Splitting of layers for correct intersections

cc/quads/draw_polygon.cc

Index: cc/quads/draw_polygon.cc
diff --git a/cc/quads/draw_polygon.cc b/cc/quads/draw_polygon.cc
index 026be2cb9d79fce319e956f397f0d1c15de637b3..6544b641acb237d07d6525015df5ae3abc93b369 100644
--- a/cc/quads/draw_polygon.cc
+++ b/cc/quads/draw_polygon.cc
@@ -12,7 +12,7 @@
 namespace {
 // This allows for some imperfection in the normal comparison when checking if
 // two pieces of geometry are coplanar.
-static const float coplanar_dot_epsilon = 0.01f;
+static const float coplanar_dot_epsilon = 0.001f;
 // This threshold controls how "thick" a plane is. If a point's distance is
 // <= |compare_threshold|, then it is considered on the plane. Only when this
 // boundary is crossed do we consider doing splitting.
@@ -25,21 +25,23 @@ static const float compare_threshold = 1.0f;
 // points that SHOULD be intersecting the "thick plane", but actually fail to
 // test positively for it because |split_threshold| allowed them to be outside
 // this range.
+// This is really supposd to be compare_threshold / 2.0f, but that would
+// create another static initializer.
 static const float split_threshold = 0.5f;
+
+static const float normalized_threshold = 0.001f;
 }  // namespace
 
 namespace cc {
 
-gfx::Vector3dF DrawPolygon::default_normal = gfx::Vector3dF(0.0f, 0.0f, -1.0f);
-
 DrawPolygon::DrawPolygon() {
 }
 
-DrawPolygon::DrawPolygon(DrawQuad* original,
+DrawPolygon::DrawPolygon(const DrawQuad* original,
                          const std::vector<gfx::Point3F>& in_points,
                          const gfx::Vector3dF& normal,
                          int draw_order_index)
-    : order_index_(draw_order_index), original_ref_(original) {
+    : order_index_(draw_order_index), original_ref_(original), is_split_(true) {
   for (size_t i = 0; i < in_points.size(); i++) {
     points_.push_back(in_points[i]);
   }
@@ -49,12 +51,14 @@ DrawPolygon::DrawPolygon(DrawQuad* original,
 // This takes the original DrawQuad that this polygon should be based on,
 // a visible content rect to make the 4 corner points from, and a transformation
 // to move it and its normal into screen space.
-DrawPolygon::DrawPolygon(DrawQuad* original_ref,
+DrawPolygon::DrawPolygon(const DrawQuad* original_ref,
                          const gfx::RectF& visible_content_rect,
                          const gfx::Transform& transform,
                          int draw_order_index)
-    : order_index_(draw_order_index), original_ref_(original_ref) {
-  normal_ = default_normal;
+    : normal_(0.0f, 0.0f, 1.0f),

[Nico, 2015/03/12 02:50:46]

Alternatively, you could do

gfx::Vector3dF kDefaultNormal() { return gfx::Vector3dF(0, 0, 1); }

and then write normal_(kDefaultNormal()) here.

Then the constant is initialized when DrawPolygon objects are created, not on
program startup.


The stdout of the sizes step of the linux and mac bots print a list of static
intializers. You can compare that output to the previous build to see how much
you added. This definitely removes one of them, so if it was just one you should
be ok to reland.

+      order_index_(draw_order_index),
+      original_ref_(original_ref),
+      is_split_(false) {
   gfx::Point3F points[8];
   int num_vertices_in_clipped_quad;
   gfx::QuadF send_quad(visible_content_rect);
@@ -97,6 +101,9 @@ float DrawPolygon::SignedPointDistance(const gfx::Point3F& point) const {
 // Assumes that layers are split and there are no intersecting planes.
 BspCompareResult DrawPolygon::SideCompare(const DrawPolygon& a,
                                           const DrawPolygon& b) {
+  // Let's make sure that both of these are normalized.
+  DCHECK_GE(normalized_threshold, std::abs(a.normal_.LengthSquared() - 1.0f));
+  DCHECK_GE(normalized_threshold, std::abs(b.normal_.LengthSquared() - 1.0f));
   // Right away let's check if they're coplanar
   double dot = gfx::DotProduct(a.normal_, b.normal_);
   float sign = 0.0f;
@@ -105,7 +112,7 @@ BspCompareResult DrawPolygon::SideCompare(const DrawPolygon& a,
   if (std::abs(dot) >= 1.0f - coplanar_dot_epsilon) {
     normal_match = true;
     // The normals are matching enough that we only have to test one point.
-    sign = gfx::DotProduct(a.points_[0] - b.points_[0], b.normal_);
+    sign = b.SignedPointDistance(a.points_[0]);
     // Is it on either side of the splitter?
     if (sign < -compare_threshold) {
       return BSP_BACK;
@@ -168,7 +175,7 @@ static bool LineIntersectPlane(const gfx::Point3F& line_start,
 
   // The case where one vertex lies on the thick-plane and the other
   // is outside of it.
-  if (std::abs(start_distance) < distance_threshold &&
+  if (std::abs(start_distance) <= distance_threshold &&
       std::abs(end_distance) > distance_threshold) {
     intersection->SetPoint(line_start.x(), line_start.y(), line_start.z());
     return true;
@@ -270,7 +277,7 @@ bool DrawPolygon::Split(const DrawPolygon& splitter,
         break;
       }
     }
-    if (current_vertex++ > points_size) {
+    if (current_vertex++ > (points_size)) {
       break;
     }
   }
@@ -284,6 +291,7 @@ bool DrawPolygon::Split(const DrawPolygon& splitter,
 
   // First polygon.
   out_points[0].push_back(intersections[0]);
+  DCHECK_GE(vertex_before[1], start1);
   for (size_t i = start1; i <= vertex_before[1]; i++) {
     out_points[0].push_back(points_[i]);
     --points_remaining;
@@ -306,6 +314,9 @@ bool DrawPolygon::Split(const DrawPolygon& splitter,
   scoped_ptr<DrawPolygon> poly2(
       new DrawPolygon(original_ref_, out_points[1], normal_, order_index_));
 
+  DCHECK_GE(poly1->points().size(), 3u);
+  DCHECK_GE(poly2->points().size(), 3u);
+
   if (SideCompare(*poly1, splitter) == BSP_FRONT) {
     *front = poly1.Pass();
     *back = poly2.Pass();