From b3d5407a26083ea94435bdb05bd0a317ed2d9b90 Mon Sep 17 00:00:00 2001
From: Sean Lilley <lilleyse@gmail.com>
Date: Wed, 17 Oct 2018 21:42:28 -0400
Subject: [PATCH] Don't discard primitives that don't match the attribute
 layout

---
 lib/loadObj.js | 51 ++++++++++++++++++++++++++++++--------------------
 1 file changed, 31 insertions(+), 20 deletions(-)

diff --git a/lib/loadObj.js b/lib/loadObj.js
index 164f423..1103e88 100644
--- a/lib/loadObj.js
+++ b/lib/loadObj.js
@@ -122,25 +122,44 @@ function loadObj(objPath, options) {
         vertexCount = 0;
     }
 
-    function useMaterial(name) {
-        var material = getName(name);
-        activeMaterial = material;
-
-        // Look to see if this material has already been used by a primitive in the mesh
+    function reusePrimitive(callback) {
         var primitives = mesh.primitives;
         var primitivesLength = primitives.length;
         for (var i = 0; i < primitivesLength; ++i) {
-            if (primitives[i].material === material) {
-                primitive = primitives[i];
-                clearVertexCache();
-                vertexCount = primitive.positions.length / 3;
-                return;
+            if (primitives[i].material === activeMaterial) {
+                if (!defined(callback) || callback(primitives[i])) {
+                    primitive = primitives[i];
+                    clearVertexCache();
+                    vertexCount = primitive.positions.length / 3;
+                    return;
+                }
             }
         }
-        // Add a new primitive with this material
         addPrimitive();
     }
 
+    function useMaterial(name) {
+        activeMaterial = getName(name);
+        reusePrimitive();
+    }
+
+    function faceAndPrimitiveMatch(uvs, normals, primitive) {
+        var faceHasUvs = uvs[0].length > 0;
+        var faceHasNormals = normals[0].length > 0;
+        var primitiveHasUvs = primitive.uvs.length > 0;
+        var primitiveHasNormals = primitive.normals.length > 0;
+        return primitiveHasUvs === faceHasUvs && primitiveHasNormals === faceHasNormals;
+    }
+
+    function checkPrimitive(uvs, normals) {
+        var firstFace = primitive.indices.length === 0;
+        if (!firstFace && !faceAndPrimitiveMatch(uvs, normals, primitive)) {
+            reusePrimitive(function(primitive) {
+                return faceAndPrimitiveMatch(uvs, normals, primitive);
+            });
+        }
+    }
+
     function getOffset(a, attributeData, components) {
         var i = parseInt(a);
         if (i < 0) {
@@ -261,16 +280,8 @@ function loadObj(objPath, options) {
     function addFace(vertices, positions, uvs, normals) {
         var i;
         var isWindingCorrect;
-        var firstFace = primitive.indices.length === 0;
-        var faceHasUvs = uvs[0].length > 0;
-        var faceHasNormals = normals[0].length > 0;
-        var primitiveHasUvs = primitive.uvs.length > 0;
-        var primitiveHasNormals = primitive.normals.length > 0;
 
-        if (!firstFace && (faceHasUvs !== primitiveHasUvs || faceHasNormals !== primitiveHasNormals)) {
-            // Discard faces that don't use the same attributes
-            return;
-        }
+        checkPrimitive(uvs, normals);
 
         if (vertices.length === 3) {
             isWindingCorrect = checkWindingCorrect(positions[0], positions[1], positions[2], normals[0]);