**Damage model in flt-files
          • by Andy** * 28.03.2003 *

This is a short guide on how to edit the aircraft's Damage Modells of the flight simulation 'European Air War' by Microprose.
I'll use Chris Coon's original flt-file code to make some comments on how the damage modells for EAW aircraft can be altered to get them more realistic.

At first a general note: Please get Alessandro Borges' '3DZ! Studio' first. You will need it to locate positions of hitbubbles and other important points of the aircraft's frame. Further more you will need a Hex-Editor to make changes to the flt-file, you cannot do all changes with Aircraft Edit because the meaning of many bytes was still unknown when it was released.
Ok, lets start:

Most coordinates especially these of the hitbubbles, gun tracers and other important points are set in feet. That means we can simply read the 3dz coodinates with '3dz! Studio' and convert them to feet. This is possible because of Anthony's very valueable work to determine the scale of EAW.
To convert the 3dz coordinates to feet you have to multiply them with a factor of:

-0,14708723

Pay attention to the sign! Don't forget it.

A little example: The 3dz-y-coordinate of the Ju 88A's left wingtip is -227. Multiply it with the factor mentionned above and you get +33,4 feet. BTW: the wingspan of the real Ju 88 A-4 was about 66 feet. So this value is quite close to reality. ;o)

/
.flt file format

As you know the flt-files contain the info on the Flight Modell and on the Damage Modell. I'll simply make comments at the positions that are relevant for the DMs. You can easily indentify these lines because I added the byte offset at the beginning of the line. All other code given below is needed for the Flight Modell. Get 'Knegel's' and mine notes on the Flight Modell if you are interested in it.

typedef struct fm_aero_type_data
{

engine data
short engine_count;
short engine_type;
float engine_alt;
float engine_slope_low;
float engine_slope_high;
float max_prop_np;
float min_throttle;
fm_control_data dT; Throttle control
{float max;
max position
float min; min position
float rate;
rate of change
}fm_control_data de; elevator
{float max;
max position
float min; min position
float rate;
rate of change
}fm_control_data df; flaps
{float max;
max position
float min; min position
float rate;
rate of change
}fm_control_data da; aileron
{float max;
max position
float min; min position
float rate;
rate of change
}fm_control_data dr; rudder
{


float max; max position
float min;
min position
float rate; rate of change
}


performance spec
float max_alt;
float max_vel;
float max_alpha;
float critical_mach;
float max_g;
float min_g;
float wing_y_mac;


inertial data
float mass_empty;
float mass_fuel;


float inv_Rx;
float inv_Ry;
float inv_Rz;


float Izy;
float Ixz;
float Iyx;


stability coefficient
fm_aero_coefficient coefficient;
{

drag stability derivatives
float X0;
float XL;
float Xdf;
float XdT;
float XG;
sideforce stability derivatives
float Yb;
float Yr;
float YdT1;
float YdT2;
float YdT3;
float YdT4;
float Ydr;
float Yda;
lift stability derivatives
float Z0;
float Za;
float Zad;
float Zq;
float Zde;
float Zdf;

roll stability derivatives (x)
float Lb;
float Lp;
float Lr;
float Lda;
float Ldr;


float LdT1;
float LdT2;
float LdT3;
float LdT4;


pitch stability derivatives (y)
float M0;
float Ma;
float Mad;
float Mq;
float Mde;
float Mdf;

yaw stability derivatives (z)
float Nb;
float Np;
float Nr;
float Nda;
float Ndr;


float NdT1;
float NdT2;
float NdT3;
float NdT4;


}

fm_lookup_table aX0; tables for interpolating values between zero_x and (zero_x + delta_x * table_size)
{long table_size;
float delta_x;
float inv_delta_x;
float zero_x;
float aTable[10];
}fm_lookup_table aZa;
{long table_size;
float delta_x;
float inv_delta_x;
float zero_x;
float aTable[10];
}fm_lookup_table aEe;
{long table_size;
float delta_x;
float inv_delta_x;
float zero_x;
float aTable[10];
}fm_lookup_table aAe;
{long table_size;
float delta_x;
float inv_delta_x;
float zero_x;
float aTable[10];
}fm_lookup_table aRe;
{

long table_size;
float delta_x;
float inv_delta_x;
float zero_x;
float aTable[10];
}

weapons data
fm_weapon_data aWeapons[6];
{fm_vector3 position;
{float x;
float y;
float z;
}


float secondary_pos_x;
float secondary_pos_y;
float muzzle_velocity;
float rof;
float dispersion;
float eject_pos1;
float eject_pos2;
short muzzle_id;
short duration;
}


byte offset

landing gear

035C float land_height; height of main gear (feet)
0360 float land_pitch;
angle of pitch when standing on ground (rad ---> 360°=2Pi)

I'm not sure what these values are good for. Somehow the land_height seems to be the height of the landing gear when the plane is placed on the ground. As soon as you start the engine the byte values starting at offset 0370 are used. Land_pitch can be easily calculated with x- and z-coordinates that are used for main gear and tail wheel (see offset 0370). Wrong land_pitch values cause very strange/funny effects of jumping planes. It also influences the plane's ability to take off. Your aircraft may not take off if the angle of pitch is too high. Please reduce it in this case, even if this is not realistic.

