From d10dec18034bd17f01d43f0029113258b69a6776 Mon Sep 17 00:00:00 2001
From: Eric Wasylishen <ewasylishen@gmail.com>
Date: Fri, 12 Jan 2018 00:36:12 -0700
Subject: [PATCH] light: make GLM_PolyCentroid accept degenerate faces (todo:
 must rename these)

---
 common/mathlib.cc   |  8 ++++++++
 light/test_light.cc | 16 ++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/common/mathlib.cc b/common/mathlib.cc
index 477b8f0f..08704772 100644
--- a/common/mathlib.cc
+++ b/common/mathlib.cc
@@ -24,6 +24,7 @@
 
 #include <tuple>
 #include <map>
+#include <cmath>
 
 #include <common/qvec.hh>
 
@@ -596,6 +597,13 @@ float GLM_PolyArea(const std::vector<qvec3f> &points)
 
 qvec3f GLM_PolyCentroid(const std::vector<qvec3f> &points)
 {
+    if (points.size() == 0)
+        return qvec3f(NAN);
+    else if (points.size() == 1)
+        return points.at(0);
+    else if (points.size() == 2)
+        return (points.at(0) + points.at(1)) / 2.0;
+
     Q_assert(points.size() >= 3);
     
     qvec3f poly_centroid(0);
diff --git a/light/test_light.cc b/light/test_light.cc
index 8eeb2874..35815131 100644
--- a/light/test_light.cc
+++ b/light/test_light.cc
@@ -181,6 +181,22 @@ TEST(mathlib, ClosestPointOnPolyBoundary) {
     EXPECT_EQ(make_pair(0, qvec3f(0,0,0)), GLM_ClosestPointOnPolyBoundary(poly, qvec3f(-1,-1,0)));
 }
 
+TEST(mathlib, PolygonCentroid_empty) {
+    const qvec3f res = GLM_PolyCentroid({});
+    
+    for (int i=0; i<3; i++) {
+    	EXPECT_TRUE(std::isnan(res[i]));
+    }
+}
+
+TEST(mathlib, PolygonCentroid_point) {
+    EXPECT_EQ(qvec3f(1,1,1), GLM_PolyCentroid({qvec3f(1,1,1)}));
+}
+
+TEST(mathlib, PolygonCentroid_line) {
+    EXPECT_EQ(qvec3f(1,1,1), GLM_PolyCentroid({qvec3f(0,0,0), qvec3f(2,2,2)}));
+}
+
 TEST(mathlib, PolygonCentroid) {
     // poor test.. but at least checks that the colinear point is treated correctly
     const vector<qvec3f> poly {