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Advanced Ballistics - Drag model revamp & Spin drift correction #5566

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merged 16 commits into from
Oct 6, 2017
Merged

Advanced Ballistics - Drag model revamp & Spin drift correction #5566

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6763b07
Advanced Ballistics - Drag model revamp
ulteq Sep 27, 2017
7b2cc57
The Mach number is now calculated in relation to the air temperature.
ulteq Sep 28, 2017
e8f5532
Improved speed of sound calculation accuracy.
ulteq Sep 28, 2017
f338faf
Advanced Ballistics - DLL update
ulteq Sep 28, 2017
681e50e
Advanced Ballistics - Added drag function reference (JBM Ballistics)
ulteq Sep 28, 2017
79ab583
Advanced Ballistics - Fixed calculation error in the spin drift simul…
ulteq Sep 29, 2017
0c62f09
More descriptive variable names
ulteq Sep 30, 2017
b307f5f
Minor performance optimizations
ulteq Oct 1, 2017
2779a4e
Fixed some minor issues
ulteq Oct 1, 2017
12c1967
DLL rebuild
ulteq Oct 1, 2017
333f2d0
Utilize new 'toFixed' script command
ulteq Oct 3, 2017
6e1189c
Fixed a typo
ulteq Oct 3, 2017
8b8d4a3
Use correct reference speed for the drag compensation
ulteq Oct 3, 2017
82f5552
Updated all 'airFriction' values to match the new drag model
ulteq Oct 3, 2017
ba52cd3
'Default' atmosphere now equals the ICAO standard atmosphere
ulteq Oct 3, 2017
15e33b2
Update reference humidity to meet the ICAO standard
ulteq Oct 3, 2017
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3 changes: 2 additions & 1 deletion addons/atragmx/functions/fnc_calculate_distance_at_velocity.sqf
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,8 @@ private _distance = 0;
while {_velocity > _thresholdVelocity} do {
private _bc = GVAR(targetSolutionInput) select 14;
private _dragModel = GVAR(targetSolutionInput) select 15;
private _drag = parseNumber(("ace_advanced_ballistics" callExtension format["retard:%1:%2:%3", _dragModel, _bc, _velocity]));
private _temperature = GVAR(targetSolutionInput) select 5;
private _drag = parseNumber(("ace_advanced_ballistics" callExtension format["retard:%1:%2:%3:%4", _dragModel, _bc, _velocity, _temperature]));
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Whitespace after parseNumber and format.

_distance = _distance + _velocity * __DELTA_T;
_velocity = _velocity - (_drag * __DELTA_T);
};
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2 changes: 1 addition & 1 deletion addons/atragmx/functions/fnc_calculate_solution.sqf
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Expand Up @@ -118,7 +118,7 @@ while {_TOF < 15 && (_bulletPos select 1) < _targetRange} do {
_trueSpeed = vectorMagnitude _trueVelocity;

if (missionNamespace getVariable [QEGVAR(advanced_ballistics,enabled), false]) then {
private _drag = parseNumber(("ace_advanced_ballistics" callExtension format["retard:%1:%2:%3", _dragModel, _bc, _trueSpeed]));
private _drag = parseNumber(("ace_advanced_ballistics" callExtension format["retard:%1:%2:%3:%4", _dragModel, _bc, _trueSpeed, _temperature]));
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Same.

_bulletAccel = (vectorNormalized _trueVelocity) vectorMultiply (-1 * _drag);
} else {
_bulletAccel = _trueVelocity vectorMultiply (_trueSpeed * _airFriction);
Expand Down
2 changes: 1 addition & 1 deletion addons/rangecard/functions/fnc_calculateRangeCard.sqf
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Original file line number Diff line number Diff line change
Expand Up @@ -103,7 +103,7 @@ while {_TOF < 6 && (_bulletPos select 1) < _targetRange} do {
_trueSpeed = vectorMagnitude _trueVelocity;

if (_useABConfig) then {
private _drag = parseNumber(("ace_advanced_ballistics" callExtension format["retard:%1:%2:%3", _dragModel, _bc, _trueSpeed]));
private _drag = parseNumber(("ace_advanced_ballistics" callExtension format["retard:%1:%2:%3:%4", _dragModel, _bc, _trueSpeed, _temperature]));
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Same.

