From 6b14e166b827fba493dec4da1a16da5c4865da44 Mon Sep 17 00:00:00 2001
From: Eric Wasylishen <ewasylishen@gmail.com>
Date: Sun, 28 Jan 2018 02:19:09 -0700
Subject: [PATCH] light: make GLM_InterpolateNormal return failure on
 degenerate input

---
 common/mathlib.cc   | 3 +++
 light/test_light.cc | 6 ++++++
 2 files changed, 9 insertions(+)

diff --git a/common/mathlib.cc b/common/mathlib.cc
index 08704772..3ad61187 100644
--- a/common/mathlib.cc
+++ b/common/mathlib.cc
@@ -704,6 +704,9 @@ std::pair<bool, qvec3f> GLM_InterpolateNormal(const std::vector<qvec3f> &points,
 {
     Q_assert(points.size() == normals.size());
     
+    if (points.size() < 3)
+        return make_pair(false, qvec3f(0));
+    
     // Step through the triangles, being careful to handle zero-size ones
 
     const qvec3f &p0 = points.at(0);
diff --git a/light/test_light.cc b/light/test_light.cc
index 35815131..dcf5c8cb 100644
--- a/light/test_light.cc
+++ b/light/test_light.cc
@@ -319,6 +319,12 @@ TEST(mathlib, ProjectPointOntoPlane) {
     EXPECT_FLOAT_EQ(10, projected[2]);
 }
 
+TEST(mathlib, InterpolateNormalsDegenerate) {
+    EXPECT_FALSE(GLM_InterpolateNormal({}, {}, qvec3f(0,0,0)).first);
+    EXPECT_FALSE(GLM_InterpolateNormal({qvec3f(0,0,0)}, {qvec3f(0,0,1)}, qvec3f(0,0,0)).first);
+    EXPECT_FALSE(GLM_InterpolateNormal({qvec3f(0,0,0), qvec3f(10,0,0)}, {qvec3f(0,0,1), qvec3f(0,0,1)}, qvec3f(0,0,0)).first);
+}
+
 TEST(mathlib, InterpolateNormals) {
     // This test relies on the way GLM_InterpolateNormal is implemented