) Duplicate it and move/rotate the copy to the end of the original bar
3) Switch to Pivot mode and move the pivot to the end of the bar.1 (notice that the pivot tool is slightly bigger than the select tool and the tips are shaded). This pivot point is your "nut/bolt"
4) Now you can rotate your bar just like if there was a nut/bolt
5) To physically attach the 2 bars, move box.1(bar.1) as a child of box
6-7) If you now rotate the original box, box.1 will follow

As Frank demonstrated in his example, you can now add a pose tag to Box and record several positions of these 2 bars. Don't forget to have the "Key hierarchy" switch ON.

Awesome!

Will take some time tomorrow to get into it, but it looks exactly the kind of info that I was looking for