From 794b4f2dd772bf3334408ad9eb76070a7c3f6f73 Mon Sep 17 00:00:00 2001
From: David Catuhe <david.catuhe@live.fr>
Date: Tue, 3 Oct 2023 12:27:31 -0700
Subject: [PATCH] Fix #14381 (#14386)

---
 .../Meshes/Node/Blocks/Sources/meshBlock.ts   | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/packages/dev/core/src/Meshes/Node/Blocks/Sources/meshBlock.ts b/packages/dev/core/src/Meshes/Node/Blocks/Sources/meshBlock.ts
index b76d9faf111..f9f608efa7a 100644
--- a/packages/dev/core/src/Meshes/Node/Blocks/Sources/meshBlock.ts
+++ b/packages/dev/core/src/Meshes/Node/Blocks/Sources/meshBlock.ts
@@ -5,6 +5,7 @@ import { RegisterClass } from "../../../../Misc/typeStore";
 import type { Mesh } from "../../../../Meshes/mesh";
 import { VertexData } from "../../../../Meshes/mesh.vertexData";
 import type { Nullable } from "../../../../types";
+import { PropertyTypeForEdition, editableInPropertyPage } from "core/Decorators/nodeDecorator";
 
 /**
  * Defines a block used to generate a user defined mesh geometry data
@@ -13,6 +14,12 @@ export class MeshBlock extends NodeGeometryBlock {
     private _mesh: Nullable<Mesh>;
     private _cachedVertexData: Nullable<VertexData> = null;
 
+    /**
+     * Gets or sets a boolean indicating that winding order needs to be reserved
+     */
+    @editableInPropertyPage("reverseWindingOrder", PropertyTypeForEdition.Boolean, "ADVANCED", { notifiers: { rebuild: true } })
+    public reverseWindingOrder = false;
+
     /**
      * Gets or sets the mesh to use to get vertex data
      */
@@ -69,6 +76,14 @@ export class MeshBlock extends NodeGeometryBlock {
         const vertexData = VertexData.ExtractFromMesh(this._mesh, false, true);
         this._cachedVertexData = null;
 
+        if (this.reverseWindingOrder && vertexData.indices) {
+            for (let index = 0; index < vertexData.indices.length; index += 3) {
+                const tmp = vertexData.indices[index];
+                vertexData.indices[index] = vertexData.indices[index + 2];
+                vertexData.indices[index + 2] = tmp;
+            }
+        }
+
         this.geometry._storedFunction = () => {
             return vertexData.clone();
         };
@@ -90,6 +105,8 @@ export class MeshBlock extends NodeGeometryBlock {
             }
         }
 
+        serializationObject.reverseWindingOrder = this.reverseWindingOrder;
+
         return serializationObject;
     }
 
@@ -99,6 +116,8 @@ export class MeshBlock extends NodeGeometryBlock {
         if (serializationObject.cachedVertexData) {
             this._cachedVertexData = VertexData.Parse(serializationObject.cachedVertexData);
         }
+
+        this.reverseWindingOrder = serializationObject.reverseWindingOrder;
     }
 }