JoeJ wrote:But having many multibody spaceships is a interesting problem.
I would handle this with a LOD system: Collapse distant ships to a single compound body. As you get closer and few / single ship(s) comes to focus, switch to them to multibody representation. The switch should go unnoticed if you do it correctly.
Oh Joe that's was what I was trying to say before with my poor English.
basically most people do not know how to make a mathematical model to simulate some part for a problem.
I ask him to tell me of his model was a large mass with some body parts, or if it was like a space station with many body parts. because this determine the approximation that can be made.
I want to write a tutorial for how to do this with some example because it has gone for too long.
I was thinking of a airplane, because is a case when the body is no subject to collision forces, but space sim is even better.
for example, a space sim can be simulated entirely with compound collision. and eh case that worry you that is the body part move the COG change and that can case hitches, that where math comes in.
say the space ship is a compound collision made of a series of Collison shapes.
and some of these shapes have relative movements
the second law say
F = m * a;
we now see the flaw there, that equation does not account for the mass changing, for thet we go to the more basics from, for equal to the change of momentum
F = d(m * v) / dt
if in the space ship the mas is changing, now we get
F = d (m) / dt + m * dv / dt
m * a = f - d(m) / dt
now the equation is the next force actin on the center of mass plus the rat of change of the mass with time.
remember when I said if we can a vehicle where the moving part as small compere to the mass of the vehicle the d(m) / dt can be neglected
so a model for a small space ship can be represented by F = m * a
a mode for a space station dm / dt is significant and we nee another equation.
for that we can write the expression for the center f mass and write
dg = m1 + m2 +,,, / n
we can write the mumerical equation fro the kinematic motion of each body part because each body part is a rigid body.
CG* m1 = m1 * function (x)
where function of x is some rotations extruded by the joint relation (0)
you can now apply the rule of change and get the rate of change of m1 as a function o fit position and angular velocity
dm / dt = (dm / d0) * (d0 / dt)
but dO / dt is the angular velocity W of that body part,
the rate of change of (dm / d0) may be a constant or it can even be a magic value, K
now we can plug that ito the equation and we get
m * a = F - K1 * W1 - k2 W2 + ....
the terms K1 * w1 are correction factor that are zero when body part is no moving and compensate for the center of pass when there are moving
I know It sound exoteric, but this is how more or less physics and mathematical write model to simulate some objects.
so yes you can model large objects like a air craft carrier, a space station or a 747 made of connected parts that that have motions like vibration, of flex under there weight, stuff like that.
and it call plug into a general physics engine.
it is hard to start with a body with large moving part, is better to start with a small vehicle and build for there.
here is the cool part, by doing this you can make the model are realistic as you can or as arcade as you can base of what you neglect of not.