Optimized view map calculation by Alexander Beels.

* View map calculation has been intensively optimized for speed by
means of:

1) new spatial grid data structures (SphericalGrid for perspective
cameras and BoxGrid for orthographic cameras; automatically switched
based on the camera type);

2) a heuristic grid density calculation algorithm; and

3) new line visibility computation algorithms: A "traditional"
algorithm for emulating old visibility algorithms, and a "cumulative"
algorithm for improved, more consistent line visibility, both exploiting
the new spatial grid data structures for fast ray casting.

A new option "Raycasting Algorithm" was added to allow users to choose
a ray casting (line visibility) algorithm.  Available choices are:

- Normal Ray Casting
- Fast Ray Casting
- Very Fast Ray Casting
- Culled Traditional Visibility Detection
- Unculled Traditional Visibility Detection
- Culled Cumulative Visibility Detection
- Unculled Cumulative Visibility Detection

The first three algorithms are those available in the original
Freestyle (the "normal" ray casting was used unconditionally, though).
The "fast" and "very fast" ray casting algorithms achieve a faster
calculation at the cost of less visibility accuracy.

The last four are newly introduced optimized options.  The culled
versions of the new algorithms will exclude from visibility
calculation those faces that lay outside the camera, which leads to a
faster view map construction.  The unculled counterparts will take all
faces into account.  The unculled visibility algorithms are useful
when culling affects stroke chaining.

The recommended options for users are the culled/unculled cumulative
visibility algorithms.  These options are meant to replace the old
algorithms in the future.

Performance improvements over the old algorithms depend on the scenes
to be rendered.

* Silhouette detection has also been considerably optimized for speed.

Performance gains by this optimization do not depend on scenes.

* Improper handling of error conditions in the view map construction
was fixed.