_bulletAccel = (vectorNormalized _trueVelocity) vectorMultiply (-1 * _drag);
} else {
_bulletAccel = _trueVelocity vectorMultiply (_trueSpeed * _airFriction * _airFrictionCoef);
Expand Down
120 changes: 31 additions & 89 deletions extensions/advanced_ballistics/AdvancedBallistics.cpp
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Expand Up @@ -21,6 +21,8 @@
#define SPECIFIC_GAS_CONSTANT_DRY_AIR 287.058f
#define STD_AIR_DENSITY_ICAO 1.22498f
#define STD_AIR_DENSITY_ASM 1.20885f
#define BC_CONVERSION_FACTOR 0.00068418f
#define SPEED_OF_SOUND(t) (331.3 + std::sqrt(1 + t / 273.15f))

struct Bullet {
double airFriction;
Expand Down Expand Up @@ -114,117 +116,55 @@ double calculateAtmosphericCorrection(double ballisticCoefficient, double temper
}
}

double calculateRetard(int DragFunction, double DragCoefficient, double Velocity) {
double vel = Velocity * 3.2808399;
double val = -1;
double A = -1;
double M = -1;
double calculateRetard(int DragFunction, double DragCoefficient, double Velocity, double Mach) {
std::vector<double> machNumbers = {};
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Performance optimization would be to have these tables be built at compile-time.
Or making them global variables and just selecting a pointer to them here.
Because this way you have a memory allocation and memcpy everytime a drag function is choosen.

std::vector<double> dragCoefficients = {};
double m = Velocity / Mach;

