From: Mikko Rasa <tdb@tdb.fi>
Date: Tue, 18 Apr 2017 11:16:45 +0000 (+0300)
Subject: Optimize bounding box bisection with more early culling
X-Git-Url: http://git.tdb.fi/?a=commitdiff_plain;h=2826730b5d68d1ad74dc6363af43ca796f96caa2;p=libs%2Fmath.git

Optimize bounding box bisection with more early culling
---

diff --git a/source/geometry/boundingbox.h b/source/geometry/boundingbox.h
index ac384ec..4ae2935 100644
--- a/source/geometry/boundingbox.h
+++ b/source/geometry/boundingbox.h
@@ -27,6 +27,9 @@ public:
 	T get_minimum_coordinate(unsigned i) const { return min_pt[i]; }
 	const LinAl::Vector<T, D> &get_maximum_point() const { return max_pt; }
 	T get_maximum_coordinate(unsigned i) const { return max_pt[i]; }
+	LinAl::Vector<T, D> get_dimensions() const { return max_pt-min_pt; }
+	T get_dimension(unsigned i) const { return max_pt[i]-min_pt[i]; }
+
 	bool is_empty() const { return empty && !negated; }
 	bool is_space() const { return empty && negated; }
 	bool is_negated() const { return negated; }
diff --git a/source/geometry/compositeshape.h b/source/geometry/compositeshape.h
index 5d0cd8c..c472b43 100644
--- a/source/geometry/compositeshape.h
+++ b/source/geometry/compositeshape.h
@@ -201,10 +201,12 @@ inline Coverage CompositeShape<T, D, O>::get_coverage(const BoundingBox<T, D> &b
 	for(typename ShapeArray::const_iterator i=shapes.begin(); i!=shapes.end(); ++i)
 	{
 		Coverage c = (*i)->get_coverage(bbox);
-		if(i==shapes.begin() || Ops::shortcircuit(c>coverage))
+		if(i==shapes.begin())
 			coverage = c;
+		else
+			coverage = Ops::combine_coverage(coverage, c);
 
-		if(coverage!=PARTIAL_COVERAGE && Ops::shortcircuit(coverage==FULL_COVERAGE))
+		if((coverage==NO_COVERAGE && Ops::shortcircuit(false)) || (coverage==FULL_COVERAGE && Ops::shortcircuit(true)))
 			break;
 	}
 
diff --git a/source/geometry/intersection.h b/source/geometry/intersection.h
index 0e555b0..24e668d 100644
--- a/source/geometry/intersection.h
+++ b/source/geometry/intersection.h
@@ -10,6 +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 Coverage combine_coverage(Coverage a, Coverage b) { return ((a==PARTIAL_COVERAGE && b==a) ? UNCERTAIN_COVERAGE : std::min(a, b)); }
 	static bool shortcircuit(bool c) { return !c; }
 };
 
diff --git a/source/geometry/negation.h b/source/geometry/negation.h
index 91802f8..60b92e3 100644
--- a/source/geometry/negation.h
+++ b/source/geometry/negation.h
@@ -96,7 +96,7 @@ inline Coverage Negation<T, D>::get_coverage(const BoundingBox<T, D> &bbox) cons
 	else if(coverage==NO_COVERAGE)
 		return FULL_COVERAGE;
 	else
-		return PARTIAL_COVERAGE;
+		return coverage;
 }
 
 } // namespace Geometry
diff --git a/source/geometry/shape.h b/source/geometry/shape.h
index 8eb3157..920e456 100644
--- a/source/geometry/shape.h
+++ b/source/geometry/shape.h
@@ -14,6 +14,7 @@ namespace Geometry {
 enum Coverage
 {
 	NO_COVERAGE,
+	UNCERTAIN_COVERAGE,
 	PARTIAL_COVERAGE,
 	FULL_COVERAGE
 };
@@ -96,6 +97,17 @@ inline BoundingBox<T, D> Shape<T, D>::bisect_axis_aligned_bounding_box(unsigned
 
 		const LinAl::Vector<T, D> &min_pt = cell.bounding_box.get_minimum_point();
 		const LinAl::Vector<T, D> &max_pt = cell.bounding_box.get_maximum_point();
+
+		// Skip cells that are already fully inside the established bounds.
+		bool internal = true;
+		for(unsigned i=0; (i<D && internal); ++i)
+			internal = (min_pt[i]>=tight_min_pt[i] && max_pt[i]<=tight_max_pt[i]);
+		if(internal)
+		{
+			queue.pop_front();
+			continue;
+		}
+
 		LinAl::Vector<T, D> center = (min_pt+max_pt)/T(2);
 
