From 4fc002747e8138501d08942be247e60cd99ac404 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 2 Jul 2016 18:34:13 +0300
Subject: [PATCH] Rework CompositeShape algorithms

The old version had problems with coplanar surfaces and sometimes failed
to produce intersections when it should have.
---
 source/geometry/compositeshape.h | 77 ++++++++++++++++++--------------
 source/geometry/intersection.h   |  6 +--
 source/geometry/union.h          |  6 +--
 3 files changed, 46 insertions(+), 43 deletions(-)

diff --git a/source/geometry/compositeshape.h b/source/geometry/compositeshape.h
index f0b1f52..0c2c838 100644
--- a/source/geometry/compositeshape.h
+++ b/source/geometry/compositeshape.h
@@ -21,7 +21,6 @@ protected:
 
 	ShapeArray shapes;
 	unsigned max_isect;
-	unsigned min_scratch;
 
 	CompositeShape() { }
 	CompositeShape(const Shape<T, D> &, const Shape<T, D> &);
@@ -66,20 +65,14 @@ template<typename T, unsigned D, typename O>
 inline void CompositeShape<T, D, O>::init()
 {
 	max_isect = 0;
-	min_scratch = 0;
 	for(typename ShapeArray::const_iterator i=shapes.begin(); i!=shapes.end(); ++i)
-	{
-		unsigned mi = (*i)->get_max_ray_intersections();
-		max_isect += mi;
-		min_scratch = std::max(min_scratch, mi);
-	}
+		max_isect += (*i)->get_max_ray_intersections();
 }
 
 template<typename T, unsigned D, typename O>
 inline CompositeShape<T, D, O>::CompositeShape(const CompositeShape<T, D, O> &other):
 	shapes(other.shapes),
-	max_isect(other.max_isect),
-	min_scratch(other.min_scratch)
+	max_isect(other.max_isect)
 {
 	for(typename ShapeArray::iterator i=shapes.begin(); i!=shapes.end(); ++i)
 		*i = (*i)->clone();
@@ -96,7 +89,6 @@ inline CompositeShape<T, D, O> &CompositeShape<T, D, O>::operator=(const Composi
 		*i = (*i)->clone();
 
 	max_isect = other.max_isect;
-	min_scratch = other.min_scratch;
 }
 
 template<typename T, unsigned D, typename O>
@@ -123,12 +115,12 @@ inline BoundingBox<T, D> CompositeShape<T, D, O>::get_axis_aligned_bounding_box(
 template<typename T, unsigned D, typename O>
 inline bool CompositeShape<T, D, O>::contains(const LinAl::Vector<T, D> &point) const
 {
-	bool inside = Ops::init_inside();
+	bool inside = false;
 	for(typename ShapeArray::const_iterator i=shapes.begin(); i!=shapes.end(); ++i)
 	{
-		inside = Ops::combine_inside(inside, (*i)->contains(point));
-		if(Ops::is_inside_decided(inside))
-			break;
+		inside = (*i)->contains(point);
+		if(Ops::shortcircuit(inside))
+			return inside;
 	}
 	return inside;
 }
@@ -138,39 +130,58 @@ inline unsigned CompositeShape<T, D, O>::get_intersections(const Ray<T, D> &ray,
 {
 	SurfacePoint<T, D> *buffer = points;
 	unsigned buf_size = size;
-	if(!points)
+	if(!points && !Ops::shortcircuit(true))
 	{
-		buffer = new SurfacePoint<T, D>[min_scratch];
-		buf_size = min_scratch;
+		buffer = new SurfacePoint<T, D>[max_isect];
+		buf_size = max_isect;
 	}
 
+	int start_nesting = 0;
 	unsigned n = 0;
-	for(typename ShapeArray::const_iterator i=shapes.begin(); (n<size && i!=shapes.end()); ++i)
+	for(typename ShapeArray::const_iterator i=shapes.begin(); (n<buf_size && i!=shapes.end()); ++i)
 	{
-		unsigned base = (points ? n : 0);
+		unsigned base = n;
 		unsigned count = (*i)->get_intersections(ray, buffer+base, buf_size-base);
-		for(unsigned j=0; (n<size && j<count); ++j)
+		bool start_inside = (*i)->contains(ray.get_start());
+
+		if(!count && !start_inside)
 		{
-			SurfacePoint<T, D> &pt = buffer[base+j];
+			if(Ops::shortcircuit(false))
+				return 0;
+			continue;
+		}
 
-			bool surface = Ops::init_surface();
-			for(typename ShapeArray::const_iterator k=shapes.begin(); k!=shapes.end(); ++k)
-				if(k!=i)
-					surface = Ops::combine_surface(surface, (*k)->contains(pt.position));
+		start_nesting += start_inside;
 
-			if(surface)
-			{
-				if(points && base+j!=n)
-					points[n] = pt;
+		if(!base)
+		{
+			n = count;
+			continue;
+		}
 
-				++n;
+		sort_points(buffer, base+count);
+
+		int nesting = start_nesting;
+		unsigned k = 0;
+		for(unsigned j=0; j<base+count; ++j)
+		{
+			if(Ops::shortcircuit(nesting+buffer[j].entry<2))
+			{
+				if(j!=k)
+					buffer[k] = buffer[j];
+				++k;
 			}
+
+			nesting += buffer[j].entry*2-1;
 		}
+
+		if(!k && Ops::shortcircuit(false))
+			return 0;
+
+		n = k;
 	}
 
-	if(points)
-		sort_points(points, n);
-	else
+	if(buffer!=points)
 		delete[] buffer;
 
 	return n;
diff --git a/source/geometry/intersection.h b/source/geometry/intersection.h
index 7d21f75..0e555b0 100644
--- a/source/geometry/intersection.h
+++ b/source/geometry/intersection.h
@@ -10,11 +10,7 @@ template<typename T, unsigned D>
 struct IntersectionOps
 {
 	static BoundingBox<T, D> combine_aabb(const BoundingBox<T, D> &a, const BoundingBox<T, D> &b) { return a&b; }
-	static bool init_inside() { return true; }
-	static bool combine_inside(bool a, bool b) { return a && b; }
-	static bool is_inside_decided(bool a) { return !a; }
-	static bool init_surface() { return true; }
-	static bool combine_surface(bool a, bool b) { return a && b; }
+	static bool shortcircuit(bool c) { return !c; }
 };
 
 /**
diff --git a/source/geometry/union.h b/source/geometry/union.h
index a1562cb..738f1f2 100644
--- a/source/geometry/union.h
+++ b/source/geometry/union.h
@@ -10,11 +10,7 @@ template<typename T, unsigned D>
 struct UnionOps
 {
 	static BoundingBox<T, D> combine_aabb(const BoundingBox<T, D> &a, const BoundingBox<T, D> &b) { return a|b; }
-	static bool init_inside() { return false; }
-	static bool combine_inside(bool a, bool b) { return a || b; }
-	static bool is_inside_decided(bool a) { return a; }
-	static bool init_surface() { return true; }
-	static bool combine_surface(bool a, bool b) { return a && !b; }
+	static bool shortcircuit(bool c) { return c; }
 };
 
 /**
-- 
2.45.2