Post Reply 
 
Thread Rating:
  • 0 Votes - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
[2.03 Public] Center of Mass jumps around - solved
2017-12-07, 07:12 AM (This post was last modified: 2017-12-07 01:41 PM by goduranus.)
Post: #1
[2.03 Public] Center of Mass jumps around - solved
Ever since a couple of years back I've been wondering why my crafts with all engines pointing through the center of mass would spin out of control.

Recently, while observing a moving VTOL craft in build mode, I've noticed that when the craft is moving, the center of mass actually flickers, even though the craft configuration hasn't changed, so that whatever thrusters that are pointing through the CoM, are actually not pointing straight through it any more.

The amount that the CoM moves away from its original position seems to be related to the speed of the craft, and looks to be lagging a few frames behind where the CoM should be. Tests with thrusters to see how the craft spins as a result of this also seems to confirm that the it seems to start spinning around what was its CoM from a few frames back.

I tried to take screenshot, but the CoM marker flickers too fast to be caught in the screenshot.

Attached is the craft in which I observed the CoM flickering. It has two thrusters, both of which point through the CoM when the craft is held static, and the CoM can be observed to flicker when the craft in moving while in Build Mode. It is most noticeable when the craft fires it's horizontal thrusters at 500m altitude.


Attached File(s)
.blueprint  Radar Satellite Fast2.blueprint (Size: 35.84 KB / Downloads: 10)

The original WW2 Lite Campaign, updated
Find all posts by this user
Quote this message in a reply
2017-12-07, 12:24 PM
Post: #2
RE: [2.03 Public] Center of Mass jumps around on moving craft in build mode
From my experience, it's not the CoM the problem, but the drag.
If the drag is applied higher than the CoM, then at low speed your plane will have a tendency to nose down as the drag will be negligible, but at high speed it will nose up because of the drag.

On a plane I had to add a few blocks in order to center the drag force enough so that the controls were strong enough to compensate both at low and high speed.
Find all posts by this user
Quote this message in a reply
2017-12-07, 12:45 PM
Post: #3
RE: [2.03 Public] Center of Mass jumps around on moving craft in build mode
(2017-12-07 12:24 PM)Gladyon Wrote:  From my experience, it's not the CoM the problem, but the drag.
If the drag is applied higher than the CoM, then at low speed your plane will have a tendency to nose down as the drag will be negligible, but at high speed it will nose up because of the drag.

On a plane I had to add a few blocks in order to center the drag force enough so that the controls were strong enough to compensate both at low and high speed.

I have seen the actual COM marker move, but that might be a visual bug only.

(2017-07-10 02:50 AM)Resolas Wrote:  Forward broadside is the best broadside
Find all posts by this user
Quote this message in a reply
2017-12-07, 01:40 PM (This post was last modified: 2017-12-07 01:46 PM by goduranus.)
Post: #4
RE: [2.03 Public] Center of Mass jumps around on moving craft in build mode
@Gladyon you might be right, I tried it with a completely cubical craft and there was no torque, even as the CoM went entire outside the craft's body.
So indeed it's probably a visual only thing like Kao said.

The original WW2 Lite Campaign, updated
Find all posts by this user
Quote this message in a reply
2017-12-07, 02:04 PM
Post: #5
RE: [2.03 Public] Center of Mass jumps around - solved
(2017-12-07 01:40 PM)goduranus Wrote:  @Gladyon you might be right, I tried it with a completely cubical craft and there was no torque, even as the CoM went entire outside the craft's body.
So indeed it's probably a visual only thing like Kao said.

IIRC markers are drawn on every update, physics are started on a separate thread on fixedupdate so you can't see the position of rigidbodies/transforms after the force is applied.
Even if markers were on fixedupdate, there's no way to wait for the physics thread to reattach with the updated body positions before the next run.
Find all posts by this user
Quote this message in a reply
Post Reply 


Forum Jump:


User(s) browsing this thread: 1 Guest(s)