| // Copyright (c) 2012 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. |
| |
| #include "cobalt/math/quad_f.h" |
| |
| #include <limits> |
| |
| #include "base/strings/stringprintf.h" |
| |
| namespace cobalt { |
| namespace math { |
| |
| void QuadF::operator=(const RectF& rect) { |
| p1_ = PointF(rect.x(), rect.y()); |
| p2_ = PointF(rect.right(), rect.y()); |
| p3_ = PointF(rect.right(), rect.bottom()); |
| p4_ = PointF(rect.x(), rect.bottom()); |
| } |
| |
| std::string QuadF::ToString() const { |
| return base::StringPrintf("%s;%s;%s;%s", p1_.ToString().c_str(), |
| p2_.ToString().c_str(), p3_.ToString().c_str(), |
| p4_.ToString().c_str()); |
| } |
| |
| static inline bool WithinEpsilon(float a, float b) { |
| return std::abs(a - b) < std::numeric_limits<float>::epsilon(); |
| } |
| |
| bool QuadF::IsRectilinear() const { |
| return (WithinEpsilon(p1_.x(), p2_.x()) && WithinEpsilon(p2_.y(), p3_.y()) && |
| WithinEpsilon(p3_.x(), p4_.x()) && WithinEpsilon(p4_.y(), p1_.y())) || |
| (WithinEpsilon(p1_.y(), p2_.y()) && WithinEpsilon(p2_.x(), p3_.x()) && |
| WithinEpsilon(p3_.y(), p4_.y()) && WithinEpsilon(p4_.x(), p1_.x())); |
| } |
| |
| bool QuadF::IsCounterClockwise() const { |
| // This math computes the signed area of the quad. Positive area |
| // indicates the quad is clockwise; negative area indicates the quad is |
| // counter-clockwise. Note carefully: this is backwards from conventional |
| // math because our geometric space uses screen coordinates with y-axis |
| // pointing downwards. |
| // Reference: http://mathworld.wolfram.com/PolygonArea.html. |
| // The equation can be written: |
| // Signed area = determinant1 + determinant2 + determinant3 + determinant4 |
| // In practise, Refactoring the computation of adding determinants so that |
| // reducing the number of operations. The equation is: |
| // Signed area = element1 + element2 - element3 - element4 |
| |
| float p24 = p2_.y() - p4_.y(); |
| float p31 = p3_.y() - p1_.y(); |
| |
| // Up-cast to double so this cannot overflow. |
| double element1 = static_cast<double>(p1_.x()) * p24; |
| double element2 = static_cast<double>(p2_.x()) * p31; |
| double element3 = static_cast<double>(p3_.x()) * p24; |
| double element4 = static_cast<double>(p4_.x()) * p31; |
| |
| return element1 + element2 < element3 + element4; |
| } |
| |
| static inline bool PointIsInTriangle(const PointF& point, const PointF& r1, |
| const PointF& r2, const PointF& r3) { |
| // Translate point and triangle so that point lies at origin. |
| // Then checking if the origin is contained in the translated triangle. |
| // The origin O lies inside ABC if and only if the triangles OAB, OBC, |
| // and OCA are all either clockwise or counterclockwise. |
| // This algorithm is from Real-Time Collision Detection (Chapter 5.4.2). |
| |
| Vector2dF a = r1 - point; |
| Vector2dF b = r2 - point; |
| Vector2dF c = r3 - point; |
| |
| double u = CrossProduct(b, c); |
| double v = CrossProduct(c, a); |
| double w = CrossProduct(a, b); |
| return ((u * v < 0) || ((u * w) < 0) || ((v * w) < 0)) ? false : true; |
| } |
| |
| bool QuadF::Contains(const PointF& point) const { |
| return PointIsInTriangle(point, p1_, p2_, p3_) || |
| PointIsInTriangle(point, p1_, p3_, p4_); |
| } |
| |
| void QuadF::Scale(float x_scale, float y_scale) { |
| p1_.Scale(x_scale, y_scale); |
| p2_.Scale(x_scale, y_scale); |
| p3_.Scale(x_scale, y_scale); |
| p4_.Scale(x_scale, y_scale); |
| } |
| |
| void QuadF::operator+=(const Vector2dF& rhs) { |
| p1_ += rhs; |
| p2_ += rhs; |
| p3_ += rhs; |
| p4_ += rhs; |
| } |
| |
| void QuadF::operator-=(const Vector2dF& rhs) { |
| p1_ -= rhs; |
| p2_ -= rhs; |
| p3_ -= rhs; |
| p4_ -= rhs; |
| } |
| |
| QuadF operator+(const QuadF& lhs, const Vector2dF& rhs) { |
| QuadF result = lhs; |
| result += rhs; |
| return result; |
| } |
| |
| QuadF operator-(const QuadF& lhs, const Vector2dF& rhs) { |
| QuadF result = lhs; |
| result -= rhs; |
| return result; |
| } |
| |
| } // namespace math |
| } // namespace cobalt |