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, 210 insertions, 0 deletions

diff --git a/source/blender/freestyle/intern/view_map/BoxGrid.cpp b/source/blender/freestyle/intern/view_map/BoxGrid.cpp
new file mode 100644
index 00000000000..757cf7b6559
--- /dev/null
+++ b/source/blender/freestyle/intern/view_map/BoxGrid.cpp
@@ -0,0 +1,210 @@
+//
+//  Filename         : BoxGrid.cpp
+//  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.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "BoxGrid.h"
+
+#include <stdexcept>
+#include <algorithm>
+
+using namespace std;
+
+// Helper Classes
+
+// OccluderData
+///////////////
+
+// Cell
+/////////
+
+BoxGrid::Cell::Cell () {}
+
+BoxGrid::Cell::~Cell () {}
+
+void BoxGrid::Cell::setDimensions(real x, real y, real sizeX, real sizeY) {
+	const real epsilon = 1.0e-06;
+	boundary[0] = x - epsilon;
+	boundary[1] = x + sizeX + epsilon;
+	boundary[2] = y - epsilon;
+	boundary[3] = y + sizeY + epsilon;
+}
+
+bool BoxGrid::Cell::compareOccludersByShallowestPoint (const BoxGrid::OccluderData* a, const BoxGrid::OccluderData* b) {
+	return a->shallowest < b->shallowest;
+}
+
+void BoxGrid::Cell::indexPolygons() {
+	// Sort occluders by their shallowest points.
+	sort(faces.begin(), faces.end(), compareOccludersByShallowestPoint);
+}
+
+// Iterator
+//////////////////
+
+BoxGrid::Iterator::Iterator (BoxGrid& grid, Vec3r& center, real epsilon) 
+	: _target(grid.transform(center)), 
+	_foundOccludee(false)
+{
+	// Find target cell
+	_cell = grid.findCell(_target);
+	#if boxgridlogging == 1
+		cout << "Searching for occluders of edge centered at " << _target << " in cell [" 
+			<< _cell->boundary[0] << ", " << _cell->boundary[1] << ", " << _cell->boundary[2] 
+			<< ", " << _cell->boundary[3] << "] (" << _cell->faces.size() << " occluders)" << endl;
+	#endif
+
+	// Set iterator
+	_current = _cell->faces.begin();
+}
+
+BoxGrid::Iterator::~Iterator () {}
+
+// BoxGrid
+/////////////////
+
+BoxGrid::BoxGrid(OccluderSource& source, GridDensityProvider& density, ViewMap *viewMap, Vec3r& viewpoint, bool enableQI)
+	: _viewpoint(viewpoint),
+	_enableQI(enableQI)
+{
+	cout << "Generate Cell structure" << endl;
+	// Generate Cell structure
+	assignCells(source, density, viewMap);
+	cout << "Distribute occluders" << endl;
+	// Fill Cells
+	distributePolygons(source);
+	cout << "Reorganize cells" << endl;
+	// Reorganize Cells
+	reorganizeCells();
+	cout << "Ready to use BoxGrid" << endl;
+}
+
+BoxGrid::~BoxGrid () {
+}
+
+void BoxGrid::assignCells (OccluderSource& source, GridDensityProvider& density, ViewMap *viewMap) {
+	_cellSize = density.cellSize();
+	_cellsX = density.cellsX();
+	_cellsY = density.cellsY();
+	_cellOrigin[0] = density.cellOrigin(0);
+	_cellOrigin[1] = density.cellOrigin(1);
+
+	// Now allocate the cell table and fill it with default (empty) cells
+	_cells.resize(_cellsX * _cellsY);
+	for ( cellContainer::iterator i = _cells.begin(), end = _cells.end(); i != end; ++i ) {
+		(*i) = NULL;
+	}
+
+	// Identify cells that will be used, and set the dimensions for each
+	ViewMap::fedges_container& fedges = viewMap->FEdges();
+	for (ViewMap::fedges_container::iterator f = fedges.begin(), fend = fedges.end(); f != fend; ++f ) {
+		if ( (*f)->isInImage() ) {
+			Vec3r point = transform((*f)->center3d());
+			unsigned i, j;
+			getCellCoordinates(point, i, j);
+			if ( _cells[i * _cellsY + j] == NULL ) {
+				// This is an uninitialized cell
+
+				real x, y, width, height;
+
+				x = _cellOrigin[0] + _cellSize * i;
+				width = _cellSize;
+
+				y = _cellOrigin[1] + _cellSize * j;
+				height = _cellSize;
+
+				// Initialize cell
+				Cell* b = _cells[i * _cellsY + j] = new Cell();
+				b->setDimensions(x, y, width, height);
+			}
+		}
+	}
+}
+
+void BoxGrid::distributePolygons (OccluderSource& source) {
+	unsigned long nFaces = 0;
+	unsigned long nKeptFaces = 0;
+
+	for ( source.begin(); source.isValid(); source.next() ) {
+		OccluderData* occluder = NULL;
+
+		try {
+			if ( insertOccluder(source, occluder) ) {
+				_faces.push_back(occluder);
+				++nKeptFaces;
+			}
+		} catch (...) {
+			// If an exception was thrown, _faces.push_back() cannot have succeeded.
+			// occluder is not owned by anyone, and must be deleted.
+			// If the exception was thrown before or during new OccluderData(), then
+			// occluder is NULL, and this delete is harmless.
+			delete occluder;
+			throw;
+		}
+		++nFaces;
+	}
+	cout << "Distributed " << nFaces << " occluders.  Retained " << nKeptFaces << "." << endl;
+}
+
+void BoxGrid::reorganizeCells () {
+	// Sort the occluders by shallowest point
+	for ( vector<Cell*>::iterator i = _cells.begin(), end = _cells.end(); i != end; ++i ) {
+		if ( *i != NULL ) {
+			(*i)->indexPolygons();
+		}
+	}
+}
+
+void BoxGrid::getCellCoordinates(const Vec3r& point, unsigned& x, unsigned& y) {
+	x = min(_cellsX - 1, (unsigned) floor (max((double) 0.0f, point[0] - _cellOrigin[0]) / _cellSize));
+	y = min(_cellsY - 1, (unsigned) floor (max((double) 0.0f, point[1] - _cellOrigin[1]) / _cellSize));
+}
+
+BoxGrid::Cell* BoxGrid::findCell(const Vec3r& point) {
+	unsigned x, y;
+	getCellCoordinates(point, x, y);
+	return _cells[x * _cellsY + y];
+}
+
+bool BoxGrid::orthographicProjection () const {
+	return true;
+}
+
+const Vec3r& BoxGrid::viewpoint() const {
+	return _viewpoint;
+}
+
+bool BoxGrid::enableQI() const {
+	return _enableQI;
+}
+
+BoxGrid::Transform::Transform () : GridHelpers::Transform() {}
+
+Vec3r BoxGrid::Transform::operator() (const Vec3r& point) const {
+	return Vec3r(point[0], point[1], -point[2]);
+}
+