native Float:MPDistanceCameraToLocation(Float:CamX, Float:CamY, Float:CamZ, Float:ObjX, Float:ObjY, Float:ObjZ, Float:FrX, Float:FrY, Float:FrZ); // calculates how distant target aim is from camera data pointed towards a certain point

Float: DistanceCameraTargetToLocation(Float:CamX, Float:CamY, Float:CamZ, Float:ObjX, Float:ObjY, Float:ObjZ,  Float:FrX, Float:FrY, Float:FrZ)

stock IsPlayerAimingAt(playerid, Float:x, Float:y, Float:z, Float:radius)
{
    new Float:cx,Float:cy,Float:cz,Float:fx,Float:fy,Float:fz;
    GetPlayerCameraPos(playerid, cx, cy, cz);
    GetPlayerCameraFrontVector(playerid, fx, fy, fz);
    return (radius >= MPDistanceCameraToLocation(cx, cy, cz, x, y, z, fx, fy, fz));
}

native Float:MPGetVehicleUpsideDown(vehicleid); // returns values such as 1.0 as pointing up, -1.0 is totally upside down. returns -5.0 if car id is not 1..2000.

//1.0 = car placed on level ground / pointing up
//0.0 = car is 90 degrees on side
//-1.0 would be totally upside down
//-5.0 if car id is not 1..2000.

public OnPlayerUpdate(playerid)
{
    new vehicleid = GetPlayerVehicleID(playerid);
    if(vehicleid != 0)
    {
        new Float:health;
        GetVehicleHealth(vehicleid, health);
        newVehicleHealth[vehicleid] = health;
        if(newVehicleHealth[vehicleid] != oldVehicleHealth[vehicleid])
        {
            CallLocalFunction("OnPlayerVehicleHealthChange", "iiff", playerid, vehicleid, newVehicleHealth[vehicleid], oldVehicleHealth[vehicleid]);
            oldVehicleHealth[vehicleid] = newVehicleHealth[vehicleid];
        }
    }
} 

forward OnPlayerVehicleHealthChange(playerid, vehicleid, Float:newhealth, Float:oldhealth);
public OnPlayerVehicleHealthChange(playerid, vehicleid, Float:newhealth, Float:oldhealth)
{
    #pragma unused playerid
    #pragma unused newhealth
    #pragma unused oldhealth
    if(-1.5 <= MPGetVehicleUpsideDown(vehicleid) <= -0.5)
    {
        new Float:Angle, Float:x, Float:y, Float:z;
        GetVehicleVelocity(vehicleid, x, y, z);
        GetVehicleZAngle(vehicleid, Angle);
        SetVehicleZAngle(vehicleid, Angle);
        SetVehicleVelocity(vehicleid, x, y, z);
    }
    return 1;
}

native MPGetAimTarget(PlayerID, Float:SeekRadius = 50.0); // returns player that this player is aiming at or invalid player id if no player in target area.

public OnPlayerUpdate(playerid)
{
    new aimingtarget = MPGetAimTarget(playerid, 50.0);
    if(aimingtarget != INVALID_PLAYER_ID)
    {
        SendClientMessage(playerid, "You are aiming at a player.");
    }
    return 1;
}

native MPGetTrailerTowingVehicle(vehicleid); // finds the vehicle that this trailer is attached to, returns invalid_vehicle_id if invalid or not attached to any towing vehicle.

new vehicleid = CreateVehicle(402, 0.0, 0.0, 0.0, 180.0, -1, -1, -1);
new vehicletrailer = CreateVehicle(402, 0.0, 0.0, 0.0, 180.0, -1, -1, -1);

AttachTrailerToVehicle(vehicletrailer, vehicleid);

new trailerowner = MPGetTrailerTowingVehicle(vehicletrailer);

printf("trailerowner = %d - vehicleid = %d", trailerowner, vehicleid);

native MPGetVehicleDriver(vehicleid);

public OnPlayerStateChange(playerid, newstate, oldstate);
{
    switch(newstate)
    {
        case PLAYER_STATE_PASSENGER:
        {
            new vehicleid = GetPlayerVehicleID(playerid),
                mydriver = MPGetVehicleDriver(vehicleid),
                str[64]
            ;
            format(str, 64, "Driver of this vehicle is %d", mydriver);
            SendClientMessage(playerid, -1, str);
        }
    }
    return 1;
}

native MPGetVehicleDriverCount(vehicleid); // returns number of drivers a car has (important to solve 2 drivers 1 car issue - if you wrote any decent anticheat you know what i mean)

public OnPlayerUpdate(playerid)
{
    new vehicleid = GetPlayerVehicleID(playerid);
    if(1 <= vehicleid <= 2000 )
    {
        new drivercount = MPGetVehicleDriverCount(vehicleid);
        if(drivercount > 1)
        {
            for(new i = 0; i < MAX_PLAYERS; i++)
            {
                if(GetPlayerVehicleID(i) != vehicleid) continue;
                RemovePlayerFromVehicle(i);
            }
        }
    }
    return 1;
}

native MPGetVehicleOccupantCnt(vehicleid); // returns number of player a vehicle is carrying

public OnPlayerStateChange(playerid, newstate, oldstate);
{
    switch(newstate)
    {
        case PLAYER_STATE_PASSENGER:
        {
            new vehicleid = GetPlayerVehicleID(playerid),
                passengercount = MPGetVehicleOccupantCnt(vehicleid),
                str[64]
            ;
            format(str, 64, "There are %d players in this vehicle", passengercount);
            SendClientMessage(playerid, -1, str);
        }
    }
    return 1;
}

native MPGetVehicleSurfersCnt(vehicleid); // returns number of players surfing a vehicle

public OnPlayerStateChange(playerid, newstate, oldstate);
{
    switch(newstate)
    {
        case PLAYER_STATE_PASSENGER:
        {
            new vehicleid = GetPlayerVehicleID(playerid),
                surfingcount+ = MPGetVehicleSurfersCnt(vehicleid),
                str[64]
            ;
            format(str, 64, "There are %d players surfing this vehicle", surfingcount);
            SendClientMessage(playerid, -1, str);
        }
    }
    return 1;
}

native Float:MPClamp360(Float:value);

<&JernejL> it's useful if you use stuff like
<&JernejL> difference between 2 angles
<&JernejL> to make a "x'o clock" system
<&JernejL> then you need proper angles clamped to that range

public OnGameModeInit()
{
    printf("%0.2f", MPClamp360(361.0));
    return 1;
}

native Float:MPDistance(Float:v1x, Float:v1y, Float:v1z, Float:v2x, Float:v2y, Float:v2z);  // distance between 2 points

#define GetDistanceBetweenPoints MPDistance

native Float:MPFDistance(Float:v1x, Float:v1y, Float:v1z, Float:v2x, Float:v2y, Float:v2z); // distance between 2 points (faster but less precise)

native Float:MPFSQRT(Float:value);  // Faster sqrt (****** the 0x5f3759df method)