From 8098a9e8ed98914658192204b3a53d147d6f12cd Mon Sep 17 00:00:00 2001
From: haroonq <29288912+haroonq@users.noreply.github.com>
Date: Thu, 5 Oct 2023 11:16:52 +0100
Subject: [PATCH] Allow BufferView indices to be unspecified.

Allow BufferView indices for element array buffers to be unspecified to support some extensions.

Note that this is similar to how invalid array buffers are handled in order to support, for example, sparse morph targets.
---
 tiny_gltf.h | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/tiny_gltf.h b/tiny_gltf.h
index 2480c83..0b4a1d9 100644
--- a/tiny_gltf.h
+++ b/tiny_gltf.h
@@ -6145,20 +6145,22 @@ bool TinyGLTF::LoadFromString(Model *model, std::string *err, std::string *warn,
           return false;
         }
 
-        auto bufferView =
+        const auto bufferView =
             model->accessors[size_t(primitive.indices)].bufferView;
-        if (bufferView < 0 || size_t(bufferView) >= model->bufferViews.size()) {
+        if (bufferView < 0) {
+          // skip, bufferView could be null(-1) for certain extensions
+        } else if (size_t(bufferView) >= model->bufferViews.size()) { 
           if (err) {
             (*err) += "accessor[" + std::to_string(primitive.indices) +
                       "] invalid bufferView";
           }
           return false;
+        } else {
+          model->bufferViews[size_t(bufferView)].target =
+              TINYGLTF_TARGET_ELEMENT_ARRAY_BUFFER;
+          // we could optionally check if accessors' bufferView type is Scalar, as
+          // it should be
         }
-
-        model->bufferViews[size_t(bufferView)].target =
-            TINYGLTF_TARGET_ELEMENT_ARRAY_BUFFER;
-        // we could optionally check if accessors' bufferView type is Scalar, as
-        // it should be
       }
 
       for (auto &attribute : primitive.attributes) {