A SERIOUS SURGICAL simulation!

[Charles]

Hi Julio,
How's it going about the elastic?
FYI, pay attention to the coronavirus, it could be almost anywhere nowadays.

[Julio Jerez]

Oh I have not touch the engine since last we were here, there has been lot of stuff going the the place I work and doing relocation of people around. So doing stuff after has not been in my mind.

I see if I can do it this weekend.

[Charles]

Oh I have not touch the engine since last we were here, there has been lot of stuff going the the place I work and doing relocation of people around. So doing stuff after has not been in my mind.

I see if I can do it this weekend.

Understand, that's all right.

[Charles]

Hi Julio,

Would you have time this weekend to help me with the elastic of the rod? We are really close there.

[Julio Jerez]

ok, I made the demo using custom spring/ damper

I reverted the changed that I made to the stock ball socket and implement the funtionality in teh
dFlexyPipeSpinner joint.
there is no reason to mak ethe base joint more complex for a unique funtionality when we can subclass the joint and make anyway we want. beside you knwo hwo to add that kind of funtionality.

anyway the funtion you should look at is
void ApplyElasticConeAction(const dMatrix& matrix0, const dMatrix& matrix1, dFloat timestep)

the spring/ damper and relaxation hard code tweaked until the look right. you can make them expose to the gui interface.
in general a spring damper onel has tow parameter, but here we have three: damper, spring and relaxation.
I will explain the theory of hwo the come about later today if you are interested in knwo why is this.

anyway of you sync and try teh demo tell me is this is better.

[Charles]

Thanks Julio, glad to see you are here, I will try that.

[Charles]

Hi Julio,
What do you think of the physics engine market? The PhysX and Havok are open source now, how can the others survive such as Bullet, Project Chorono, IBM, SOFA etc?

[Dave Gravel]

All physic engines are different but can do similar things it depend more on the tools and features and the users utilisation.
If the creators or contributors do it only for money maybe they is better to start to think differently or use existing solutions.

In my mind when you do a physic engine it is more by passion that a money historia. The goal is more about learning and search on how reproduce real life behaviors.
If a physic engine is make only for money it is at risk to have a lot of lack about real physics representation.

They is surely better to think to make money with the final result from what the engine can do and show.

In a physics engine the speed and the objects count is not always the best factor of success.

[Charles]

In my mind when you do a physic engine it is more by passion that a money historia. The goal is more

Glad to here from people.

One is very lucky if he or she is motivated by passion. Could you share some more deep details about these industry?

Oh, a tech question, how can you keep a rod move inside another rod ensuring that , the inner one is never goes out of the outer one ?

[Charles]

Hi Julio,

I want one rod move inside the other one. The old method i use is that using colliders. But in real application environment, this method works not well.

So i use constrain method. Constrain the inner rod always move along the center line of the outer rod.
I add following code in the "SubmitConstrains" of "BallAndSocket" class.
https://drive.google.com/open?id=18N9rV ... mJHMNvNKfh

It works but with problems. Seems have conflicts with origin constrains:
https://youtu.be/dQCKrqC2BH4

Could you please provide any idea to solve this?

[JoeJ]

Could you please provide any idea to solve this?

Quickly looking at your code i see you set velocities inside constraint callback.
This seems wrong, because the constraint solver solves for forces based on your set target acceleration, and velocities are calculated from that internally and then integrated.

So if you want to set velocities directly, you don't need a constraint for this.

There was a custom joint demo, where Julio made a rollercoaster with bodies constraint on a bezier spline, this might be a nice template for you. But if it is no longer activated in the demo sandbox, you could look up older versions of Newton to find it with some luck.

I did not follow this thread and are not sure what you try to do. (I'm confused if you try to constrain along a known fixed path, or to keep inside a lesser strictly defined shape of an human organ.)

I hope Julio is well and can reply himself...

[Julio Jerez]

Hi guys.
I was out of commission for a while because a very serious health problem. I even was on intensive care for four days. But I recovering now.
This was not the virus, but given how crazy thing are now it made far more dramatic.

Anyway, I see if I can read the thread and answer some questions.

[JernejL]

It is good to hear that you are feeling better! I wish you a good and speedy recovery!

[Slick]

Good to hear that you are back. All the best.

[Sweenie]

Welcome back Julio. Good to hear you're ok.