FORMAT OF WORLD & SEQUENCE FILES
--------------------------------
AERO data files are user-readable ASCII files. Comments start with a
hash mark ("#") and extend to the end of the line. Lower case characters
denote an optional value and need not be specified - in this case the
default values (often 0) are used.
STATE FORMAT
Z # begin of a new state
t <starttime:real>
g <gravity:vector>
s <seed value for random value generation:integer>
# any number of bodies
K<bodynr:+integer> <bodytype> <body geometry> <material>
m <mass:real> # mass in kg
p <position:vector> # position of the center of gravity in meter
v <velocity:vector> # in meter per second
a <acceleration:vector> # [m/s^2]
q <quaternion> #
w <vektor> # rotary velocity [rad/s]
u <vektor> # rotary acceleration [rad/s^2]
c <red:ushort> <green:0-65535> <blue:ushort> # color
n <transparency:real> <reflexion:real> <roughness:real> # for ray tracer
b -[g][m][k] # type of movement: no gravity,
# no mass, no collision check
i <idnr:long> # identification nummber
For a "composed" body, the corresponding embedded bodies with their
parameters should be following the body definition.
The position of the composed object is computed as the center of gravity of
the embedded bodies!
E <bodytype> <geometry> <material> # only cuboid, sphere and cylinder are allowed
m <mass:real> # mass [kg]
p <position:vektor> # position [m]
q <quaternion> # quaternion ref. Inertialsystem
c <red:ushort> <green:ushort> <blue:ushort> # color
X # end marker of a composed object
Links are entered as follows:
V<linknr> K<nr1> K<nr2> <linktype> <linkparameters> # any number of links
a <linkpoint1:vektor> # position of connection at body <nr1>
b <linkpoint2:vektor> # and at body <nr2>
A constant force of <strength> is applied at a point of a body during the
time intervall t0 and t1.
F <t0:real> <t1:real> K<bodynr> [<point:vektor>] <forceparameter>
Q # denotes the end of the current state
For all definitions above, the following types apply:
long = 0..2^31
ushort = 0..65535
vector = <real> <real> <real>
quaternion = <real> <real> <real> <real>
bodytype = sphere | box | cylinder | plane | nail | mpoint | point | composed
bodygeometry of "sphere" = <radius:real>
bodygeometry of "cylinder" = <radius:real> <height:real>
bodygeometry of "box" = <xyz-dimensions:vector>
<material> = material name from the material table e.g.: iron, plastic, ..
# this is only set for sphere, box, cylinder und plane !
<linktype> = spring | damper | joint | rod
linkparameter for "spring" = <resting length:real> <spring constant:real>
linkparameter for "damper" = <damping constant:real>
linkparameter for "rod" = <length:real>
<forceparameter> = inertial <force:vektor> # const. force in inertial system [N]
<forceparameter> = local <force':vektor> # force ref to body coord. system
<forceparameter> = guided <force:real> K<targetbody> [<target position:vektor>]
# constant force in [N] directed always to a point at the target body
The following samples show erroneous entries, which will be checked
when read by AERO:
* Z
* g 0 -9.81 0 # negative gravity
*
* K1 box 0.1 0.2 0.3 iron # iron cuboid falls down to nowhere
* v -1.0 0 0
*
* K2 sphere 0.05 plastic # plastic sphere as pendulum
* p -2.0 10.0 0
*
* K3 nail
* p 0.0 10.0 0.0
*
* V1 K2 K3 rod 2.0
*
* F1 K1 0 1 0 0 0 inertial 10 0 0 # force in the center of K1 in x-diection with
* # strength 10N is applied during time 0s <= t <= 1s
* Q
MATERIAL FORMAT:
# this is an remark
M <maximum number of materials:Integer>
m <name:string> <density:real> <dynamic friction constant:real>
<static friction constant:real>
<impact value:real> <spring value:real> <damping value:real>
[<default_red:ushort> <default_green:ushort> <default_blue:ushort>
<transparency:real> <reflexion:real> <roughness:real>]
# density in [kg/m^3]
# transparency in the interval 0..1
Q
CONFIGURATION FORMAT
P
h <integration step width:real> <min> <max>
e (Y|N) <eps:real> # error control Y(es) or N(o)
k (Y|N) <collision step width:real> # collision activated Y(es) or N(o)
b <max. resting speed:real> <min. penetration depth:real>
u <min. sliding speed:real> <min. rolling speed:real>
g (Y|N) <random gravity in %:real>
r <rod spring constant:real> <rod damping constant:real>
j <joint spring constant:real> <joint damper constant:real>
m <minimal srping stretching:real>
q <maximal cuboid-collision diagonal depth:real>
s (Y|N) # spring impact YES, NO
a (Y|N) <cw-value of sphere:real> <cw-value of cuboid:real> <cw-value of cylinder:real>
Q
The AERO internal format is now described by using an example.
Sample world (state) file:
W # start world file
M 32 # material table, may contain 32 entries
# two materials, "iron" and "wood" are entered
m iron 7.8000e+03 1.0000e+00 1.3000e+00 9.0000e-01 5.0000e+04 5.0000e+02
m wood 6.0000e+02 5.0000e-01 6.5000e-01 7.0000e-01 5.0000e+04 5.0000e+02
Q # end of material table
Z # start description of current state: objects, forces, and links
t 1 # time of state description
g 0 -9.81 0 # gravitation vector
# object definitions start with letter "K" plus a number
# "K1" is the first object: sphere, radius 5cm, material iron
K1 sphere 5.00000000e-02 iron
# mass
m 4.08398627e+00
# position
p -2.14595881e-01 8.11705112e-02 0.00000000e+00
# orientation
q 6.61532809e-01 0.00000000e+00 0.00000000e+00 -7.49916216e-01
# velocity
v -1.54115612e-03 1.68088549e-03 0.00000000e+00
# rotary velocity
w 0.00000000e+00 0.00000000e+00 1.72884763e-02
K2 nail # object labelled "K2": immmovable point (nail)
p 0.00000000e+00 4.00000000e-01 0.00000000e+00
# link definitions start with letter "V" plus a number
# "V1" links objects K1 and K2 with a rod of specified length
V1 K1 K2 rod 3.26810113e-01
# the following line(s) denotes the link's fixture point for
# the first and/or second object (marked "a" or "b"), in case
# it is not identical to an object's center.
a 3.75000000e-02 -4.00000000e-02 0.00000000e+00
V2 K1 K2 rod 4.12310563e-01
# the second link "V2" is again between object K1 and K2
a 3.00000000e-02 4.00000000e-02 0.00000000e+00
b -5.50000000e-01 -3.12250226e-17 0.00000000e+00
# force definitions start with letter "F"
# next params: start and termination time for applying force
# next params: object (here "K1"), force type (guided,
# inertial, or local), force attack vector (includes strength)
F 1 1.01 K1 inertial 0 0 4
Q # end description of current state
# end of world file
Sequence files are similar to world files, however, they may conatain several
"world" states. For these, a mark "X" has to be placed before the first state,
and a mark "Y" has to be placed after the last state.