diff --git a/src/lib/components/App.svelte b/src/lib/components/App.svelte
index 5a33c8d..4a6bbd8 100644
--- a/src/lib/components/App.svelte
+++ b/src/lib/components/App.svelte
@@ -14,7 +14,7 @@
 </Canvas>
 
 <div class="controls">
-	<input type="range" min="0" max="1" step="0.01" bind:value={showSlices} orient="vertical" />
+	<input type="range" min="0" max="1" step="0.001" bind:value={showSlices} orient="vertical" />
 </div>
 
 {#if $progress !== undefined}
@@ -28,6 +28,7 @@
 
 <style lang="scss">
 	input[type='range'] {
+		height: 80%;
 	}
 
 	.controls {
diff --git a/src/lib/components/Scene.svelte b/src/lib/components/Scene.svelte
index de9301e..9ef3a39 100644
--- a/src/lib/components/Scene.svelte
+++ b/src/lib/components/Scene.svelte
@@ -10,7 +10,8 @@
 		Mesh,
 		DoubleSide,
 		Color,
-		BufferGeometryLoader
+		BufferGeometryLoader,
+		ConeGeometry
 	} from 'three';
 	import { writable } from 'svelte/store';
 	import { onDestroy, onMount } from 'svelte';
@@ -63,7 +64,6 @@
 	export let maxNonPlanarAngle = MathUtils.degToRad(20);
 	export let bedNormal = new Vector3(0, 0, 1);
 
-	let mesh: Mesh;
 	let layers = writable<Layer[]>([]);
 
 	const stl: AsyncWritable<BufferGeometry> = useLoader(STLLoader).load('/benchy.stl');
@@ -113,8 +113,8 @@
 	{/if}
 {/each}
 
-{#if $stl && false}
-	<T.Mesh geometry={$stl} bind:ref={mesh}>
+{#if $stl}
+	<T.Mesh geometry={$stl} position.y={40}>
 		<T.MeshNormalMaterial />
 	</T.Mesh>
 {/if}
diff --git a/src/lib/slicer/worker.ts b/src/lib/slicer/worker.ts
index fcde595..e4a0fdb 100644
--- a/src/lib/slicer/worker.ts
+++ b/src/lib/slicer/worker.ts
@@ -153,14 +153,14 @@ function slice({
 		const positions: number[] = [];
 		for (let i = 0; i < nonPlanarSurfaces.length; i++) {
 			if (consumedNonPlanarSurfaces[i]) continue;
-			if (nonPlanarSurfaces[i].geometry.boundingBox!.min.z > layer) {
+			if (layer >= nonPlanarSurfaces[i].geometry.boundingBox!.min.z) {
 				consumedNonPlanarSurfaces[i] = true;
 				activeNonPlanarSurfaces.push([i, nonPlanarSurfaces[i]]);
 			}
 		}
 		deactivate: for (let i = 0; i < activeNonPlanarSurfaces.length; i++) {
 			const [index, surface] = activeNonPlanarSurfaces[i];
-			if (surface.geometry.boundingBox!.max.z <= layer) {
+			if (layer > surface.geometry.boundingBox!.max.z) {
 				activeNonPlanarSurfaces.splice(i, 1);
 				i--;