1 files changed, 376 insertions, 0 deletions

diff --git a/source/blender/freestyle/intern/view_map/BoxGrid.h b/source/blender/freestyle/intern/view_map/BoxGrid.h
new file mode 100644
index 00000000000..43de8d713d5
--- /dev/null
+++ b/source/blender/freestyle/intern/view_map/BoxGrid.h
@@ -0,0 +1,376 @@
+//
+//  Filename         : BoxGrid.h
+//  Author(s)        : Alexander Beels
+//  Purpose          : Class to define a cell grid surrounding
+//                     the projected image of a scene
+//  Date of creation : 2011-1-29
+//
+///////////////////////////////////////////////////////////////////////////////
+
+
+//
+//  Copyright (C) : Please refer to the COPYRIGHT file distributed 
+//   with this source distribution. 
+//
+//  This program is free software; you can redistribute it and/or
+//  modify it under the terms of the GNU General Public License
+//  as published by the Free Software Foundation; either version 2
+//  of the License, or (at your option) any later version.
+//
+//  This program is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU General Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License
+//  along with this program; if not, write to the Free Software
+//  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef BOXGRID_H
+#define BOXGRID_H
+
+#define boxgridlogging 0
+
+// I would like to avoid using deque because including ViewMap.h and <deque> or <vector>
+// separately results in redefinitions of identifiers.  ViewMap.h already includes <vector> 
+// so it should be a safe fall-back.
+//#include <vector>
+//#include <deque>
+#include "ViewMap.h"
+#include "../winged_edge/WEdge.h"
+#include "../geometry/Polygon.h"
+#include "../system/PointerSequence.h"
+#include "../geometry/BBox.h"
+#include "../geometry/GridHelpers.h"
+#include "OccluderSource.h"
+#include "GridDensityProvider.h"
+
+class BoxGrid
+{
+public:
+	// Helper classes
+	struct OccluderData {
+		explicit OccluderData (OccluderSource& source, Polygon3r& p);
+		Polygon3r poly;
+		Polygon3r cameraSpacePolygon;
+		real shallowest, deepest;
+		// N.B. We could, of course, store face in poly's userdata
+		// member, like the old ViewMapBuilder code does.  However,
+		// code comments make it clear that userdata is deprecated,
+		// so we avoid the temptation to save 4 or 8 bytes.
+		WFace* face;
+	};
+
+private:
+	struct Cell {
+		// Can't store Cell in a vector without copy and assign
+		//Cell(const Cell& other);
+		//Cell& operator= (const Cell& other);
+
+		explicit Cell ();
+		~Cell ();
+
+		static bool compareOccludersByShallowestPoint (const OccluderData* a, const OccluderData* b);
+
+		void setDimensions(real x, real y, real sizeX, real sizeY);
+		void checkAndInsert(OccluderSource& source, Polygon3r& poly, OccluderData*& occluder);
+		void indexPolygons();
+
+		real boundary[4];
+		//deque<OccluderData*> faces;
+		vector<OccluderData*> faces;
+	};
+
+public:
+	/*****
+
+	Iterator needs to allow the user to avoid full 3D comparison in
+	two cases:
+
+	(1) Where (*current)->deepest < target[2], where the occluder is 
+	unambiguously in front of the target point.
+
+	(2) Where (*current)->shallowest > target[2], where the occluder
+	is unambiguously in back of the target point.
+
+	In addition, when used by OptimizedFindOccludee, Iterator should
+	stop iterating as soon as it has an occludee candidate and 
+	(*current)->shallowest > candidate[2], because at that point forward
+	no new occluder could possibly be a better occludee.
+
+	*****/
+
+	class Iterator {
+	public:
+		// epsilon is not used in this class, but other grids with the same interface may need an epsilon
+		explicit Iterator (BoxGrid& grid, Vec3r& center, real epsilon=1e-06);
+		~Iterator ();
+		void initBeforeTarget ();
+		void initAfterTarget ();
+		void nextOccluder ();
+		void nextOccludee ();
+		bool validBeforeTarget();
+		bool validAfterTarget();
+		WFace* getWFace() const;
+		Polygon3r* getCameraSpacePolygon();