switch (DragFunction) {
case 1:
if (vel> 4230) { A = 1.477404177730177e-04; M = 1.9565; }
else if (vel> 3680) { A = 1.920339268755614e-04; M = 1.925; }
else if (vel> 3450) { A = 2.894751026819746e-04; M = 1.875; }
else if (vel> 3295) { A = 4.349905111115636e-04; M = 1.825; }
else if (vel> 3130) { A = 6.520421871892662e-04; M = 1.775; }
else if (vel> 2960) { A = 9.748073694078696e-04; M = 1.725; }
else if (vel> 2830) { A = 1.453721560187286e-03; M = 1.675; }
else if (vel> 2680) { A = 2.162887202930376e-03; M = 1.625; }
else if (vel> 2460) { A = 3.209559783129881e-03; M = 1.575; }
else if (vel> 2225) { A = 3.904368218691249e-03; M = 1.55; }
else if (vel> 2015) { A = 3.222942271262336e-03; M = 1.575; }
else if (vel> 1890) { A = 2.203329542297809e-03; M = 1.625; }
else if (vel> 1810) { A = 1.511001028891904e-03; M = 1.675; }
else if (vel> 1730) { A = 8.609957592468259e-04; M = 1.75; }
else if (vel> 1595) { A = 4.086146797305117e-04; M = 1.85; }
else if (vel> 1520) { A = 1.954473210037398e-04; M = 1.95; }
else if (vel> 1420) { A = 5.431896266462351e-05; M = 2.125; }
else if (vel> 1360) { A = 8.847742581674416e-06; M = 2.375; }
else if (vel> 1315) { A = 1.456922328720298e-06; M = 2.625; }
else if (vel> 1280) { A = 2.419485191895565e-07; M = 2.875; }
else if (vel> 1220) { A = 1.657956321067612e-08; M = 3.25; }
else if (vel> 1185) { A = 4.745469537157371e-10; M = 3.75; }
else if (vel> 1150) { A = 1.379746590025088e-11; M = 4.25; }
else if (vel> 1100) { A = 4.070157961147882e-13; M = 4.75; }
else if (vel> 1060) { A = 2.938236954847331e-14; M = 5.125; }
else if (vel> 1025) { A = 1.228597370774746e-14; M = 5.25; }
else if (vel> 980) { A = 2.916938264100495e-14; M = 5.125; }
else if (vel> 945) { A = 3.855099424807451e-13; M = 4.75; }
else if (vel> 905) { A = 1.185097045689854e-11; M = 4.25; }
else if (vel> 860) { A = 3.566129470974951e-10; M = 3.75; }
else if (vel> 810) { A = 1.045513263966272e-08; M = 3.25; }
else if (vel> 780) { A = 1.291159200846216e-07; M = 2.875; }
else if (vel> 750) { A = 6.824429329105383e-07; M = 2.625; }
else if (vel> 700) { A = 3.569169672385163e-06; M = 2.375; }
else if (vel> 640) { A = 1.839015095899579e-05; M = 2.125; }
else if (vel> 600) { A = 5.71117468873424e-05; M = 1.950; }
else if (vel> 550) { A = 9.226557091973427e-05; M = 1.875; }
else if (vel> 250) { A = 9.337991957131389e-05; M = 1.875; }
else if (vel> 100) { A = 7.225247327590413e-05; M = 1.925; }
else if (vel> 65) { A = 5.792684957074546e-05; M = 1.975; }
else if (vel> 0) { A = 5.206214107320588e-05; M = 2.000; }
dragCoefficients = { 0.2629, 0.2558, 0.2487, 0.2413, 0.2344, 0.2278, 0.2214, 0.2155, 0.2104, 0.2061, 0.2032, 0.2020, 0.2034, 0.2165, 0.2230, 0.2313, 0.2417, 0.2546, 0.2706, 0.2901, 0.3136, 0.3415, 0.3734, 0.4084, 0.4448, 0.4805, 0.5136, 0.5427, 0.5677, 0.5883, 0.6053, 0.6191, 0.6393, 0.6518, 0.6589, 0.6621, 0.6625, 0.6607, 0.6573, 0.6528, 0.6474, 0.6413, 0.6347, 0.6280, 0.6210, 0.6141, 0.6072, 0.6003, 0.5934, 0.5867, 0.5804, 0.5743, 0.5685, 0.5630, 0.5577, 0.5527, 0.5481, 0.5438, 0.5397, 0.5325, 0.5264, 0.5211, 0.5168, 0.5133, 0.5105, 0.5084, 0.5067, 0.5054, 0.5040, 0.5030, 0.5022, 0.5016, 0.5010, 0.5006, 0.4998, 0.4995, 0.4992, 0.4990, 0.4988 };
machNumbers = { 0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.70, 0.725, 0.75, 0.775, 0.80, 0.825, 0.85, 0.875, 0.90, 0.925, 0.95, 0.975, 1.0, 1.025, 1.05, 1.075, 1.10, 1.125, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, 2.00, 2.05, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40, 2.45, 2.50, 2.60, 2.70, 2.80, 2.90, 3.00, 3.10, 3.20, 3.30, 3.40, 3.50, 3.60, 3.70, 3.80, 3.90, 4.00, 4.20, 4.40, 4.60, 4.80, 5.00 };
break;

