SPS .recalculateNormals

defaults to true, so no change in default behaviour.
if set to false, keeps the normals from the added shape mesh instead of
recalculating all normals.
Useful if normals of the shape are not perpendicular to the faces. (like
a volumetric cloud particle)

src/Particles/babylon.solidParticleSystem.ts

@@ -19,6 +19,10 @@
         */
         public billboard: boolean = false;
         /**
+         * Recompute normals when adding a shape
+         */
+        public recomputeNormals: boolean = true;
+        /**
         * This a counter ofr your own usage. It's not set by any SPS functions.
         */
         public counter: number = 0;
@@ -139,7 +143,9 @@
             this._positions32 = new Float32Array(this._positions);
             this._uvs32 = new Float32Array(this._uvs);
             this._colors32 = new Float32Array(this._colors);
-            VertexData.ComputeNormals(this._positions32, this._indices, this._normals);
+            if (this.recomputeNormals) {
+                VertexData.ComputeNormals(this._positions32, this._indices, this._normals);
+            }
             this._normals32 = new Float32Array(this._normals);
             this._fixedNormal32 = new Float32Array(this._normals);
             var vertexData = new VertexData();
@@ -187,6 +193,7 @@
             var meshInd = mesh.getIndices();
             var meshUV = mesh.getVerticesData(VertexBuffer.UVKind);
             var meshCol = mesh.getVerticesData(VertexBuffer.ColorKind);
+            var meshNor = mesh.getVerticesData(VertexBuffer.NormalKind);
 
             var f: number = 0;                              // facet counter
             var totalFacets: number = meshInd.length / 3;   // a facet is a triangle, so 3 indices
@@ -252,7 +259,7 @@
                 var modelShape = new ModelShape(this._shapeCounter, shape, shapeUV, null, null);
 
                 // add the particle in the SPS
-                this._meshBuilder(this._index, shape, this._positions, facetInd, this._indices, facetUV, this._uvs, facetCol, this._colors, idx, 0, null);
+                this._meshBuilder(this._index, shape, this._positions, facetInd, this._indices, facetUV, this._uvs, facetCol, this._colors, meshNor, this._normals, idx, 0, null);
                 this._addParticle(idx, this._positions.length, modelShape, this._shapeCounter, 0);
                 // initialize the particle position
                 this.particles[this.nbParticles].position.addInPlace(barycenter);
@@ -286,10 +293,11 @@
         }
 
         // _meshBuilder : inserts the shape model in the global SPS mesh
-        private _meshBuilder(p, shape, positions, meshInd, indices, meshUV, uvs, meshCol, colors, idx, idxInShape, options): void {
+        private _meshBuilder(p, shape, positions, meshInd, indices, meshUV, uvs, meshCol, colors, meshNor, normals, idx, idxInShape, options): void {
             var i;
             var u = 0;
             var c = 0;
+            var n = 0;
 
             this._resetCopy();
             if (options && options.positionFunction) {        // call to custom positionFunction
@@ -342,6 +350,15 @@
                 colors.push(this._color.r, this._color.g, this._color.b, this._color.a);
                 c += 4;
 
+                if (!this.recomputeNormals && meshNor) {
+                    this._normal.x = meshNor[n];
+                    this._normal.y = meshNor[n + 1];
+                    this._normal.z = meshNor[n + 2];
+                    Vector3.TransformCoordinatesToRef(this._normal, this._rotMatrix, this._normal);
+                    normals.push(this._normal.x, this._normal.y, this._normal.z);
+                    n += 3;
+                }
+
             }
 
             for (i = 0; i < meshInd.length; i++) {
@@ -393,6 +410,7 @@
             var meshInd = mesh.getIndices();
             var meshUV = mesh.getVerticesData(VertexBuffer.UVKind);
             var meshCol = mesh.getVerticesData(VertexBuffer.ColorKind);
+            var meshNor = mesh.getVerticesData(VertexBuffer.NormalKind);
 
             var shape = this._posToShape(meshPos);
             var shapeUV = this._uvsToShapeUV(meshUV);
@@ -405,7 +423,7 @@
             // particles
             var idx = this.nbParticles;
             for (var i = 0; i < nb; i++) {
-                this._meshBuilder(this._index, shape, this._positions, meshInd, this._indices, meshUV, this._uvs, meshCol, this._colors, idx, i, options);
+                this._meshBuilder(this._index, shape, this._positions, meshInd, this._indices, meshUV, this._uvs, meshCol, this._colors, meshNor, this._normals, idx, i, options);
                 if (this._updatable) {
                     this._addParticle(idx, this._positions.length, modelShape, this._shapeCounter, i);
                 }