Descent 3 (Outrage's source release, DescentDevelopers/Descent3 at the initial import)

The README of the Descent 3 source release, at its initial import, calls it "the latest version of the Descent 3 source code" and says it "includes the '1.5' patch that Jeff Slutter and Kevin Bentley wrote several years ago"; the SourceSafe header comment of WeaponFire.cpp gives its last revision as 279, dated 9/20/01. descent3/source-version

Value: 1.5

The game shipped in 1999, so the released code is later than the retail build. The headers of other cited files are dated from March 2000 (object.cpp) to September 2001 (player.h); physics/physics.cpp has none. The 1.5 patch was never released as a patch.

Cited by: Descent 3

In Descent 3's released source, which includes the unreleased "1.5" patch, the player ship's thrust is the sum of a forward, an up, and a sideways push along the ship's own axes, each the control's value times full_thrust, the whole scaled by the player's movement_scalar and by 1.3 outdoors; the physics then moves a thrusting object against a drag proportional to velocity, solved in closed form over the frame: v = (v₀ − F/d)·e^(−(d/m)·t) + F/d. Computed from that formula, drag acts while the ship thrusts too, and speed levels off at F/d, as in Doom, whose floor friction multiplies momentum by 0.90625 each tic thrust or not; Quake's ground acceleration instead stops at the wish speed. descent3/ship-thrust

About: Descent 3 Inertia

{
 "settled_speed": "full_thrust / drag",
 "outdoor_scale": 1.3
}

The ship's mass, drag, and full_thrust are in the game's data tables, not the source, so the settled speed in units per second isn't known here. Doom's friction applies only on the floor (doom/friction). The code is the release's, not the 1999 retail build's.

Cited by: Descent 3, Six degrees of freedom

Descent 3's released source turns the player ship on three axes the same way it moves it on three: pitch, heading, and bank each take the control's value times full_rotthrust times the player's turn_scalar, and an object flagged PF_USES_THRUST with a rotational drag above 0 has its turning speed solved against that drag with the same closed form, ω = (ω₀ − R/d)·e^(−(d/m)·t) + R/d. Computed from it, a held turn levels off at R/d and a released one fades out at rate d/m. The input code clamps pitch to 0.75 and heading and bank to 1, except in a Macintosh build, which skips those three clamps; before the drag step, PhysicsDoSimRot can add auto-leveling thrust to pitch and bank, which this claim doesn't cover. descent3/ship-rotation

About: Descent 3 Six degrees of freedom

{
 "pitch_limit": 0.75,
 "heading_limit": 1,
 "bank_limit": 1
}

The comments in both force functions call the drag "linear air drag". Auto-leveling (bank, and a pitch leveling for new pilots) runs earlier in PhysicsDoSimRot under several settings and is left for a later claim.

Cited by: Descent 3, Six degrees of freedom

Descent 3's input code clamps the forward, up, and sideways thrust controls to ±1 each, separately, and the released source adds the three pushes along the ship's perpendicular axes, so all three held at once push √3 ≈ 1.73 times as hard as forward alone, and, computed from the linear drag, the ship settles at 1.73 times the speed; Doom does the same with two axes, clamping its forward and side moves apart and thrusting them at 90°. descent3/summed-axes

About: Descent 3 Strafe-running

Value: 1.73 ×

The afterburner replaces the forward control with a larger value (descent-3/afterburner), so the ratio differs while it burns. Whether 1999's retail build summed the axes the same way is not checked.

Cited by: Descent 3, Strafe-running

Descent 3's released source gives the afterburner a 5-second tank (AFTERBURN_TIME, 5000 in an E3 demo build): while it is held and time is left, the forward control is replaced by the afterburner control times 1.6, and times a punch factor of 1.8 while over 90% of the tank is left, the factor easing to 1 by 80%, and the tank drains by the frame time. Let go, the tank refills by the frame time, or twice that with the "Afterburner" item in the inventory, but only while energy is above 5, and energy drops by the same amount, so a full refill costs 5 energy (computed) whichever rate applies. descent3/afterburner

About: Descent 3 Boost meter

{
 "tank_s": 5,
 "thrust": 1.6,
 "opening_punch": 1.8,
 "refill_energy": 5
}

The burn itself costs no energy; the refill does. The player starts with 100 energy and can hold up to 200 (INITIAL_ENERGY and MAX_ENERGY in player_external.h). A player whose controller flags lack PCBF_AFTERBURNER has the control zeroed first (object.cpp), which the atlas reads as a lock the game can set.