case 2:
if (vel> 1674) { A = .0079470052136733; M = 1.36999902851493; }
else if (vel> 1172) { A = 1.00419763721974e-03; M = 1.65392237010294; }
else if (vel> 1060) { A = 7.15571228255369e-23; M = 7.91913562392361; }
else if (vel> 949) { A = 1.39589807205091e-10; M = 3.81439537623717; }
else if (vel> 670) { A = 2.34364342818625e-04; M = 1.71869536324748; }
else if (vel> 335) { A = 1.77962438921838e-04; M = 1.76877550388679; }
else if (vel> 0) { A = 5.18033561289704e-05; M = 1.98160270524632; }
dragCoefficients = { 0.2303, 0.2298, 0.2287, 0.2271, 0.2251, 0.2227, 0.2196, 0.2156, 0.2107, 0.2048, 0.1980, 0.1905, 0.1828, 0.1758, 0.1702, 0.1669, 0.1664, 0.1667, 0.1682, 0.1711, 0.1761, 0.1831, 0.2004, 0.2589, 0.3492, 0.3983, 0.4075, 0.4103, 0.4114, 0.4106, 0.4089, 0.4068, 0.4046, 0.4021, 0.3966, 0.3904, 0.3835, 0.3759, 0.3678, 0.3594, 0.3512, 0.3432, 0.3356, 0.3282, 0.3213, 0.3149, 0.3089, 0.3033, 0.2982, 0.2933, 0.2889, 0.2846, 0.2806, 0.2768, 0.2731, 0.2696, 0.2663, 0.2632, 0.2602, 0.2572, 0.2543, 0.2515, 0.2487, 0.2460, 0.2433, 0.2408, 0.2382, 0.2357, 0.2333, 0.2309, 0.2262, 0.2217, 0.2173, 0.2132, 0.2091, 0.2052, 0.2014, 0.1978, 0.1944, 0.1912, 0.1851, 0.1794, 0.1741, 0.1693, 0.1648 };
machNumbers = { 0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.775, 0.80, 0.825, 0.85, 0.875, 0.90, 0.925, 0.95, 0.975, 1.0, 1.025, 1.05, 1.075, 1.10, 1.125, 1.15, 1.175, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, 2.00, 2.05, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40, 2.45, 2.50, 2.55, 2.60, 2.65, 2.70, 2.75, 2.80, 2.85, 2.90, 2.95, 3.00, 3.10, 3.20, 3.30, 3.40, 3.50, 3.60, 3.70, 3.80, 3.90, 4.00, 4.20, 4.40, 4.60, 4.80, 5.00 };
break;

case 5:
if (vel> 1730) { A = 7.24854775171929e-03; M = 1.41538574492812; }
else if (vel> 1228) { A = 3.50563361516117e-05; M = 2.13077307854948; }
else if (vel> 1116) { A = 1.84029481181151e-13; M = 4.81927320350395; }
else if (vel> 1004) { A = 1.34713064017409e-22; M = 7.8100555281422; }
else if (vel> 837) { A = 1.03965974081168e-07; M = 2.84204791809926; }
else if (vel> 335) { A = 1.09301593869823e-04; M = 1.81096361579504; }
else if (vel> 0) { A = 3.51963178524273e-05; M = 2.00477856801111; }
dragCoefficients = { 0.1710, 0.1719, 0.1727, 0.1732, 0.1734, 0.1730, 0.1718, 0.1696, 0.1668, 0.1637, 0.1603, 0.1566, 0.1529, 0.1497, 0.1473, 0.1463, 0.1489, 0.1583, 0.1672, 0.1815, 0.2051, 0.2413, 0.2884, 0.3379, 0.3785, 0.4032, 0.4147, 0.4201, 0.4278, 0.4338, 0.4373, 0.4392, 0.4403, 0.4406, 0.4401, 0.4386, 0.4362, 0.4328, 0.4286, 0.4237, 0.4182, 0.4121, 0.4057, 0.3991, 0.3926, 0.3861, 0.3800, 0.3741, 0.3684, 0.3630, 0.3578, 0.3529, 0.3481, 0.3435, 0.3391, 0.3349, 0.3269, 0.3194, 0.3125, 0.3060, 0.2999, 0.2942, 0.2889, 0.2838, 0.2790, 0.2745, 0.2703, 0.2662, 0.2624, 0.2588, 0.2553, 0.2488, 0.2429, 0.2376, 0.2326, 0.2280 };
machNumbers = { 0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.875, 0.90, 0.925, 0.95, 0.975, 1.0, 1.025, 1.05, 1.075, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, 2.00, 2.05, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40, 2.45, 2.50, 2.60, 2.70, 2.80, 2.90, 3.00, 3.10, 3.20, 3.30, 3.40, 3.50, 3.60, 3.70, 3.80, 3.90, 4.00, 4.20, 4.40, 4.60, 4.80, 5.00 };
break;

