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ACrab Balance - How!?
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Author:  Denninja [ Fri Jul 27, 2012 6:34 pm ]
Post subject:  ACrab Balance - How!?
My ACrab doesn't want to stay upright!
Just falls over on the side when touching the ground.
What attachments should I keep the Mass on?
Maybe add a 1-pixel attachment with high mass dangling at the bottom?

It has a few large attachments around the core, one turret, and legs a tiny bit larger than Big Crab's.
Author:  xenoargh [ Sat Jul 28, 2012 5:59 pm ]
Post subject:  Re: ACrab Balance - How!?
Big issue is the center of mass.

Main body should weigh considerably more than anything else. Legs should be kept really light. Do not give a lot of weight to the HDFirearm, as its center of gravity is offset from the main body.

Easiest debug solution is to give everything but the main body a mass of 0.00001 and then gradually work it back up.
Author:  Coops [ Sat Jul 28, 2012 6:07 pm ]
Post subject:  Re: ACrab Balance - How!?
I had the same problem before, actually.

Just give the main torso a lower offset (or centre of mass) than where the legs attach and it should stay upright.

No need to tinker around with the mass of everything.
Author:  xenoargh [ Sat Jul 28, 2012 6:19 pm ]
Post subject:  Re: ACrab Balance - How!?
Ideally, you should be able to keep the balance no matter where the offset is; the issue there is mainly the length of the strides, and, in theory, the walkpath can be used to keep it stable.

That said, the engine expects ACrabs to fit within pretty narrow parameters, with the center of mass really low and the leg IKs positioned above the center of the hip. Even one pixel is a major difference.

Fact of the matter is, if you want taller ACrabs that don't have stability issues, you pretty much need to do it via Lua, like I did. I should probably make a tall, long-legged ACrab to demonstrate.
Author:  Denninja [ Sat Jul 28, 2012 10:35 pm ]
Post subject:  Re: ACrab Balance - How!?
xenoargh wrote:
Fact of the matter is, if you want taller ACrabs that don't have stability issues, you pretty much need to do it via Lua, like I did. I should probably make a tall, long-legged ACrab to demonstrate.


I'd like to know how to edit the walkpath variables for larger legs too :D
AddSegment specifically.

The crab has weird balance! It keeps tipping forward even though only the main body has mass and I lowered it's position.
Sometimes it clips through Dirt, falling until it hits Cement or Metal, and then it clips through some.

This is the material the armor (almost all of the body surface) is made from:
Code:
   Bounce = 1.2
   Friction = 0.3
   StructuralIntegrity = 90000
   DensityKGPerVolumeL = 1
   GibImpulseLimitPerVolumeL = 90000
   GibWoundLimitPerVolumeL = 90000
   Priority = 5


Here's my ACrab in the process of walking on it's toes while tipped around 45 degrees forward, facing the left.
Image
Author:  No_0ne [ Sun Jul 29, 2012 4:49 am ]
Post subject:  Re: ACrab Balance - How!?
The SpriteOffset needs to be lower than where the legs attach to the body, otherwise it will be prone to tipping over.
Author:  Coops [ Sun Jul 29, 2012 5:43 am ]
Post subject:  Re: ACrab Balance - How!?
Don't bother, No_0ne.

I already mentioned that but they wont listen.
Author:  Denninja [ Sun Jul 29, 2012 6:20 am ]
Post subject:  Re: ACrab Balance - How!?
Coops wrote:
Don't bother, No_0ne.

I already mentioned that but they wont listen.


I did exactly that! The main body is below the leg attachment, it's just behind the curved part.
I then also tried shifting all mass to an attachment far below everything, and it still tipped over the same way.
Author:  Coops [ Sun Jul 29, 2012 6:26 am ]
Post subject:  Re: ACrab Balance - How!?
The offset is?

Or the actual physical sprite?

Theres a large difference between the two, the offset determines the center of mass whereas the position is just a graphical and physical thing towards simulation.
Author:  Denninja [ Sun Jul 29, 2012 6:36 am ]
Post subject:  Re: ACrab Balance - How!?
Coops wrote:
The offset is?

Or the actual physical sprite?

Theres a large difference between the two, the offset determines the center of mass whereas the position is just a graphical and physical thing towards simulation.


My bad! Looks like I had the offset for the legs sprites set too negative...
So the attachment offset wasn't what it appeared!
I set that to 0 so the leg attachments now fit a lot higher.
It's now 12 above the body center.
Thanks! :)

But... now I've got a problem that couldn't be seen with the tipping bug active...
The legs clip through the ground. >_<
They're made of the same material and mass as the larger body parts, yet those don't clip through.
Author:  The Chairman [ Sun Jul 29, 2012 5:08 pm ]
Post subject:  Re: ACrab Balance - How!?
Try reducing the overall weight of your ACrab, maybe that helps.
Author:  xenoargh [ Sun Jul 29, 2012 8:00 pm ]
Post subject:  Re: ACrab Balance - How!?
Quote:
The legs clip through the ground.
Correct the foot offsets, and make sure that the foot AtomGroup has enough surface area for the mass.
Author:  Denninja [ Mon Jul 30, 2012 4:33 am ]
Post subject:  Re: ACrab Balance - How!?
xenoargh wrote:
Quote:
The legs clip through the ground.
Correct the foot offsets, and make sure that the foot AtomGroup has enough surface area for the mass.


TIL It's time to learn that.
Thanks much, I'll be done here now. :D
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