Mirrored_Repos/veloren
1
0
Fork 0
mirror of https://gitlab.com/veloren/veloren.git synced 2024-08-30 18:12:32 +00:00
Code Issues Packages Projects Releases Wiki Activity

simplify the 0.1 scenario by using coth and acoth, not that coth is 1/tanh and acoth is atanh(1/x)

Browse Source
This commit is contained in:
Marcel Märtens 2022-07-25 22:44:20 +02:00
parent 3cd99b4711
commit 2d73375ff3
1 changed files with 14 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
common/systems/tests/phys/basic.rs
View File

@ -328,21 +328,25 @@ fn physics_theory() -> Result<(), Box<dyn Error>> {
let air_density = 1.225_f64;
let c = air_friction_co * air_friction_area * 0.5 * air_density * mass ;
let acc = 9.2_f64 * move_dir; // btw: cant accelerate faster than gravity on foot
const MAX_ACC: f64 = 9.2;
let acc = MAX_ACC * move_dir; // btw: cant accelerate faster than gravity on foot
let old_vel = vel;
// controller
// I know what you think, wtf, yep: https://math.stackexchange.com/questions/1929436/line-integral-of-force-of-air-resistanc
// basically an integral of the air resistance formula which scales with v^2 transformed with an ODE.
// The function besically takes its last result calculates the inverse* of it, adds the newly get speed to it and then run tanh again
// *inverse of the tanh and the factors before.
let past_fak = (c / (mass * acc.abs() ) ).sqrt() * old_vel;
// the original algorithm isn't able to keep a speed over the terminal velocity based on acc. however that is necessary, e.g. for pushbacks, falling, external factors and stopping (because of we stop acc would be 0 and the terminal vel would be 0 too)
// here we decide to reduce that factor by c each second.
let over_vel_keep = (past_fak * c.powf(dt)).max(1.0) * past_fak.signum(); //TODO signum needed
let vel = ( ((mass * acc.abs() ) / c ).sqrt() * over_vel_keep) * ( ( past_fak.clamp(-1.0, 1.0) ).atanh() + acc.signum() * (c * acc.abs() / mass).sqrt() * dt ).tanh();
//let vel = ((mass * acc.abs() + old_acc ) / c).sqrt() * ( ( ( (c / (mass * acc.abs() ) ).sqrt() * old_vel).clamp(-1.0, 1.0) ).atanh() + acc.signum() * (c * acc.abs() / mass).sqrt() * dt ).tanh();
// terminal velocity equals the maximum velocity that can be reached by acc alone
let vel_t = (mass * acc.abs() / c ).sqrt();
let _vel_tm = (mass * MAX_ACC / c ).sqrt();
// if our old_vel is bigger than vel_t we can use `coth(x) = 1/tanh(x)` and `acoth(x) = atanh(1/x)`
let revert_fak = old_vel / vel_t ;
let vel = if revert_fak.abs() >= 1.0 {
vel_t / ( ( 1.0 / revert_fak).atanh() + acc.signum() * (c * acc.abs()).sqrt() * dt ).tanh()
} else {
vel_t * ( ( revert_fak ).atanh() + acc.signum() * (c * acc.abs()).sqrt() * dt ).tanh()
};
//physics
let distance_last = mass / c * ( ( ( old_vel * (c/acc / mass).sqrt()).atanh() ).cosh() ).ln();
@ -358,7 +362,7 @@ fn physics_theory() -> Result<(), Box<dyn Error>> {
let ending = ((i+1) as f64 *dt * 10.0).round() as i64;
let line = format!("[{:0>2.1}]: move_dir: {:0>1.1}, over_vel_keep: {:0>4.4}, acc: {:0>4.4}, vel: {:0>4.4}, dist: {:0>7.4}, dist: {:0>7.4}, pos: {:0>7.4}, c: {:0>4.4}", (i+1) as f64 *dt, move_dir, over_vel_keep, acc, vel, distance_last, distance, pos, c);
let line = format!("[{:0>2.1}]: move_dir: {:0>1.1}, acc: {:0>4.4}, revert_fak: {:0>4.4}, vel: {:0>4.4}, dist: {:0>7.4}, dist: {:0>7.4}, pos: {:0>7.4}, c: {:0>4.4}", (i+1) as f64 *dt, move_dir, acc, revert_fak, vel, distance_last, distance, pos, c);
if ending % 10 == 0 {
println!("\x1b[91m{}\x1b[0m", line)
} else if ending % 2 != 0 {