+		void reportDepth(Vec3r origin, Vec3r u, real t);
+	private:
+		bool testOccluder(bool wantOccludee);
+		void markCurrentOccludeeCandidate(real depth);
+
+		Cell* _cell;
+		Vec3r _target;
+		bool _foundOccludee;
+		real _occludeeDepth;
+		//deque<OccluderData*>::iterator _current, _occludeeCandidate;
+		vector<OccluderData*>::iterator _current, _occludeeCandidate;
+	};
+
+	class Transform : public GridHelpers::Transform {
+	public:
+		explicit Transform ();
+		explicit Transform (Transform& other);
+		Vec3r operator() (const Vec3r& point) const;
+	};
+
+private:
+	// Prevent implicit copies and assignments.
+	BoxGrid(const BoxGrid& other);
+	BoxGrid& operator= (const BoxGrid& other);
+public:
+	explicit BoxGrid (OccluderSource& source, GridDensityProvider& density, ViewMap *viewMap, Vec3r& viewpoint, bool enableQI);
+	virtual ~BoxGrid();
+
+	// Generate Cell structure
+	void assignCells(OccluderSource& source, GridDensityProvider& density, ViewMap *viewMap);
+	// Fill Cells
+	void distributePolygons(OccluderSource& source);
+	// Insert one polygon into each matching cell, 
+	// return true if any cell consumes the polygon
+	bool insertOccluder(OccluderSource& source, OccluderData*& occluder);
+	// Sort occluders in each cell
+	void reorganizeCells();
+
+	Cell* findCell(const Vec3r& point);
+
+	// Accessors:
+	bool orthographicProjection() const;
+	const Vec3r& viewpoint() const;
+	bool enableQI() const; 
+	Transform transform;
+
+private:
+	void getCellCoordinates(const Vec3r& point, unsigned& x, unsigned& y);
+
+	typedef PointerSequence<vector<Cell*>, Cell*> cellContainer;
+	//typedef PointerSequence<deque<OccluderData*>, OccluderData*> occluderContainer;
+	typedef PointerSequence<vector<OccluderData*>, OccluderData*> occluderContainer;
+	unsigned _cellsX, _cellsY;
+	float _cellSize;
+	float _cellOrigin[2];
+	cellContainer _cells;
+	occluderContainer _faces;
+	Vec3r _viewpoint;
+	bool _enableQI;
+};
+
+inline void BoxGrid::Iterator::initBeforeTarget () {
+	_current = _cell->faces.begin();
+	while ( _current != _cell->faces.end() && ! testOccluder(false) ) {
+		++_current;
+	}
+}
+
+inline void BoxGrid::Iterator::initAfterTarget () {
+	if ( _foundOccludee ) {
+		#if boxgridlogging == 1
+			std::cout << "\tStarting occludee search from occludeeCandidate at depth " << _occludeeDepth << std::endl;
+		#endif
+		_current = _occludeeCandidate;
+		return;
+	}
+
+	#if boxgridlogging == 1
+		std::cout << "\tStarting occludee search from current position" << std::endl;
+	#endif
+
+	while ( _current != _cell->faces.end() && ! testOccluder(true) ) {
+		++_current;
+	}
+}
+
+inline bool BoxGrid::Iterator::testOccluder (bool wantOccludee) {
+	// End-of-list is not even a valid iterator position
+	if ( _current == _cell->faces.end() ) {
+		// Returning true seems strange, but it will break us out of whatever loop
+		// is calling testOccluder, and _current=_cell->face.end() will make
+		// the calling routine give up.
+		return true;
+	}
+	#if boxgridlogging == 1
+		std::cout << "\tTesting occluder " << (*_current)->poly.getVertices()[0];
+		for ( unsigned i = 1; i < (*_current)->poly.getVertices().size(); ++i ) {
+			std::cout << ", " << (*_current)->poly.getVertices()[i];
+		}
+		std::cout << " from shape " << (*_current)->face->GetVertex(0)->shape()->GetId() << std::endl;
+	#endif
+
+
+	// If we have an occluder candidate and we are unambiguously after it, abort
+	if ( _foundOccludee && (*_current)->shallowest > _occludeeDepth ) {
+		#if boxgridlogging == 1
+			std::cout << "\t\tAborting: shallowest > occludeeCandidate->deepest" << std::endl;
+		#endif
+		_current = _cell->faces.end();
+
+		// See note above
+		return true;
+	}
+
+	// Specific continue or stop conditions when searching for each type
+	if ( wantOccludee ) {
+		if ( (*_current)->deepest < _target[2] ) {
+			#if boxgridlogging == 1
+				std::cout << "\t\tSkipping: shallower than target while looking for occludee" << std::endl;
+			#endif
+			return false;
