diff --git a/examples/boundary_conditions.rs b/examples/boundary_conditions.rs
index 9c463fa..a0609fc 100644
--- a/examples/boundary_conditions.rs
+++ b/examples/boundary_conditions.rs
@@ -3,9 +3,9 @@ use coremem::{Driver, mat};
 fn main() {
     coremem::init_logging();
     let width = 201;
-    let boundary = 20;
+    let boundary = 50;
     let mut driver = Driver::new(width, width, 1e-3 /* feature size */);
-    driver.add_y4m_renderer(&*format!("boundary_conditions_upml-{}.y4m", boundary));
+    driver.add_y4m_renderer(&*format!("boundary_conditions_upml_round-{}.y4m", boundary));
     // driver.add_term_renderer();
 
     //driver.add_boundary(boundary, 0.1);
diff --git a/src/driver.rs b/src/driver.rs
index 58e1132..b369a5e 100644
--- a/src/driver.rs
+++ b/src/driver.rs
@@ -76,22 +76,32 @@ impl Driver {
 
     pub fn add_upml_boundary(&mut self, thickness: u32) {
         // Based on explanation here (slide 63): https://empossible.net/wp-content/uploads/2020/01/Lecture-The-Perfectly-Matched-Layer.pdf
-        for inset in 0..thickness {
-            let depth = thickness - inset;
-            let conductivity = 0.5 * consts::EPS0 / self.state.timestep() * (depth as Flt/thickness as Flt).powf(3.0);
-            for x in inset..self.state.width() - inset {
-                let conductor = mat::Static::anisotropic_conductor(Vec3::new(0.0, conductivity, 0.0));
-                // left
-                *self.state.get_mut(x, inset).mat_mut() = conductor.clone().into();
-                // right
-                *self.state.get_mut(x, self.state.height() - 1 - inset).mat_mut() = conductor.into();
-            }
-            for y in inset..self.state.height() - inset {
-                let conductor = mat::Static::anisotropic_conductor(Vec3::new(conductivity, 0.0, 0.0));
-                // top
-                *self.state.get_mut(inset, y).mat_mut() = conductor.clone().into();
-                // bottom
-                *self.state.get_mut(self.state.width() - 1 - inset, y).mat_mut() = conductor.into();
+        let h = self.state.height();
+        let w = self.state.width();
+        for y in 0..h {
+            for x in 0..w {
+                let depth_x = if x < thickness {
+                    thickness - x
+                } else if x >= w - thickness {
+                    w - x
+                } else {
+                    0
+                };
+                let depth_y = if y < thickness {
+                    thickness - y
+                } else if y >= h - thickness {
+                    h - y
+                } else {
+                    0
+                };
+
+                if depth_x > 0 || depth_y > 0 {
+                    let scale = 0.5 * consts::EPS0 / self.state.timestep();
+                    let cond_x = scale * (depth_x as Flt/thickness as Flt).powf(3.0);
+                    let cond_y = scale * (depth_y as Flt/thickness as Flt).powf(3.0);
+                    let conductor = mat::Static::anisotropic_conductor(Vec3::new(cond_x, cond_y, 0.0));
+                    *self.state.get_mut(x, y).mat_mut() = conductor.into();
+                }
             }
         }
     }