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Simplify buoyancy for performance reasons

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This commit is contained in:
Ludvig Böklin 2021-04-21 16:18:46 +02:00
parent b10718c568
commit a1744182b3
1 changed files with 5 additions and 23 deletions
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28
common/systems/src/phys.rs
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@ -22,36 +22,18 @@ use specs::{
Entities, Entity, Join, ParJoin, Read, ReadExpect, ReadStorage, SystemData, Write, WriteExpect,
WriteStorage,
};
use std::{f32::consts::PI, ops::Range};
use std::ops::Range;
use vek::*;
/// The density of the fluid as a function of submersion ratio in given fluid
/// where it is assumed that any unsubmersed part is is air.
// This is a pretty silly way of doing it as it assumes everything is spherical
// in shape and uniform in mass distribution, but the result feels good enough.
// TODO: Make the shape a capsule?
// TODO: Better suited partial submersion curve?
fn fluid_density(height: f32, fluid: &Fluid) -> Density {
// If depth is less than our height (partial submersion), remove
// fluid density based on the ratio of displacement to full volume.
// The displacement is modelled as a gradually submersed sphere.
let immersion = fluid.depth().map_or(1.0, |depth| {
if height < depth {
1.0
} else {
let hemisphere_filled_vol = |r: f32, h: f32| -> f32 {
let r_ = (r.powi(2) - (r - h).powi(2)).sqrt();
(1.0 / 6.0) * PI * h * (3.0 * r_.powi(2) + h.powi(2))
};
let hemisphere_vol = |r: f32| -> f32 { (2.0 / 3.0) * PI * r.powi(3) };
let r = height / 2.0;
let sphere_vol = 2.0 * hemisphere_vol(r);
if depth < r {
hemisphere_filled_vol(r, depth) / sphere_vol
} else {
1.0 - hemisphere_filled_vol(r, height - depth) / sphere_vol
}
}
});
let immersion = fluid
.depth()
.map_or(1.0, |depth| (depth / height).clamp(0.0, 1.0));
Density(fluid.density().0 * immersion + AIR_DENSITY * (1.0 - immersion))
}