From 205e5d730927a3852cf914bcedfcc94e3f4549c2 Mon Sep 17 00:00:00 2001
From: Andrew Meadows <andrew@highfidelity.io>
Date: Wed, 31 May 2017 11:24:36 -0700
Subject: [PATCH] add unit tests and fix final bugs

---
 libraries/shared/src/GLMHelpers.cpp  |  7 ++-
 tests/shared/src/GLMHelpersTests.cpp | 74 ++++++++++++++++++++++++++++
 tests/shared/src/GLMHelpersTests.h   |  1 +
 3 files changed, 78 insertions(+), 4 deletions(-)

diff --git a/libraries/shared/src/GLMHelpers.cpp b/libraries/shared/src/GLMHelpers.cpp
index 10c73d6c6a..7ebaa11da6 100644
--- a/libraries/shared/src/GLMHelpers.cpp
+++ b/libraries/shared/src/GLMHelpers.cpp
@@ -538,12 +538,11 @@ void generateBasisVectors(const glm::vec3& primaryAxis, const glm::vec3& seconda
     uAxisOut = glm::normalize(primaryAxis);
     glm::vec3 normSecondary = glm::normalize(secondaryAxis);
 
-    // if secondaryAxis is parallel with the primaryAxis, pick another axis.
+    // if normSecondary is parallel with the primaryAxis, pick another secondary.
     const float EPSILON = 1.0e-4f;
-    if (fabsf(fabsf(glm::dot(uAxisOut, secondaryAxis)) - 1.0f) < EPSILON) {
-        // pick a better secondaryAxis.
+    if (fabsf(fabsf(glm::dot(uAxisOut, normSecondary)) - 1.0f) < EPSILON) {
         normSecondary = glm::vec3(1.0f, 0.0f, 0.0f);
-        if (fabsf(fabsf(glm::dot(uAxisOut, secondaryAxis)) - 1.0f) < EPSILON) {
+        if (fabsf(fabsf(glm::dot(uAxisOut, normSecondary)) - 1.0f) < EPSILON) {
             normSecondary = glm::vec3(0.0f, 1.0f, 0.0f);
         }
     }
diff --git a/tests/shared/src/GLMHelpersTests.cpp b/tests/shared/src/GLMHelpersTests.cpp
index b4af4729a3..83a294ee1d 100644
--- a/tests/shared/src/GLMHelpersTests.cpp
+++ b/tests/shared/src/GLMHelpersTests.cpp
@@ -140,3 +140,77 @@ void GLMHelpersTests::testSimd() {
     }
     qDebug() << "Done ";
 }
+
+void GLMHelpersTests::testGenerateBasisVectors() {
+    { // very simple case: primary along X, secondary is linear combination of X and Y
+        glm::vec3 u(1.0f, 0.0f, 0.0f);
+        glm::vec3 v(1.0f, 1.0f, 0.0f);
+        glm::vec3 w;
+
+        generateBasisVectors(u, v, u, v, w);
+
+        QCOMPARE_WITH_ABS_ERROR(u, Vectors::UNIT_X, EPSILON);
+        QCOMPARE_WITH_ABS_ERROR(v, Vectors::UNIT_Y, EPSILON);
+        QCOMPARE_WITH_ABS_ERROR(w, Vectors::UNIT_Z, EPSILON);
+    }
+
+    { // point primary along Y instead of X
+        glm::vec3 u(0.0f, 1.0f, 0.0f);
+        glm::vec3 v(1.0f, 1.0f, 0.0f);
+        glm::vec3 w;
+
+        generateBasisVectors(u, v, u, v, w);
+
+        QCOMPARE_WITH_ABS_ERROR(u, Vectors::UNIT_Y, EPSILON);
+        QCOMPARE_WITH_ABS_ERROR(v, Vectors::UNIT_X, EPSILON);
+        QCOMPARE_WITH_ABS_ERROR(w, -Vectors::UNIT_Z, EPSILON);
+    }
+
+    { // pass bad data (both vectors along Y).  The helper will guess X for secondary.
+        glm::vec3 u(0.0f, 1.0f, 0.0f);
+        glm::vec3 v(0.0f, 1.0f, 0.0f);
+        glm::vec3 w;
+
+        generateBasisVectors(u, v, u, v, w);
+
+        QCOMPARE_WITH_ABS_ERROR(u, Vectors::UNIT_Y, EPSILON);
+        QCOMPARE_WITH_ABS_ERROR(v, Vectors::UNIT_X, EPSILON);
+        QCOMPARE_WITH_ABS_ERROR(w, -Vectors::UNIT_Z, EPSILON);
+    }
+
+    { // pass bad data (both vectors along X).  The helper will guess X for secondary, fail, then guess Y.
+        glm::vec3 u(1.0f, 0.0f, 0.0f);
+        glm::vec3 v(1.0f, 0.0f, 0.0f);
+        glm::vec3 w;
+
+        generateBasisVectors(u, v, u, v, w);
+
+        QCOMPARE_WITH_ABS_ERROR(u, Vectors::UNIT_X, EPSILON);
+        QCOMPARE_WITH_ABS_ERROR(v, Vectors::UNIT_Y, EPSILON);
+        QCOMPARE_WITH_ABS_ERROR(w, Vectors::UNIT_Z, EPSILON);
+    }
+
+    { // general case for arbitrary rotation
+        float angle = 1.234f;
+        glm::vec3 axis = glm::normalize(glm::vec3(1.0f, 2.0f, 3.0f));
+        glm::quat rotation = glm::angleAxis(angle, axis);
+
+        // expected values
+        glm::vec3 x = rotation * Vectors::UNIT_X;
+        glm::vec3 y = rotation * Vectors::UNIT_Y;
+        glm::vec3 z = rotation * Vectors::UNIT_Z;
+
+        // primary is along x
+        // secondary is linear combination of x and y
+        // tertiary is unknown
+        glm::vec3 u  = 1.23f * x;
+        glm::vec3 v = 2.34f * x + 3.45f * y;
+        glm::vec3 w;
+
+        generateBasisVectors(u, v, u, v, w);
+
+        QCOMPARE_WITH_ABS_ERROR(u, x, EPSILON);
+        QCOMPARE_WITH_ABS_ERROR(v, y, EPSILON);
+        QCOMPARE_WITH_ABS_ERROR(w, z, EPSILON);
+    }
+}
diff --git a/tests/shared/src/GLMHelpersTests.h b/tests/shared/src/GLMHelpersTests.h
index acc7b533f5..030f2d477f 100644
--- a/tests/shared/src/GLMHelpersTests.h
+++ b/tests/shared/src/GLMHelpersTests.h
@@ -21,6 +21,7 @@ private slots:
     void testEulerDecomposition();
     void testSixByteOrientationCompression();
     void testSimd();
+    void testGenerateBasisVectors();
 };
 
 float getErrorDifference(const float& a, const float& b);