Correct normal computation for inverted polygons.

cc/quads/draw_polygon_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // We would like to use M_PI on windows too.
 #ifdef _WIN32
 #define _USE_MATH_DEFINES
 #endif
 
 #include <stddef.h>
@@ skipping 12 matching lines @@
 void DrawPolygon::RecomputeNormalForTesting() {
   ConstructNormal();
 }
 #endif
 
 namespace {
 
 #define CREATE_NEW_DRAW_POLYGON(name, points_vector, normal, polygon_id) \
   DrawPolygon name(NULL, points_vector, normal, polygon_id)
 
-#define CREATE_TEST_DRAW_POLYGON(name, points_vector, polygon_id)             \
-  DrawPolygon name(NULL, points_vector, gfx::Vector3dF(1, 2, 3), polygon_id); \
+#define CREATE_TEST_DRAW_FORWARD_POLYGON(name, points_vector, id)        \
+  DrawPolygon name(NULL, points_vector, gfx::Vector3dF(0, 0, 1.0f), id); \
+  name.RecomputeNormalForTesting()
+
+#define CREATE_TEST_DRAW_REVERSE_POLYGON(name, points_vector, id)         \
+  DrawPolygon name(NULL, points_vector, gfx::Vector3dF(0, 0, -1.0f), id); \
   name.RecomputeNormalForTesting()
 
 #define EXPECT_FLOAT_WITHIN_EPSILON_OF(a, b) \
   EXPECT_TRUE(std::abs(a - b) < std::numeric_limits<float>::epsilon());
 
 #define EXPECT_POINT_EQ(point_a, point_b)    \
   EXPECT_FLOAT_EQ(point_a.x(), point_b.x()); \
   EXPECT_FLOAT_EQ(point_a.y(), point_b.y()); \
   EXPECT_FLOAT_EQ(point_a.z(), point_b.z());
 
@@ skipping 18 matching lines @@
 }
 
 // More complicated shapes.
 TEST(DrawPolygonConstructionTest, TestNormal) {
   std::vector<gfx::Point3F> vertices;
   vertices.push_back(gfx::Point3F(0.0f, 10.0f, 0.0f));
   vertices.push_back(gfx::Point3F(0.0f, 0.0f, 0.0f));
   vertices.push_back(gfx::Point3F(10.0f, 0.0f, 0.0f));
   vertices.push_back(gfx::Point3F(10.0f, 10.0f, 0.0f));
 
-  CREATE_TEST_DRAW_POLYGON(polygon, vertices, 1);
+  CREATE_TEST_DRAW_FORWARD_POLYGON(polygon, vertices, 1);
   EXPECT_NORMAL(polygon, 0.0f, 0.0f, 1.0f);
 }
 
 TEST(DrawPolygonConstructionTest, ClippedNormal) {
   std::vector<gfx::Point3F> vertices;
   vertices.push_back(gfx::Point3F(0.1f, 10.0f, 0.0f));
   vertices.push_back(gfx::Point3F(0.0f, 9.9f, 0.0f));
   vertices.push_back(gfx::Point3F(0.0f, 10.0f, 0.0f));
   vertices.push_back(gfx::Point3F(0.0f, 0.0f, 0.0f));
   vertices.push_back(gfx::Point3F(10.0f, 0.0f, 0.0f));
   vertices.push_back(gfx::Point3F(10.0f, 10.0f, 0.0f));
 
-  CREATE_TEST_DRAW_POLYGON(polygon, vertices, 1);
+  CREATE_TEST_DRAW_FORWARD_POLYGON(polygon, vertices, 1);
   EXPECT_NORMAL(polygon, 0.0f, 0.0f, 1.0f);
 }
 
 TEST(DrawPolygonConstructionTest, SlimTriangleNormal) {
   std::vector<gfx::Point3F> vertices;
   vertices.push_back(gfx::Point3F(0.0f, 0.0f, 0.0f));
   vertices.push_back(gfx::Point3F(5000.0f, 0.0f, 0.0f));
   vertices.push_back(gfx::Point3F(10000.0f, 1.0f, 0.0f));
 
-  CREATE_TEST_DRAW_POLYGON(polygon, vertices, 2);
+  CREATE_TEST_DRAW_FORWARD_POLYGON(polygon, vertices, 2);
   EXPECT_NORMAL(polygon, 0.0f, 0.0f, 1.0f);
 }
 
 TEST(DrawPolygonConstructionTest, ManyVertexNormal) {
   std::vector<gfx::Point3F> vertices_c;
   std::vector<gfx::Point3F> vertices_d;
   for (int i = 0; i < 100; i++) {
     vertices_c.push_back(
         gfx::Point3F(cos(i * M_PI / 50), sin(i * M_PI / 50), 0.0f));
     vertices_d.push_back(gfx::Point3F(cos(i * M_PI / 50) + 99.0f,
                                       sin(i * M_PI / 50) + 99.0f, 100.0f));
   }
-  CREATE_TEST_DRAW_POLYGON(polygon_c, vertices_c, 3);
+  CREATE_TEST_DRAW_FORWARD_POLYGON(polygon_c, vertices_c, 3);
   EXPECT_NORMAL(polygon_c, 0.0f, 0.0f, 1.0f);
 
