(sys_mimic) Exponential easing

src/blueprints/blu_camera_follow.ts

@@ -9,7 +9,7 @@ import {Game} from "../game.js";
 export function blueprint_camera_follow(game: Game) {
     return [
         transform(),
-        mimic(first_named(game.World, "camera anchor")),
+        mimic(first_named(game.World, "camera anchor"), 0.2),
         children([
             transform(
                 [50, 50, 50],

src/components/com_mimic.ts

@@ -15,17 +15,17 @@ import {Has} from "../world.js";
 export interface Mimic {
     /** Entity whose transform to mimic. */
     Target: Entity;
-    /** How laggy vs. precise is the mimicking [0-1]. */
+    /** The stiffness of the follower, eased exponentially. */
     Stiffness: number;
 }
 
 /**
  * Add `Mimic` to an entity.
  *
  * @param target Entity whose transform to mimic.
- * @param stiffness How laggy vs. precise is the mimicking [0-1].
+ * @param stiffness The time in seconds that it takes the followers to get closer to the target by a factor of e.
  */
-export function mimic(target: Entity, stiffness: number = 0.1) {
+export function mimic(target: Entity, stiffness: number = 1) {
     return (game: Game, entity: Entity) => {
         game.World.Signature[entity] |= Has.Mimic;
         game.World.Mimic[entity] = {

src/systems/sys_mimic.ts

@@ -17,15 +17,15 @@ const QUERY = Has.Transform | Has.Mimic;
 export function sys_mimic(game: Game, delta: number) {
     for (let ent = 0; ent < game.World.Signature.length; ent++) {
         if ((game.World.Signature[ent] & QUERY) === QUERY) {
-            update(game, ent);
+            update(game, ent, delta);
         }
     }
 }
 
 let target_position: Vec3 = [0, 0, 0];
 let target_rotation: Quat = [0, 0, 0, 1];
 
-function update(game: Game, entity: Entity) {
+function update(game: Game, entity: Entity, delta: number) {
     // Follower must be a top-level transform for this to work.
     let transform = game.World.Transform[entity];
     let mimic = game.World.Mimic[entity];
@@ -34,8 +34,10 @@ function update(game: Game, entity: Entity) {
     mat4_get_translation(target_position, target_transform.World);
     mat4_get_rotation(target_rotation, target_transform.World);
 
-    vec3_lerp(transform.Translation, transform.Translation, target_position, mimic.Stiffness);
-    quat_slerp(transform.Rotation, transform.Rotation, target_rotation, mimic.Stiffness);
+    // https://lisyarus.github.io/blog/programming/2023/02/21/exponential-smoothing.html
+    let t = 1 - Math.exp(-delta / mimic.Stiffness);
+    vec3_lerp(transform.Translation, transform.Translation, target_position, t);
+    quat_slerp(transform.Rotation, transform.Rotation, target_rotation, t);
 
     game.World.Signature[entity] |= Has.Dirty;
 }