 		// Bisect each dimension.
@@ -118,9 +130,8 @@ inline BoundingBox<T, D> Shape<T, D>::bisect_axis_aligned_bounding_box(unsigned
 			child.coverage = get_coverage(child.bounding_box);
 			if(child.coverage==FULL_COVERAGE || (child.level==detail && child.coverage!=NO_COVERAGE))
 			{
-				/* Adjust the bounds when we are certain that it's covered by at
-				least part of the shape.  Also adjust for uncertain results if
-				we're on the last level. */
+				/* Immediately merge cells with full coverage.  Also merge cells
+				at the last level. */
 				for(unsigned j=0; j<D; ++j)
 				{
 					tight_min_pt[j] = std::min(tight_min_pt[j], child_min_pt[j]);
@@ -128,6 +139,17 @@ inline BoundingBox<T, D> Shape<T, D>::bisect_axis_aligned_bounding_box(unsigned
 				}
 			}
 			else if(child.coverage==PARTIAL_COVERAGE)
+			{
+				/* Merge cells with confirmed partial coverage so the cell is
+				left just outside the bounding box. */
+				for(unsigned j=0; j<D; ++j)
+				{
+					tight_min_pt[j] = std::min(tight_min_pt[j], child_max_pt[j]);
+					tight_max_pt[j] = std::max(tight_max_pt[j], child_min_pt[j]);
+				}
+			}
+
+			if(child.level<detail && child.coverage!=NO_COVERAGE && child.coverage!=FULL_COVERAGE)
 				queue.push_back(child);
 		}
 
diff --git a/source/geometry/transformedshape.h b/source/geometry/transformedshape.h
index 002f3c1..9387123 100644
--- a/source/geometry/transformedshape.h
+++ b/source/geometry/transformedshape.h
@@ -109,7 +109,30 @@ inline unsigned TransformedShape<T, D>::get_intersections(const Ray<T, D> &ray,
 template<typename T, unsigned D>
 inline Coverage TransformedShape<T, D>::get_coverage(const BoundingBox<T, D> &bbox) const
 {
-	return shape->get_coverage(inverse_trans.transform(bbox));
+	BoundingBox<T, D> local_bbox = inverse_trans.transform(bbox);
+	Coverage coverage = shape->get_coverage(local_bbox);
+	if(coverage==PARTIAL_COVERAGE)
+	{
+		BoundingBox<T, D> outer_bbox = transformation.transform(local_bbox);
+		LinAl::Vector<T, D> min_pt = local_bbox.get_minimum_point();
+		LinAl::Vector<T, D> max_pt = local_bbox.get_maximum_point();
+		for(unsigned i=0; i<D; ++i)
+		{
+			T scale_ratio = (1-bbox.get_dimension(i)/outer_bbox.get_dimension(i))*local_bbox.get_dimension(i);
+			T low_gap = bbox.get_minimum_coordinate(i)-outer_bbox.get_minimum_coordinate(i);
+			T high_gap = outer_bbox.get_maximum_coordinate(i)-bbox.get_maximum_coordinate(i);
+			min_pt[i] += low_gap*scale_ratio;
+			max_pt[i] -= high_gap-scale_ratio;
+		}
+
+		local_bbox = BoundingBox<T, D>(min_pt, max_pt);
+		if(shape->get_coverage(local_bbox)>=PARTIAL_COVERAGE)
+			return PARTIAL_COVERAGE;
+		else
+			return UNCERTAIN_COVERAGE;
+	}
+	else
+		return coverage;
 }
 
 } // namespace Geometry
diff --git a/source/geometry/union.h b/source/geometry/union.h
index 738f1f2..8c02f2b 100644
--- a/source/geometry/union.h
+++ b/source/geometry/union.h
@@ -10,6 +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 Coverage combine_coverage(Coverage a, Coverage b) { return std::max(a, b); }
 	static bool shortcircuit(bool c) { return c; }
 };