Inertia problems

[Aldeminor]

Thanks all And what about custom physical meshes? For example, we need to realise complex body with cavities and deepenings, such as big space cruiser, and want to correcly process all colisions with smaller objects. As I know, NGD creates its own "physical mesh" based on highest points of original 3D-object. How to avoid this?

[JernejL]

You can build a complex concave compound collision made of convex objects, decomposing a ship mesh model into concave pieces can be also done with a proper library.

Here is a example of a spaceship for a prototype game engine i made, it's used on wiki as example shape for compound collision:

[Aldeminor]

Thanks all, guys! Answears is very useful, still working on a project!

[Aldeminor]

Another strange situation - why the angular speed increases when decreases object scale? Turning forces and body mass are unchanged, just scaling object and taking strange effect...

[JernejL]

What do you mean? your question is very unclear.. are you using very small objects and are experiencing integrator problems?

[Aldeminor]

Trying to explain We have an object with its constant mass and applying torque to it. All is okay, object turning. Then scaling it down (without changing mass) and again applying same torque - object turning faster. And vice versa - scaling object up and its turning slower with same torque.

[Aldeminor]

Another one interesting moment. After applying torque to the body it has rotating by inertia with attenuation, slow down and eventualy stops. But there are small non-zero angular speed value when body reaching it stops too sharp. How to regulate this limit?

[Julio Jerez]

There was a bug related to that and I fixed in 2.24, get that version (by editor the download link because it is not ready yet)

[Aldeminor]

Thanks for fast reply, Julio!

[Aldeminor]

We are download 2.24 version, but it's still has a problem with small values of torques and forces. What we could do wrong?
Also, dll's in 2.24 signed as 2.23

[Julio Jerez]

but what is the problem you have, I do not knwo what you mean small torque.

I beleive the inertia is just fine,
you go me all confused, you speak abut simulating Planets, and space tuff and then you speak of small torque, I do not know what you are doing.

[Aldeminor]

Look at tech-demo:
http://file.qip.ru/file/GxxS_K5n/arhivchik.html (download this)
http://file.qip.ru/file/pNR9w5Tt/arh2.html (and then replace files)
Launch PhysicSample.exe
The ship is not reacting on small amounts of forces applying to it, and when rotating, it stops too sharp.
Controls - qewasd, 1-9 is throttle, arrows or right click to mouse control. Use mouse, you will understand what I mean.
PS: Sorry, forgot one dll: http://file.qip.ru/file/0rPLZ736/MTV3D65.html
Place it in Debug directory.

[Julio Jerez]

Ok I just download this and I see what you mean, that look like a big bug, but I do not think this is relate to Newton, as I never seen anything like that in newton.
It is amost like sonethong is clamping the velocity to zero when it reach some small value plus snapin teh position to some king of center.
Anythong liek that will bring compltere caos in a simulation with many resting bodies.

can you post here the Force and truqe call back code you are using to move the ship.
also are you using any joint to mopve teh ship?

anyway I will debug tonigh to see if I can see what it is.

[Aldeminor]

can you post here the Force and truqe call back code you are using to move the ship.

Our programmer said all source code are included in archives. He can cut up what you told few hours later, I'll post it.

also are you using any joint to mopve teh ship?

No, just straight applying forces to body.
And this terrible effect also appears even if we set angular velocity, without torques - ship stops turning at near zero speed.

[offtop]
Julio, can you post link on fullsize logo of Newton? We want to place it in the bootscreen of our project

[Julio Jerez]

No, just straight applying forces to body.
And this terrible effect also appears even if we set angular velocity, without torques - ship stops turning at near zero speed.
[offtop]
Julio, can you post link on fullsize logo of Newton? We want to place it in the bootscreen of our project

Ok I will check it out tonight.

the logo is in the FAQ part of the forum