From 967daa595dd3b3ffd7564d6848319e4fb13f6ded Mon Sep 17 00:00:00 2001
From: Aaron Fenyes <aaron.fenyes@fareycircles.ooo>
Date: Wed, 18 Dec 2024 00:34:25 -0800
Subject: [PATCH] Deform fresh elements too

Implement deformation of elements that haven't gone through realization.
---
 app-proto/src/assembly.rs | 51 +++++++++++++++++++++------------------
 1 file changed, 27 insertions(+), 24 deletions(-)

diff --git a/app-proto/src/assembly.rs b/app-proto/src/assembly.rs
index ec480ac..fa0a48c 100644
--- a/app-proto/src/assembly.rs
+++ b/app-proto/src/assembly.rs
@@ -33,8 +33,8 @@ pub struct Element {
     pub serial: u64,
     
     // the configuration matrix column index that was assigned to this element
-    // last time the assembly was realized, or `None` if the assembly has never
-    // been realized with this element in it
+    // last time the assembly was realized, or `None` if the element has never
+    // been through a realization
     column_index: Option<usize>
 }
 
@@ -160,13 +160,6 @@ impl Assembly {
         let id = elt.id.clone();
         let key = self.elements.update(|elts| elts.insert(elt));
         self.elements_by_id.update(|elts_by_id| elts_by_id.insert(id, key));
-        
-        // realize to update the tangent space
-        /* KLUDGE */
-        // since the newly inserted element is unconstrained, we should be able
-        // to update the tangent space without recomputing the Hessian and its
-        // eigendecomposition
-        self.realize();
     }
     
     pub fn try_insert_element(&self, elt: Element) -> bool {
@@ -300,35 +293,43 @@ impl Assembly {
     
     pub fn deform(&self, motion: AssemblyMotion) {
         /* KLUDGE */
-        // when the tangent space is zero, we currently need to avoid calling
-        // its `proj` method, because it will panic rather than returning zero.
-        // in the future, we'll want a more intentionally designed system for
-        // handling this case
-        if self.tangent.with(|tan| tan.dim() <= 0) {
+        // when the tangent space is zero, deformation won't do anything, but
+        // the attempt to deform should be registered in the UI. this console
+        // message will do for now
+        if self.tangent.with(|tan| tan.dim() <= 0 && tan.assembly_dim() > 0) {
             console::log_1(&JsValue::from("The assembly is rigid"));
-            return;
         }
         
         const ELEMENT_DIM: usize = 5;
-        let assembly_dim = self.tangent.with(|tan| tan.assembly_dim());
+        let assembly_dim = self.elements.with(|elts| elts.len());
         let mut motion_proj = DMatrix::zeros(ELEMENT_DIM, assembly_dim);
+        let tan_assembly_dim = self.tangent.with(|tan| tan.assembly_dim());
         
         // project the element motions onto the tangent space of the solution
         // variety, and sum them to get a deformation of the whole assembly
+        let mut next_column_index = tan_assembly_dim;
         for elt_motion in motion {
             match self.elements.with_untracked(|elts| elts[elt_motion.key].column_index) {
                 Some(column_index) => {
-                    motion_proj += self.tangent.with(
+                    let mut target_columns = motion_proj.columns_mut(0, tan_assembly_dim);
+                    target_columns += self.tangent.with(
                         |tan| tan.proj(&elt_motion.velocity, column_index)
                     )
                 },
                 None => {
-                    console::log_1(&JsValue::from(
-                        format!(
-                            "Ignoring motion of fresh element \"{}\"",
-                            self.elements.with_untracked(|elts| elts[elt_motion.key].id.clone())
-                        )
-                    ))
+                    // give the element a column index, even though it's never
+                    // been through a realization, and add its motion to that
+                    // column of the projected motion. this puts the element
+                    // column indices out of sync with the saved tangent space,
+                    // but that's okay: the realization we do to get back onto
+                    // the solution variety will re-index the elements and
+                    // recompute the tangent space
+                    let mut target_column = motion_proj.column_mut(next_column_index);
+                    target_column += elt_motion.velocity;
+                    self.elements.update_silent(
+                        |elts| elts[elt_motion.key].column_index = Some(next_column_index)
+                    );
+                    next_column_index += 1;
                 }
             }
         }
@@ -355,7 +356,9 @@ impl Assembly {
             });
         }
         
-        // bring the configuration back onto the solution variety
+        // bring the configuration back onto the solution variety. this also
+        // gets the elements' column indices and the saved tangent space back in
+        // sync
         self.realize();
     }
 }
\ No newline at end of file