Cited by: Descent 3

In Descent 3's released source a homing weapon with thrust left starts homing 0.1 s after it is created, unless it is guided. Without a target, it scans every object in a room the missile's room can see: robots, players, and buildings with AI, not its own shooter, not cloaked, and only enemies of the shooter, inside a cone where the dot product of the direction to it with the missile's facing exceeds the weapon's homing_fov. In object order, a chaff chunk ends the scan (by a 1-in-4 roll in single player) and so does anything within 15 units (the distance between centers less both objects' sizes); otherwise the missile takes the object within 500 units most nearly straight ahead with a clear line to it. A target it has is kept while it stays inside the cone and either within 15 units, or within 500 units, in a visible room, with a clear line. descent3/homing-target

About: Descent 3 Homing missile

{
 "start_s": 0.1,
 "close_units": 15,
 "range_units": 500,
 "chaff_chance": 0.25
}

homing_fov is per weapon, from the data tables. In multiplayer the chaff pick is by object number (every fourth) instead of a roll. In the keep-a-target branch the tests for a ghost, a dead player, and a cloak read the missile (obj), not its target (WeaponFire.cpp lines 1489–1496), so they don't drop a target that cloaks after the lock; the head of the community tree still has them. Because WeaponDoFrame backdates last_track_time by 0.25 s before every homing step, the 0.20 s search interval is always past and a missile without a target searches every frame. When thrust_left runs out the missile stops thrusting and homing, and falls under gravity with drag 0.005.

Cited by: Descent 3, Homing missile

Descent 3's released source steers a homing weapon at the target's position plus a tenth of the target's velocity when the target moves under physics or walks. A weapon with rotational drag fires full full_rotthrust left or right and up or down, by which side of the missile the aim point is on, with no roll; one without it turns straight toward the aim point by at most full_rotthrust × the frame time and has its velocity set along its new facing at full_thrust/drag. A weapon whose shooter is not a player has its turning scaled by difficulty: 0.20, 0.70, 1.00, 1.20, and 1.40 from Trainee to Insane. descent3/homing-steer

About: Descent 3 Homing missile

{
 "lead_s": 0.1,
 "robot_turn_scale": [
  0.2,
  0.7,
  1,
  1.2,
  1.4
 ]
}

AITurnTowardsDir also skips any turn of less than one degree, and five degrees for objects larger than 32 units. For a weapon with rotational drag, the physics re-points its thrust along its new facing each frame (physics.cpp, "Updates the thrust vector to the orientation for homing weapons", in the code's comment). The turn rates themselves are per weapon, in the data tables.

Cited by: Descent 3, Homing missile

In Descent 3's released source, every 3 to 5 seconds an AI object that is more than barely aware and has its fourth goal slot free can take fright, by one of three tests on its own life_preservation (lp), the first two only for generic objects (robots, buildings, clutter, and powerups): its shields are under lp of its hit points, it dodged an enemy shot since the last check, it has fewer than 2 friends near, and a random number below lp; or it lost more than 25% × (1 − lp) of the shields it had some checks ago, and a random number below lp; or lp is over 0.5 and the friends it had are gone while enemies remain. Frightened, it wanders at its flee speed, facing the way it moves, for 10 × lp + 5 seconds. descent3/robot-fear

{
 "check_s": [
  3,
  5
 ],
 "duration": "10 × lp + 5 s"
}

The third test has no random roll. The routine's name, AIDoFreud, and its "Fear!!!!" debug line are the code's own; life_preservation, flee_vel_percent and hit points are per robot, in the data tables.

Cited by: Descent 3