diff --git a/src/app/pages/algorithms/cloth-icm/cloth-icm-renderer.ts b/src/app/pages/algorithms/cloth-icm/cloth-icm-renderer.ts
index caf03e9..61ccb6a 100644
--- a/src/app/pages/algorithms/cloth-icm/cloth-icm-renderer.ts
+++ b/src/app/pages/algorithms/cloth-icm/cloth-icm-renderer.ts
@@ -1,5 +1,5 @@
 import {
-  ArcRotateCamera, Color3, Color4, LinesMesh, Mesh, MeshBuilder, Scene, ShaderMaterial, StandardMaterial, Vector3, VertexBuffer, VertexData
+  ArcRotateCamera, Color3, Color4, CreateLineSystemVertexData, LinesMesh, Mesh, MeshBuilder, Scene, ShaderMaterial, StandardMaterial, Vector3, VertexBuffer, VertexData
 } from '@babylonjs/core';
 import {CLOTH_FRAGMENT_SHADER_GLSL, CLOTH_VERTEX_SHADER_GLSL} from '../cloth/cloth-glsl.shader';
 import {ClothIcmScene} from './cloth-icm-scenes';
@@ -10,8 +10,8 @@ import {DOP_SIZE} from './collision/dop18';
 import {Contour} from './collision/intersection-contours';
 import {IntersectionSet} from './collision/intersection-set';
 
-const CONTOUR_COLOR = new Color3(1, 0.1, 0.1);
-const CULLED_COLOR = new Color4(0.2, 0.9, 0.3, 1);
+const CONTOUR_COLOR = new Color3(0.1, 1, 0.2);
+const CULLED_COLOR = new Color4(0.2, 0.8, 1, 1);
 const TESTED_COLOR = new Color4(0.6, 0.6, 0.6, 1);
 const OBSTACLE_COLOR = new Color3(0.35, 0.55, 0.9);
 const GROUND_SIZE = 8;
@@ -35,7 +35,6 @@ export class ClothIcmRenderer {
   private bvhLines: LinesMesh | null = null;
   private vertexBuffer = new Float32Array(0);
   private culledRegion = new Uint8Array(0);
-  private contourShape: number[] = [];
   private bvhBoxes: BvhBox[] = [];
   private bvhPaths: Vector3[][] = [];
   private bvhPathColors: Color4[][] = [];
@@ -67,7 +66,6 @@ export class ClothIcmRenderer {
     this.obstacles.forEach(mesh => mesh.dispose());
     this.obstacleMaterial?.dispose();
     this.contourLines = null;
-    this.contourShape = [];
     this.bvhLines = null;
     this.bvhBoxes = [];
     this.bvhPaths = [];
@@ -153,31 +151,26 @@ export class ClothIcmRenderer {
 
   /**
    * The hit points come from the detection, which runs on the predicted positions before the solver moves the cloth,
-   * so the lines can be a little off the drawn cloth (up to about 0.05 m). Babylon can only update a line system in
-   * place while every line keeps its point count; otherwise the mesh is rebuilt.
+   * so the lines can be a little off the drawn cloth (up to about 0.05 m).
+   * The mesh is created once and gets new geometry every frame. Disposing and creating it again would drop its shader
+   * (reference counted) and recompile it; the line shader compiles asynchronously, so a mesh whose point layout changes
+   * every frame (the drop scene) was never ready to draw.
    */
   private updateContourLines(scene: Scene, set: IntersectionSet, contours: Contour[]): void {
     if (contours.length === 0) {
-      this.contourLines?.dispose();
-      this.contourLines = null;
-      this.contourShape = [];
+      this.contourLines?.setEnabled(false);
       return;
     }
-    const lines = contours.map(contour => this.contourPath(set, contour));
-    const shape = lines.map(line => line.length);
-    const existing = this.contourLines;
-    const sameShape = shape.length === this.contourShape.length && shape.every((length, index) => length === this.contourShape[index]);
-    if (existing && sameShape) {
-      MeshBuilder.CreateLineSystem('clothIcmContours', {lines, instance: existing});
-      return;
+    const vertexData = CreateLineSystemVertexData({lines: contours.map(contour => this.contourPath(set, contour))});
+    if (!this.contourLines) {
+      const mesh = new LinesMesh('clothIcmContours', scene);
+      mesh.color = CONTOUR_COLOR;
+      mesh.renderingGroupId = OVERLAY_RENDERING_GROUP;
+      mesh.alwaysSelectAsActiveMesh = true;
+      this.contourLines = mesh;
     }
-    this.contourLines?.dispose();
-    const mesh = MeshBuilder.CreateLineSystem('clothIcmContours', {lines, updatable: true}, scene);
-    mesh.color = CONTOUR_COLOR;
-    mesh.renderingGroupId = OVERLAY_RENDERING_GROUP;
-    mesh.alwaysSelectAsActiveMesh = true;
-    this.contourLines = mesh;
-    this.contourShape = shape;
+    vertexData.applyToMesh(this.contourLines, true);
+    this.contourLines.setEnabled(true);
   }
 
   private contourPath(set: IntersectionSet, contour: Contour): Vector3[] {