From cf11f7e8fbbe2c03a082c8b16dfddf761e050114 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20Vondru=C5=A1?= <mosra@centrum.cz>
Date: Mon, 23 Sep 2013 01:23:19 +0200
Subject: [PATCH] Shapes: (detailed) collision of sphere vs. point.

---
 src/Shapes/Sphere.cpp          | 23 ++++++++++++++++++++++-
 src/Shapes/Sphere.h            |  7 +++++++
 src/Shapes/Test/SphereTest.cpp | 29 +++++++++++++++++++++++------
 3 files changed, 52 insertions(+), 7 deletions(-)

diff --git a/src/Shapes/Sphere.cpp b/src/Shapes/Sphere.cpp
index 295a9ab0a..f07bcb247 100644
--- a/src/Shapes/Sphere.cpp
+++ b/src/Shapes/Sphere.cpp
@@ -41,7 +41,28 @@ template<UnsignedInt dimensions> Sphere<dimensions> Sphere<dimensions>::transfor
 }
 
 template<UnsignedInt dimensions> bool Sphere<dimensions>::operator%(const Point<dimensions>& other) const {
-    return (other.position()-_position).dot() < Math::pow<2>(_radius);
+    return (_position - other.position()).dot() < Math::pow<2>(_radius);
+}
+
+template<UnsignedInt dimensions> Collision<dimensions> Sphere<dimensions>::operator/(const Point<dimensions>& other) const {
+    const typename DimensionTraits<dimensions, Float>::VectorType separating = _position - other.position();
+    const Float dot = separating.dot();
+
+    /* No collision occured */
+    if(dot > Math::pow<2>(_radius)) return {};
+
+    /* Actual distance from the center */
+    const Float distance = Math::sqrt(dot);
+
+    /* Separating normal. If can't decide on direction, just move up. */
+    /** @todo How to handle this in a configurable way? */
+    const typename DimensionTraits<dimensions, Float>::VectorType separatingNormal =
+        Math::TypeTraits<Float>::equals(dot, 0.0f) ?
+        DimensionTraits<dimensions, Float>::VectorType::yAxis() :
+        separating/distance;
+
+    /* Collision position is on the point */
+    return Collision<dimensions>(other.position(), separatingNormal, _radius - distance);
 }
 
 template<UnsignedInt dimensions> bool Sphere<dimensions>::operator%(const Line<dimensions>& other) const {
diff --git a/src/Shapes/Sphere.h b/src/Shapes/Sphere.h
index e402f9c9e..6580efa8e 100644
--- a/src/Shapes/Sphere.h
+++ b/src/Shapes/Sphere.h
@@ -30,6 +30,7 @@
 
 #include "Math/Vector3.h"
 #include "DimensionTraits.h"
+#include "Shapes/Collision.h"
 #include "Shapes/Shapes.h"
 #include "Shapes/magnumShapesVisibility.h"
 
@@ -82,6 +83,9 @@ template<UnsignedInt dimensions> class MAGNUM_SHAPES_EXPORT Sphere {
         /** @brief %Collision occurence with point */
         bool operator%(const Point<dimensions>& other) const;
 
+        /** @brief %Collision with point */
+        Collision<dimensions> operator/(const Point<dimensions>& other) const;
+
         /** @brief %Collision occurence with line */
         bool operator%(const Line<dimensions>& other) const;
 
@@ -105,6 +109,9 @@ typedef Sphere<3> Sphere3D;
 /** @collisionoccurenceoperator{Point,Sphere} */
 template<UnsignedInt dimensions> inline bool operator%(const Point<dimensions>& a, const Sphere<dimensions>& b) { return b % a; }
 
+/** @collisionoperator{Point,Sphere} */
+template<UnsignedInt dimensions> inline Collision<dimensions> operator/(const Point<dimensions>& a, const Sphere<dimensions>& b) { return (b/a).flipped(); }
+
 /** @collisionoccurenceoperator{Line,Sphere} */
 template<UnsignedInt dimensions> inline bool operator%(const Line<dimensions>& a, const Sphere<dimensions>& b) { return b % a; }
 
diff --git a/src/Shapes/Test/SphereTest.cpp b/src/Shapes/Test/SphereTest.cpp
index b66e86e50..877176130 100644
--- a/src/Shapes/Test/SphereTest.cpp
+++ b/src/Shapes/Test/SphereTest.cpp
@@ -61,12 +61,29 @@ void SphereTest::transformed() {
 }
 
 void SphereTest::collisionPoint() {
-    Shapes::Sphere3D sphere({1.0f, 2.0f, 3.0f}, 2.0f);
-    Shapes::Point3D point({1.0f, 3.0f, 3.0f});
-    Shapes::Point3D point2({1.0f, 3.0f, 1.0f});
-
-    VERIFY_COLLIDES(sphere, point);
-    VERIFY_NOT_COLLIDES(sphere, point2);
+    const Shapes::Sphere3D sphere({1.0f, 2.0f, 3.0f}, 2.0f);
+
+    /* Collision */
+    const Shapes::Point3D point({2.5f, 2.0f, 3.0f});
+    const Shapes::Collision3D collision = sphere/point;
+    CORRADE_VERIFY(sphere%point && point%sphere);
+    CORRADE_COMPARE(collision.position(), point.position());
+    CORRADE_COMPARE(collision.separationNormal(), -Vector3::xAxis());
+    CORRADE_COMPARE(collision.separationDistance(), 0.5f);
+
+    /* Collision, flipped */
+    CORRADE_COMPARE(collision.separationNormal(), -(point/sphere).separationNormal());
+
+    /* Collision with ambiguous separation vector */
+    const Shapes::Point3D point2(sphere.position());
+    const Shapes::Collision3D collision2 = sphere/point2;
+    CORRADE_COMPARE(collision2.position(), point2.position());
+    CORRADE_COMPARE(collision2.separationNormal(), Vector3::yAxis());
+    CORRADE_COMPARE(collision2.separationDistance(), 2.0f);
+
+    /* No collision */
+    const Shapes::Point3D point3({-1.5f, 2.0f, 3.0f});
+    CORRADE_VERIFY(!(sphere%point3) && !(sphere/point3));
 }
 
 void SphereTest::collisionLine() {