case 6:
if (vel> 3236) { A = 0.0455384883480781; M = 1.15997674041274; }
else if (vel> 2065) { A = 7.167261849653769e-02; M = 1.10704436538885; }
else if (vel> 1311) { A = 1.66676386084348e-03; M = 1.60085100195952; }
else if (vel> 1144) { A = 1.01482730119215e-07; M = 2.9569674731838; }
else if (vel> 1004) { A = 4.31542773103552e-18; M = 6.34106317069757; }
else if (vel> 670) { A = 2.04835650496866e-05; M = 2.11688446325998; }
else if (vel> 0) { A = 7.50912466084823e-05; M = 1.92031057847052; }
dragCoefficients = { 0.2617, 0.2553, 0.2491, 0.2432, 0.2376, 0.2324, 0.2278, 0.2238, 0.2205, 0.2177, 0.2155, 0.2138, 0.2126, 0.2121, 0.2122, 0.2132, 0.2154, 0.2194, 0.2229, 0.2297, 0.2449, 0.2732, 0.3141, 0.3597, 0.3994, 0.4261, 0.4402, 0.4465, 0.4490, 0.4497, 0.4494, 0.4482, 0.4464, 0.4441, 0.4390, 0.4336, 0.4279, 0.4221, 0.4162, 0.4102, 0.4042, 0.3981, 0.3919, 0.3855, 0.3788, 0.3721, 0.3652, 0.3583, 0.3515, 0.3447, 0.3381, 0.3314, 0.3249, 0.3185, 0.3122, 0.3060, 0.3000, 0.2941, 0.2883, 0.2772, 0.2668, 0.2574, 0.2487, 0.2407, 0.2333, 0.2265, 0.2202, 0.2144, 0.2089, 0.2039, 0.1991, 0.1947, 0.1905, 0.1866, 0.1794, 0.1730, 0.1673, 0.1621, 0.1574 };
machNumbers = { 0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.875, 0.90, 0.925, 0.95, 0.975, 1.0, 1.025, 1.05, 1.075, 1.10, 1.125, 1.15, 1.175, 1.20, 1.225, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, 2.00, 2.05, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40, 2.45, 2.50, 2.60, 2.70, 2.80, 2.90, 3.00, 3.10, 3.20, 3.30, 3.40, 3.50, 3.60, 3.70, 3.80, 3.90, 4.00, 4.20, 4.40, 4.60, 4.80, 5.00 };
break;

case 7:
if (vel> 4200) { A = 1.29081656775919e-09; M = 3.24121295355962; }
else if (vel> 3000) { A = 0.0171422231434847; M = 1.27907168025204; }
else if (vel> 1470) { A = 2.33355948302505e-03; M = 1.52693913274526; }
else if (vel> 1260) { A = 7.97592111627665e-04; M = 1.67688974440324; }
else if (vel> 1110) { A = 5.71086414289273e-12; M = 4.3212826264889; }
else if (vel> 960) { A = 3.02865108244904e-17; M = 5.99074203776707; }
else if (vel> 670) { A = 7.52285155782535e-06; M = 2.1738019851075; }
else if (vel> 540) { A = 1.31766281225189e-05; M = 2.08774690257991; }
else if (vel> 0) { A = 1.34504843776525e-05; M = 2.08702306738884; }
dragCoefficients = { 0.1198, 0.1197, 0.1196, 0.1194, 0.1193, 0.1194, 0.1194, 0.1194, 0.1193, 0.1193, 0.1194, 0.1193, 0.1194, 0.1197, 0.1202, 0.1207, 0.1215, 0.1226, 0.1242, 0.1266, 0.1306, 0.1368, 0.1464, 0.1660, 0.2054, 0.2993, 0.3803, 0.4015, 0.4043, 0.4034, 0.4014, 0.3987, 0.3955, 0.3884, 0.3810, 0.3732, 0.3657, 0.3580, 0.3440, 0.3376, 0.3315, 0.3260, 0.3209, 0.3160, 0.3117, 0.3078, 0.3042, 0.3010, 0.2980, 0.2951, 0.2922, 0.2892, 0.2864, 0.2835, 0.2807, 0.2779, 0.2752, 0.2725, 0.2697, 0.2670, 0.2643, 0.2615, 0.2588, 0.2561, 0.2533, 0.2506, 0.2479, 0.2451, 0.2424, 0.2368, 0.2313, 0.2258, 0.2205, 0.2154, 0.2106, 0.2060, 0.2017, 0.1975, 0.1935, 0.1861, 0.1793, 0.1730, 0.1672, 0.1618 };
machNumbers = { 0.0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.725, 0.75, 0.775, 0.80, 0.825, 0.85, 0.875, 0.90, 0.925, 0.95, 0.975, 1.0, 1.025, 1.05, 1.075, 1.10, 1.125, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, 2.00, 2.05, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40, 2.45, 2.50, 2.55, 2.60, 2.65, 2.70, 2.75, 2.80, 2.85, 2.90, 2.95, 3.00, 3.10, 3.20, 3.30, 3.40, 3.50, 3.60, 3.70, 3.80, 3.90, 4.00, 4.20, 4.40, 4.60, 4.80, 5.00 };
break;

