optimize the dilate operation

src/geom/region/mod.rs

@@ -243,31 +243,41 @@ impl Region for Wrap {
 pub struct Dilate {
     inner: Box<dyn Region>,
     rad: f32,
+    res: f32,
 }
 
 impl Dilate {
-    pub fn new<T: Region + 'static>(inner: T, rad: f32) -> Self {
-        Self { inner: Box::new(inner), rad }
+    pub fn new<T: Region + 'static>(inner: T, rad: f32, res: f32) -> Self {
+        Self { inner: Box::new(inner), rad, res }
     }
     pub fn new_iterated<T: Region + 'static>(inner: T, resolution: f32, iters: usize) -> Self {
-        let mut it = Self::new(inner, resolution);
-        for _ in 1..iters {
-            it = Self::new(it, resolution);
-        }
-        it
+        Self::new(inner, resolution * iters as f32, resolution)
     }
 }
 
 #[typetag::serde]
 impl Region for Dilate {
     fn contains(&self, p: Meters) -> bool {
-        self.inner.contains(p)
-            || self.inner.contains(p + Meters::new(self.rad, 0.0, 0.0))
-            || self.inner.contains(p + Meters::new(0.0, -self.rad, 0.0))
-            || self.inner.contains(p + Meters::new(0.0, self.rad, 0.0))
-            || self.inner.contains(p + Meters::new(0.0, -self.rad, 0.0))
-            || self.inner.contains(p + Meters::new(0.0, 0.0, self.rad))
-            || self.inner.contains(p + Meters::new(0.0, 0.0, -self.rad))
+        let small = p - Meters::new(self.rad, self.rad, self.rad);
+        let large = p + Meters::new(self.rad, self.rad, self.rad);
+        let rad_iters = (self.rad / self.res).ceil() as i32;
+        let rad_range = -rad_iters..=rad_iters;
+        let rad_sq = self.rad * self.rad;
+        for zoff in rad_range.clone() {
+            for yoff in rad_range.clone() {
+                for xoff in rad_range.clone() {
+                    let off = Meters::new(
+                        xoff as f32 * self.res,
+                        yoff as f32 * self.res,
+                        zoff as f32 * self.res,
+                    );
+                    if off.mag_sq() <= rad_sq && self.inner.contains(p + off) {
+                        return true;
+                    }
+                }
+            }
+        }
+        false
     }
 }