From a41edcb25e50a0064492067360748aaf857822f0 Mon Sep 17 00:00:00 2001
From: Brandon DeRosier <bdero@google.com>
Date: Sat, 3 Dec 2022 17:56:27 -0800
Subject: [PATCH] [Impeller] Add Quaternion version of Matrix::MakeRotation

---
 impeller/geometry/geometry_unittests.cc | 20 ++++++++++++++++++++
 impeller/geometry/matrix.h              | 25 +++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/impeller/geometry/geometry_unittests.cc b/impeller/geometry/geometry_unittests.cc
index 95a0287eef600..f60cf50bfeaeb 100644
--- a/impeller/geometry/geometry_unittests.cc
+++ b/impeller/geometry/geometry_unittests.cc
@@ -265,6 +265,26 @@ TEST(GeometryTest, MatrixVectorMultiplication) {
   }
 }
 
+TEST(GeometryTest, MatrixMakeRotationFromQuaternion) {
+  {
+    auto matrix = Matrix::MakeRotation(Quaternion({1, 0, 0}, kPiOver2));
+    auto expected = Matrix::MakeRotationX(Radians(kPiOver2));
+    ASSERT_MATRIX_NEAR(matrix, expected);
+  }
+
+  {
+    auto matrix = Matrix::MakeRotation(Quaternion({0, 1, 0}, kPiOver2));
+    auto expected = Matrix::MakeRotationY(Radians(kPiOver2));
+    ASSERT_MATRIX_NEAR(matrix, expected);
+  }
+
+  {
+    auto matrix = Matrix::MakeRotation(Quaternion({0, 0, 1}, kPiOver2));
+    auto expected = Matrix::MakeRotationZ(Radians(kPiOver2));
+    ASSERT_MATRIX_NEAR(matrix, expected);
+  }
+}
+
 TEST(GeometryTest, MatrixTransformDirection) {
   {
     auto matrix = Matrix::MakeTranslation({100, 100, 100}) *
diff --git a/impeller/geometry/matrix.h b/impeller/geometry/matrix.h
index 9829317deb939..c739dae66faa5 100644
--- a/impeller/geometry/matrix.h
+++ b/impeller/geometry/matrix.h
@@ -122,6 +122,31 @@ struct Matrix {
     // clang-format on
   }
 
+  static Matrix MakeRotation(Quaternion q) {
+    // clang-format off
+    return Matrix(
+      1.0 - 2.0 * q.y * q.y - 2.0 * q.z * q.z,
+      2.0 * q.x * q.y + 2.0 * q.z * q.w,
+      2.0 * q.x * q.z - 2.0 * q.y * q.w,
+      0.0,
+
+      2.0 * q.x * q.y - 2.0 * q.z * q.w,
+      1.0 - 2.0 * q.x * q.x - 2.0 * q.z * q.z,
+      2.0 * q.y * q.z + 2.0 * q.x * q.w,
+      0.0,
+
+      2.0 * q.x * q.z + 2.0 * q.y * q.w,
+      2.0 * q.y * q.z - 2.0 * q.x * q.w,
+      1.0 - 2.0 * q.x * q.x - 2.0 * q.y * q.y,
+      0.0,
+
+      0.0,
+      0.0,
+      0.0,
+      1.0);
+    // clang-format on
+  }
+
   static Matrix MakeRotation(Scalar radians, const Vector4& r) {
     const Vector4 v = r.Normalize();