case 8:
if (vel> 3571) { A = .0112263766252305; M = 1.33207346655961; }
else if (vel> 1841) { A = .0167252613732636; M = 1.28662041261785; }
else if (vel> 1120) { A = 2.20172456619625e-03; M = 1.55636358091189; }
else if (vel> 1088) { A = 2.0538037167098e-16; M = 5.80410776994789; }
else if (vel> 976) { A = 5.92182174254121e-12; M = 4.29275576134191; }
else if (vel> 0) { A = 4.3917343795117e-05; M = 1.99978116283334; }
dragCoefficients = { 0.2105, 0.2105, 0.2104, 0.2104, 0.2103, 0.2103, 0.2103, 0.2103, 0.2103, 0.2102, 0.2102, 0.2102, 0.2102, 0.2102, 0.2103, 0.2103, 0.2104, 0.2104, 0.2105, 0.2106, 0.2109, 0.2183, 0.2571, 0.3358, 0.4068, 0.4378, 0.4476, 0.4493, 0.4477, 0.4450, 0.4419, 0.4353, 0.4283, 0.4208, 0.4133, 0.4059, 0.3986, 0.3915, 0.3845, 0.3777, 0.3710, 0.3645, 0.3581, 0.3519, 0.3458, 0.3400, 0.3343, 0.3288, 0.3234, 0.3182, 0.3131, 0.3081, 0.3032, 0.2983, 0.2937, 0.2891, 0.2845, 0.2802, 0.2720, 0.2642, 0.2569, 0.2499, 0.2432, 0.2368, 0.2308, 0.2251, 0.2197, 0.2147, 0.2101, 0.2058, 0.2019, 0.1983, 0.1950, 0.1890, 0.1837, 0.1791, 0.1750, 0.1713 };
machNumbers = { 0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.825, 0.85, 0.875, 0.90, 0.925, 0.95, 0.975, 1.0, 1.025, 1.05, 1.075, 1.10, 1.125, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, 2.00, 2.05, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40, 2.45, 2.50, 2.60, 2.70, 2.80, 2.90, 3.00, 3.10, 3.20, 3.30, 3.40, 3.50, 3.60, 3.70, 3.80, 3.90, 4.00, 4.20, 4.40, 4.60, 4.80, 5.00 };
break;

default:
break;

}

if (A != -1 && M != -1 && vel > 0 && vel < 10000) {
val = A * pow(vel, M) / DragCoefficient;
val = val / 3.2808399;
return val;
for (int i = 0; i < machNumbers.size(); i++) {
if (machNumbers[i] >= m) {
int previousIdx = std::max(0, i - 1);
double lcd = dragCoefficients[previousIdx];
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longer variable names would be neat here. I have no idea what lcd/lmn/cd mean.