+		}
+	} else {
+		if ( (*_current)->shallowest > _target[2] ) {
+			#if boxgridlogging == 1
+				std::cout << "\t\tStopping: deeper than target while looking for occluder" << std::endl;
+			#endif
+			return true;
+		}
+	}
+
+	// Depthwise, this is a valid occluder.
+
+	// Check to see if target is in the 2D bounding box
+	Vec3r bbMin, bbMax;
+	(*_current)->poly.getBBox(bbMin, bbMax);
+	if ( _target[0] < bbMin[0] || _target[0] > bbMax[0] || _target[1] < bbMin[1] || _target[1] > bbMax[1] ) {
+		#if boxgridlogging == 1
+			std::cout << "\t\tSkipping: bounding box violation" << std::endl;
+		#endif
+		return false;
+	}
+
+	// We've done all the corner cutting we can.
+	// Let the caller work out whether or not
+	// the geometry is correct.
+	return true;
+}
+
+inline void BoxGrid::Iterator::reportDepth (Vec3r origin, Vec3r u, real t) {
+	// The reported depth is the length of a ray in camera space
+	// We need to convert it into a Z-value in grid space
+	real depth = -(origin + (u * t))[2];
+	#if boxgridlogging == 1
+		std::cout << "\t\tReporting depth of occluder/ee: " << depth;
+	#endif
+	if ( depth > _target[2] ) {
+		#if boxgridlogging == 1
+			std::cout << " is deeper than target" << std::endl;
+		#endif
+		// If the current occluder is the best occludee so far, save it.
+		if ( ! _foundOccludee || _occludeeDepth > depth ) {
+			markCurrentOccludeeCandidate(depth);
+		} 
+	} else {
+		#if boxgridlogging == 1
+			std::cout << std::endl;
+		#endif
+	}
+}
+
+inline void BoxGrid::Iterator::nextOccluder () {
+	if ( _current != _cell->faces.end() ) {
+		do {
+			++_current;
+		} while ( _current != _cell->faces.end() && ! testOccluder(false) );
+	}
+}
+
+inline void BoxGrid::Iterator::nextOccludee () {
+	if ( _current != _cell->faces.end() ) {
+		do {
+			++_current;
+		} while ( _current != _cell->faces.end() && ! testOccluder(true) );
+	}
+}
+
+inline bool BoxGrid::Iterator::validBeforeTarget () {
+	return _current != _cell->faces.end() && (*_current)->shallowest <= _target[2];
+}
+
+inline bool BoxGrid::Iterator::validAfterTarget () {
+	return _current != _cell->faces.end();
+}
+
+inline void BoxGrid::Iterator::markCurrentOccludeeCandidate(real depth) {
+	#if boxgridlogging == 1
+		std::cout << "\t\tFound occludeeCandidate at depth " << depth << std::endl;
+	#endif
+	_occludeeCandidate = _current;
+	_occludeeDepth = depth;
+	_foundOccludee = true;
+}
+
+inline WFace* BoxGrid::Iterator::getWFace() const {
+	return (*_current)->face;
+}
+
+inline Polygon3r* BoxGrid::Iterator::getCameraSpacePolygon() {
+	return &((*_current)->cameraSpacePolygon);
+}
+
+inline BoxGrid::OccluderData::OccluderData (OccluderSource& source, Polygon3r& p)
+	: poly(p), 
+	cameraSpacePolygon(source.getCameraSpacePolygon()),
+	face(source.getWFace())
+{
+	// Set shallowest and deepest based on bbox
+	Vec3r min, max;
+	poly.getBBox(min, max);
+	shallowest = min[2];
+	deepest = max[2];
+}
+
+inline void BoxGrid::Cell::checkAndInsert(OccluderSource& source, Polygon3r& poly, OccluderData*& occluder) {
+	if ( GridHelpers::insideProscenium (boundary, poly) ) {
+		if ( occluder == NULL) {
+			// Disposal of occluder will be handled in BoxGrid::distributePolygons(),
+			// or automatically by BoxGrid::_faces;
+			occluder = new OccluderData(source, poly);
+		}
+		faces.push_back(occluder);
+	}
+}
+
+inline bool BoxGrid::insertOccluder(OccluderSource& source, OccluderData*& occluder) {
+	Polygon3r& poly(source.getGridSpacePolygon());
+	occluder = NULL;
+
+	Vec3r bbMin, bbMax;
+	poly.getBBox(bbMin, bbMax);
+	// Check overlapping cells
+	unsigned startX, startY, endX, endY;
+	getCellCoordinates(bbMin, startX, startY);
+	getCellCoordinates(bbMax, endX, endY);
+
+	for ( unsigned i = startX; i <= endX; ++i ) {
+		for ( unsigned j = startY; j <= endY; ++j ) {
+			if ( _cells[i * _cellsY + j] != NULL ) {
+				_cells[i * _cellsY + j]->checkAndInsert(source, poly, occluder);
+			}
+		}
+	}
+
+	return occluder != NULL;
+}
+
+#endif // BOXGRID_H
+