-  CREATE_TEST_DRAW_POLYGON(polygon_d, vertices_d, 4);
+  CREATE_TEST_DRAW_FORWARD_POLYGON(polygon_d, vertices_d, 4);
   EXPECT_NORMAL(polygon_c, 0.0f, 0.0f, 1.0f);
 }
 
 // A simple rect being transformed.
 TEST(DrawPolygonConstructionTest, SimpleNormal) {
   gfx::RectF src(-0.1f, -10.0f, 0.2f, 20.0f);
 
   gfx::Transform transform_i(1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1);
   DrawPolygon polygon_i(NULL, src, transform_i, 1);
 
@@ skipping 29 matching lines @@
 
 TEST(DrawPolygonConstructionTest, NormalRotate90) {
   gfx::RectF src(-0.1f, -10.0f, 0.2f, 20.0f);
 
   gfx::Transform transform(0, -1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1);
   DrawPolygon polygon_b(NULL, src, transform, 3);
 
   EXPECT_NORMAL(polygon_b, 0.0f, 0.0f, 1.0f);
 }
 
-// Bug https://bugs.chromium.org/p/chromium/issues/detail?id=595820
-TEST(DrawPolygonConstructionTest, DISABLED_InvertXNormal) {
+TEST(DrawPolygonConstructionTest, InvertXNormal) {
   gfx::RectF src(-0.1f, -10.0f, 0.2f, 20.0f);
 
   gfx::Transform transform(-1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1);
   DrawPolygon polygon_d(NULL, src, transform, 5);
 
   EXPECT_NORMAL(polygon_d, 0.0f, 0.0f, 1.0f);
 }
 
-TEST(DrawPolygonConstructionTest, DISABLED_InvertYNormal) {
+TEST(DrawPolygonConstructionTest, InvertYNormal) {
   gfx::RectF src(-0.1f, -10.0f, 0.2f, 20.0f);
 
   gfx::Transform transform(1, 0, 0, 0, 0, -1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1);
   DrawPolygon polygon_d(NULL, src, transform, 5);
 
   EXPECT_NORMAL(polygon_d, 0.0f, 0.0f, 1.0f);
 }
 
-TEST(DrawPolygonConstructionTest, DISABLED_InvertZNormal) {
+TEST(DrawPolygonConstructionTest, InvertZNormal) {
   gfx::RectF src(-0.1f, -10.0f, 0.2f, 20.0f);
 
   gfx::Transform transform(1, 0, 0, 0, 0, 1, 0, 0, 0, 0, -1, 0, 0, 0, 0, 1);
   DrawPolygon polygon_d(NULL, src, transform, 5);
 
   EXPECT_NORMAL(polygon_d, 0.0f, 0.0f, -1.0f);
 }
 
 // Two quads are nearly touching but definitely ordered. Second one should
 // compare in front.
@@ skipping 171 matching lines @@
 
   ValidatePoints(*(front_polygon.get()), test_points_a);
   ValidatePoints(*(back_polygon.get()), test_points_b);
 }
 
 TEST(DrawPolygonTransformTest, TransformNormal) {
   std::vector<gfx::Point3F> vertices_a;
   vertices_a.push_back(gfx::Point3F(1.0f, 0.0f, 1.0f));
   vertices_a.push_back(gfx::Point3F(-1.0f, 0.0f, -1.0f));
   vertices_a.push_back(gfx::Point3F(0.0f, 1.0f, 0.0f));
-  CREATE_NEW_DRAW_POLYGON(
-      polygon_a, vertices_a, gfx::Vector3dF(0.707107f, 0.0f, -0.707107f), 0);
-  // Check we believe your little white lie.
-  EXPECT_NORMAL(polygon_a, 0.707107f, 0.0f, -0.707107f);
-
-  polygon_a.RecomputeNormalForTesting();
-  // Check that we recompute it more accurately.
+  CREATE_NEW_DRAW_POLYGON(polygon_a, vertices_a,
+                          gfx::Vector3dF(sqrt(2) / 2, 0.0f, -sqrt(2) / 2), 0);
   EXPECT_NORMAL(polygon_a, sqrt(2) / 2, 0.0f, -sqrt(2) / 2);
 
   gfx::Transform transform;
   transform.RotateAboutYAxis(45.0f);
   // This would transform the vertices as well, but we are transforming a
   // DrawPolygon with 0 vertices just to make sure our normal transformation
   // using the inverse tranpose matrix gives us the right result.
   polygon_a.TransformToScreenSpace(transform);
 
   // Note: We use EXPECT_FLOAT_WITHIN_EPSILON instead of EXPECT_FLOAT_EQUAL here
   // because some architectures (e.g., Arm64) employ a fused multiply-add
   // instruction which causes rounding asymmetry and reduces precision.
   // http://crbug.com/401117.
   EXPECT_NORMAL(polygon_a, 0.0f, 0.0f, -1.0f);
 }
 
 }  // namespace
 }  // namespace cc