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Agreed. Even though all we do here is a linear interpolation between the data points.

double lmn = machNumbers[previousIdx];
double cd = lcd + (dragCoefficients[i] - lcd) * (m - lmn) / (machNumbers[i] - lmn);
return BC_CONVERSION_FACTOR * (cd / DragCoefficient) * std::pow(Velocity, 2);
}
}

return 0.0;
Expand Down Expand Up @@ -309,7 +249,7 @@ double calculateZeroAngle(double zeroRange, double muzzleVelocity, double boreHe

v = std::sqrt(vx*vx + vy*vy);

double retard = calculateRetard(dragModel, ballisticCoefficient, v);
double retard = calculateRetard(dragModel, ballisticCoefficient, v, SPEED_OF_SOUND(15));
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You are calculating this constant.. at runtime. Everytime the function is called. Why?

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RELEVANT VARIABLE NAME

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@ulteq ulteq Sep 30, 2017 •
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@dedmen, I expect it to be optimized away by the compiler.

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It won't be here. because std::sqrt is not constexpr.

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@ulteq ulteq Sep 30, 2017 •
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GCC 7.2.0 is smart enough. I will test VS 2017 tomorrow.

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@ulteq ulteq Oct 1, 2017 •
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Visual Studio 2017 produces the exact same assembly code in both cases:

#define SPEED_OF_SOUND(t) (331.3 + std::sqrt(1 + t / 273.15f))
...
double r = calcR(dragModel, ballisticCoefficient, v, SPEED_OF_SOUND(15));

#define SPEED_OF_SOUND(t) (331.3 + std::sqrt(1 + t / 273.15f))
...
const float c = SPEED_OF_SOUND(15);
double r = calcR(dragModel, ballisticCoefficient, v, c);

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moving it into a const float doesn't change that std::sqrt is not constexpr before C++17.
Actually.. Not even C++17 has constexpr sqrt.
Does that assembly code that it produces calculate the Speed of sound. Or does it use a constant? If it calculates then it does exactly what I said

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Just did a release compile. And yes it is calling sqrt at runtime.

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@ulteq ulteq Oct 1, 2017 •
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I will just replace it with 340.275.

double ax = vx / v * -retard;
double ay = vy / v * -retard;
ax += gx;
Expand Down Expand Up @@ -366,13 +306,15 @@ void __stdcall RVExtension(char *output, int outputSize, const char *function)
double ballisticCoefficient = 1.0;
int dragModel = 1;
double velocity = 0.0;
double temperature = 15.0;
double retard = 0.0;

dragModel = strtol(strtok_s(NULL, ":", &next_token), NULL, 10);
ballisticCoefficient = strtod(strtok_s(NULL, ":", &next_token), NULL);
velocity = strtod(strtok_s(NULL, ":", &next_token), NULL);
temperature = strtod(strtok_s(NULL, ":", &next_token), NULL);

retard = calculateRetard(dragModel, ballisticCoefficient, velocity);
retard = calculateRetard(dragModel, ballisticCoefficient, velocity, SPEED_OF_SOUND(temperature));
// int n = sprintf(output, "%f", retard);

outputStr << retard;
Expand Down Expand Up @@ -652,7 +594,7 @@ void __stdcall RVExtension(char *output, int outputSize, const char *function)

ballisticCoefficient = calculateAtmosphericCorrection(ballisticCoefficient, temperature, pressure, bulletDatabase[index].humidity, bulletDatabase[index].atmosphereModel);
ballisticCoefficient *= bulletDatabase[index].bcDegradation;
drag = deltaT * calculateRetard(bulletDatabase[index].dragModel, ballisticCoefficient, trueSpeed);
drag = deltaT * calculateRetard(bulletDatabase[index].dragModel, ballisticCoefficient, trueSpeed, SPEED_OF_SOUND(temperature));
accel[0] = (trueVelocity[0] / trueSpeed) * drag;
accel[1] = (trueVelocity[1] / trueSpeed) * drag;
accel[2] = (trueVelocity[2] / trueSpeed) * drag;
Expand Down