CurlStimulus: take axis and center directly from the Region

by taking more from the region, we'll be able to reuse common code
and also make this more testable

crates/applications/buffer_proto5/src/main.rs

@@ -429,8 +429,6 @@ fn run_sim(id: u32, p: Params, g: Geometries) -> Results {
         driver.add_stimulus(CurlStimulus::new(
             region.clone(),
             wave.clone(),
-            region.center(),
-            region.axis()
         ));
     };
 
@@ -439,8 +437,6 @@ fn run_sim(id: u32, p: Params, g: Geometries) -> Results {
         driver.add_stimulus(CurlStimulus::new(
             region.clone(),
             wave.clone(),
-            region.center(),
-            region.axis()
         ));
     };
 
@@ -449,8 +445,6 @@ fn run_sim(id: u32, p: Params, g: Geometries) -> Results {
         driver.add_stimulus(CurlStimulus::new(
             region.clone(),
             wave.clone(),
-            region.center(),
-            region.axis()
         ));
     };
 

crates/applications/multi_core_inverter/src/main.rs

@@ -94,8 +94,6 @@ fn main() {
         CurlStimulus::new(
             region.clone(),
             wave.clone(),
-            region.center(),
-            region.axis(),
         )
     };
 

crates/applications/sr_latch/src/main.rs

@@ -84,8 +84,6 @@ fn main() {
         driver.add_stimulus(CurlStimulus::new(
             region.clone(),
             wave.clone(),
-            region.center(),
-            region.axis()
         ));
     };
 

crates/coremem/src/stim.rs

@@ -1,6 +1,6 @@
 use crate::real::*;
 use crate::cross::vec::Vec3;
-use crate::geom::{Meters, Region};
+use crate::geom::{Meters, Region, Torus};
 use rand;
 
 /// field densities
@@ -150,23 +150,24 @@ impl<R: Region + Sync, T: TimeVarying3 + Sync> AbstractStimulus for Stimulus<R,
 pub struct CurlStimulus<R, T> {
     region: R,
     stim: T,
-    center: Meters,
-    axis: Meters,
 }
 
 impl<R, T> CurlStimulus<R, T> {
-    pub fn new(region: R, stim: T, center: Meters, axis: Meters) -> Self {
-        Self { region, stim, center, axis }
+    pub fn new(region: R, stim: T) -> Self {
+        Self { region, stim }
     }
 }
 
-impl<R: Region + Sync, T: TimeVarying1 + Sync> AbstractStimulus for CurlStimulus<R, T> {
+// TODO: don't require Torus: parameterize over anything which HasCrossSection
+impl<T: TimeVarying1 + Sync> AbstractStimulus for CurlStimulus<Torus, T> {
     fn at(&self, t_sec: f32, pos: Meters) -> Fields {
         if self.region.contains(pos) {
+            let center = self.region.center();
+            let axis = self.region.axis();
             let FieldMags { e, h } = self.stim.at(t_sec);
-            let from_center_to_point = *pos - *self.center;
+            let from_center_to_point = *pos - *center;
             // TODO: is this inverted?
-            let rotational = from_center_to_point.cross(*self.axis);
+            let rotational = from_center_to_point.cross(*axis);
             let impulse_e = rotational.with_mag(e.cast()).unwrap_or_default();
             let impulse_h = rotational.with_mag(h.cast()).unwrap_or_default();
             Fields {