Deform the assembly

This seems like a good starting point, even though the code is messy and
the deformation routine has some numerical quirks. Note that the translation
direction is mixed up: the keys are for x, but the velocity field is for z.

app-proto/src/engine.rs

@@ -87,6 +87,7 @@ impl PartialMatrix {
 
 // --- configuration subspaces ---
 
+#[derive(Clone)]
 pub struct ConfigSubspace(Vec<DMatrix<f64>>);
 
 impl ConfigSubspace {
@@ -99,7 +100,7 @@ impl ConfigSubspace {
     // of the kernel if its eigenvalue is smaller than the constant `THRESHOLD`
     fn symmetric_kernel(a: DMatrix<f64>, assembly_dim: usize) -> ConfigSubspace {
         const ELEMENT_DIM: usize = 5;
-        const THRESHOLD: f64 = 1.0e-9;
+        const THRESHOLD: f64 = 1.0e-4;
         let eig = SymmetricEigen::new(a);
         let eig_vecs = eig.eigenvectors.column_iter();
         let eig_pairs = eig.eigenvalues.iter().zip(eig_vecs);
@@ -110,15 +111,23 @@ impl ConfigSubspace {
                 )
             )
         );
+        console::log_1(&JsValue::from(
+            format!("Hessian eigenvalues: {}", eig.eigenvalues)
+        )); /* DEBUG */
         ConfigSubspace(basis.collect())
     }
     
+    pub fn dim(&self) -> usize {
+        let ConfigSubspace(basis) = self;
+        basis.len()
+    }
+    
     // find the projection onto this subspace of the motion where the element
     // with the given column index has velocity `v`
     /* TO DO */
     // for the zero subspace, this method's behavior doesn't match its name: it
     // panics rather than returning zero
-    fn proj(&self, v: &DVectorView<f64>, column_index: usize) -> DMatrix<f64> {
+    pub fn proj(&self, v: &DVectorView<f64>, column_index: usize) -> DMatrix<f64> {
         let ConfigSubspace(basis) = self;
         basis.into_iter().map(
             |b| b.column(column_index).dot(&v) * b