app-proto/src/assembly.rs

@@ -5,7 +5,7 @@ use std::{collections::BTreeSet, sync::atomic::{AtomicU64, Ordering}};
 use sycamore::prelude::*;
 use web_sys::{console, wasm_bindgen::JsValue}; /* DEBUG */
 
-use crate::engine::{realize_gram, ConfigSubspace, PartialMatrix};
+use crate::engine::{realize_gram, ConfigSubspace, PartialMatrix, Q};
 
 // the types of the keys we use to access an assembly's elements and constraints
 pub type ElementKey = usize;
@@ -312,12 +312,16 @@ impl Assembly {
             motion_proj += self.tangent.with(|tan| tan.proj(&elt_motion, column_index));
         }
         
-        // step the configuration linearly along the tangent space of the
-        // solution variety
+        // step each element along the mass shell geodesic that matches its
+        // velocity in the deformation found above
+        /* KLUDGE */
+        // since our test assemblies only involve spheres, we assume that every
+        // element is on the 1 mass shell
         for (_, elt) in self.elements.get_clone_untracked() {
             elt.representation.update_silent(|rep| {
                 let rep_next = &*rep + motion_proj.column(elt.column_index);
-                rep.set_column(0, &rep_next);
+                let normalizer = rep_next.dot(&(&*Q * &rep_next));
+                rep.set_column(0, &(rep_next / normalizer));
             });
         }