From f4e5c34fde35e5fe2eaa71d0f9d6fb5a7abb1d3d Mon Sep 17 00:00:00 2001
From: Aaron Fenyes <aaron.fenyes@fareycircles.ooo>
Date: Mon, 19 May 2025 18:54:45 -0700
Subject: [PATCH] Add a trait method to normalize representations

This corrects the dispatching of the normalization routine for spheres,
and it adds a (perhaps redundant) normalization routine for points.
---
 app-proto/src/assembly.rs | 30 ++++++++++++++++--------------
 app-proto/src/engine.rs   | 15 +++++++++++++++
 2 files changed, 31 insertions(+), 14 deletions(-)

diff --git a/app-proto/src/assembly.rs b/app-proto/src/assembly.rs
index e48b802..0aa6dab 100644
--- a/app-proto/src/assembly.rs
+++ b/app-proto/src/assembly.rs
@@ -1,6 +1,5 @@
 use nalgebra::{DMatrix, DVector, DVectorView};
 use std::{
-    any::{Any, TypeId},
     cell::Cell,
     collections::{BTreeMap, BTreeSet},
     cmp::Ordering,
@@ -19,6 +18,8 @@ use crate::{
         Q,
         change_half_curvature,
         local_unif_to_std,
+        normalize_mut_point,
+        normalize_mut_sphere,
         point,
         realize_gram,
         sphere,
@@ -107,6 +108,9 @@ pub trait Element: Serial + ProblemPoser + DisplayItem {
     // element is responsible for keeping this set up to date
     fn regulators(&self) -> Signal<BTreeSet<Rc<dyn Regulator>>>;
     
+    // normalize a representation vector for this kind of element
+    fn normalize_mut_rep(&self, rep: &mut DVector<f64>);
+    
     // the configuration matrix column index that was assigned to the element
     // last time the assembly was realized, or `None` if the element has never
     // been through a realization
@@ -221,6 +225,10 @@ impl Element for Sphere {
         self.regulators
     }
     
+    fn normalize_mut_rep(&self, rep: &mut DVector<f64>) {
+        normalize_mut_sphere(rep);
+    }
+    
     fn column_index(&self) -> Option<usize> {
         self.column_index.get()
     }
@@ -313,6 +321,10 @@ impl Element for Point {
         self.regulators
     }
     
+    fn normalize_mut_rep(&self, rep: &mut DVector<f64>) {
+        normalize_mut_point(rep);
+    }
+    
     fn column_index(&self) -> Option<usize> {
         self.column_index.get()
     }
@@ -782,24 +794,14 @@ impl Assembly {
         
         // step the assembly along the deformation. this changes the elements'
         // normalizations, so we restore those afterward
-        /* KLUDGE */
-        // for now, we only restore the normalizations of spheres
         for elt in self.elements.get_clone_untracked() {
             elt.representation().update_silent(|rep| {
                 match elt.column_index() {
                     Some(column_index) => {
-                        // step the assembly along the deformation
+                        // step the element along the deformation and then
+                        // restore its normalization
                         *rep += motion_proj.column(column_index);
-                        
-                        if elt.type_id() == TypeId::of::<Sphere>() {
-                            // restore normalization by contracting toward the
-                            // last coordinate axis
-                            let q_sp = rep.fixed_rows::<3>(0).norm_squared();
-                            let half_q_lt = -2.0 * rep[3] * rep[4];
-                            let half_q_lt_sq = half_q_lt * half_q_lt;
-                            let scaling = half_q_lt + (q_sp + half_q_lt_sq).sqrt();
-                            rep.fixed_rows_mut::<4>(0).scale_mut(1.0 / scaling);
-                        }
+                        elt.normalize_mut_rep(rep);
                     },
                     None => {
                         console::log_1(&JsValue::from(
diff --git a/app-proto/src/engine.rs b/app-proto/src/engine.rs
index b0fa23d..7bc2bdc 100644
--- a/app-proto/src/engine.rs
+++ b/app-proto/src/engine.rs
@@ -34,6 +34,21 @@ pub fn sphere_with_offset(dir_x: f64, dir_y: f64, dir_z: f64, off: f64, curv: f6
     ])
 }
 
+// normalize a sphere's representation vector by contracting toward the last
+// coordinate axis
+pub fn normalize_mut_sphere(rep: &mut DVector<f64>) {
+    let q_sp = rep.fixed_rows::<3>(0).norm_squared();
+    let half_q_lt = -2.0 * rep[3] * rep[4];
+    let half_q_lt_sq = half_q_lt * half_q_lt;
+    let scaling = half_q_lt + (q_sp + half_q_lt_sq).sqrt();
+    rep.fixed_rows_mut::<4>(0).scale_mut(1.0 / scaling);
+}
+
+// normalize a point's representation vector by scaling
+pub fn normalize_mut_point(rep: &mut DVector<f64>) {
+    rep.scale_mut(0.5 / rep[3]);
+}
+
 // given a sphere's representation vector, change the sphere's half-curvature to
 // `half-curv` and then restore normalization by contracting the representation
 // vector toward the curvature axis