fm_control_data gear;
{

float max; max position
float min;
min position
float rate; rate of change
}


byte offset

fm_gear_data aGears[3];
{

0370 float n; don't know it's meaning, keep it as it is

fm_vector3 position;
{0374 float x;
0378 float y;
037C float z;
}

}

Starting at byte 0374 you have three groups of 3 coodinates (x, y, z) each. These are the positions of the 2 main landing gear parts and the tail wheel. Just get the coordinates with '3dz! Studio' and convert them to feet. Pay attention: It can happen that your plane explodes on the ground because you changed (reduced) the landing gear height. This happens because any of the hitbubbles or the damage positions starting at byte offset 03A0 now hits the ground. Please correct them first.

damage size

03A0 fm_vector3 damage_pos[7];
{


float x;
float y;
float z;
}

These are 7 damage positions used for crashes or belly landings: front_belly, mid_belly, tail_low, wingtip_left, wingtip_right, front_top, tail_top. The seven positions create something like an outline for the plane that is used to calculate crashes with groundobjects.
Use the lower wingtip coordinates for biplanes.
BTW: You will have very nice and realistic looking belly landings when these values are set properly. Also will it improove AI crash landings.

Chris Coons told me:
The damage_pos array is only used when landing without landing gear (or landing rough)... it seems to only be checked to determine drag along the ground and damage as the aircraft slides. Probably it was intended to be a more realistic damage model in the air (such as increased drag when one wing is shot), but we ran out of time so never got to put it in all the way.

fm_vector3 wing_pos[2];
{

03F4 float x;
float y;
float z;
}

Don't know it's meaning, maybe it controls the position where the torn off wings appear.

engine positions (smoke)

fm_vector3 engine_pos[4];
{

040C float x;
float y;
float z;
}

Controls the position of the engine smoke.

hit locations

fm_hit_data aHitLocation[8];
{fm_vector3 position;
{043C float x;
float y;
float z;
}


float radius2;

These are the positions and sizes of the hitbubbles. You can use Aircraft Edit to change them. The locations are: front (engine for single engined planes), pilot, mid (fuselage), tail, inner_wing_left (left engine for twin engined planes), outer_wing_left, inner_wing_right (right engine), outer_wing_left.
Pay attention with multi engined planes. While the wings contain only the mecanical parts for single engined planes they are also used for the engines on 2- or 4- engined planes. That's why you have to add the hitpoints of the engine to the hitpoints of the wings for multi engined aircraft. Maybe the outer wings are used for the outer engines on 4-engined planes.
The positions of the hitbubbles can easily estimated with '3dz! Studio' but should be extensively tested in game. Test every Hitbubble for itself setting the radius of all other hitbubbles to zero. Now change the plane you want to test to bomber and fly a mission, now 'attack' your comrades watching the hits at close distance and do corrections to the size and positions of the hitbubbles if necessary. You can also start a mission on the ground and slowly drive around your comrades shooting at them to test the position of the hitbubbles from different directions...
Radius2 means the radius squared of the hitbubble. Best you take the values from Knegels RP models.
The hitpoints themselves are stored in planes.dat and can easily be changed with Aircraft Edit.

}
long BigRadius;
float radius2;

Chris Coons told me:
The value BigRadius is the radius of the bounding cube around the aircraft that the bullets are first checked against. If the bullet is within the cube, then it is checked against each hit location. Each hit location is a sphere with the same radius, which is the value in Radius2 (radius squared).
BigRadius is also used for determining plane-plane collision.
So ideally BigRadius would cover the entire aircraft, and the hit locations would be evenly spread out so the sum of the radius2 covered the entire body. But you could alter those to make a bullet that really "hit" the aircraft go through two different hit locations and it would become a "miss," for example.

engine damage points
float EngineRating;//

weapons hardpoints
fm_vector3 aHardPoints[5];
{

float x;
float y;
float z;
}

These are the positions where the bombs appear when they are dropped. The positions should be the same as the 3dz-hardpoints positions.

}

Ok, that's it. Please excuse my English, these notes have been taken very quickly. :o)
If you have questions just email me or ask at SimHQ.
Andy (andy@wiesel-network.de)

_

Some more notes I copied from SimHQ:

Undercarriage Height Settings

Now, in order to achieve deck landings on a 3dz that does not actually support anything, I have been making the “virtual” undercarriage in the .FLT files for each aircraft VERY tall. You see, the values for undercarriage height in the .FLT files are expressed in feet. It is as simple as that (something had to be simple). You set the “land height” float value at offset # 35C to your desired height and the mission will commence with all squad members at that height. The HUD displays 0 ft which is why I think it is a “land” height. As soon as the player starts his engine, the correct altitude is displayed and he drops from this height. The AI squad members remain at that “land” height until the player takes them over. This 35C figure can be set to any height, 1000, 10 000, 30 000 ft.
The undercarriage maximum heights for each strut at offset # 37C, 38C and 39C are limited to 100 ft in height. Once you start your engine, your aircraft comes to rest at the z coordinate maximums for each gear strut. (This probably explains why some aircraft have exploded on engine start in the past). So if you set 35C at a compatible height (less than 100ft) your aircraft comes to rest on the z heights with no visible change to the player. This takes a lot of trial and error to achieve (because I can’t work out the mathematical or structural relationship between the 35c value and the z coordinates and it changes as you increase height).