Hi there, I would like to use framsticks to make realistic-looking
creatures, and one of the issues I have to figure out is the size scaling of
the physics. How big are framsticks creatures? This has a meaning with
regard to the way other physical forces work: if we're looking at a scene
from an extreme closeup, the physics look different than if we're seeing an
object that looks the same size on the screen but that is actually being
viewed from a distance. So a spider can survive a fall off the equivalent of
a 30 story building.
So I'm trying to get a handle on the scaling of framsticks, if they move
more like very small creatures or very large ones. Is there any way to match
the units used in various parts of framsticks to units in the real world?
Like taking just gravity to start with: is a gravity setting of "1" (so
gravity cannot go to unusually high levels?) the equivalent of 9.8 metres
per second per second?
Daniel Saunders
Re: Scaling of physics
> So I'm trying to get a handle on the scaling of framsticks, if they move
> more like very small creatures or very large ones. Is there any way to match
> the units used in various parts of framsticks to units in the real world?
> Like taking just gravity to start with: is a gravity setting of "1" (so
> gravity cannot go to unusually high levels?) the equivalent of 9.8 metres
> per second per second?
Regarding physics, starting with Framsticks v3 there is the well-known
ODE engine included (www.ode.org) as an alternative to MechaStick.
macko
Re: Scaling of physics
Daniel Saunders wrote:
[...]
> more like very small creatures or very large ones. Is there any way to match
> the units used in various parts of framsticks to units in the real world?
> Like taking just gravity to start with: is a gravity setting of "1" (so
> gravity cannot go to unusually high levels?) the equivalent of 9.8 metres
> per second per second?
the framsticks simulator is not meant to be accurate. it was created
without any relation to the actual space and time dimensions. there is
even no "standard" simulation speed...
however, it simulates the well known physics laws, so it is definitely
possible to calculate the scale.
for example, the food created 11 units above the ground (by "Drop food")
needs 75 simulation steps to reach the ground (under standard gravity
conditions).
x=0,5*g*t^2
g=10 [m/s^2]
x=scale*11 [m]
t=speed/75 [s]
speed =~ 50/sqrt(scale)
scale =~ 2500/(speed^2)
examples:
speed=10 steps/sec, scale =~ 25m
speed=50 steps/sec, scale =~ 1m
scale=0.2 m (20cm), speed =~ 113 steps/sec
scale=0.05 m (5cm), speed =~ 226 steps/sec
by reducing the gravity settings you can increase the steps/sec needed
for a given scale (or decrease the scale for a given speed).
for example, when gravity=0.25 the "realistic" speed for scale=25m is 40
steps/sec - which means more accurate simulation and more rigid joints.