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, 199 insertions, 0 deletions

diff --git a/source/blender/freestyle/intern/geometry/GridHelpers.h b/source/blender/freestyle/intern/geometry/GridHelpers.h
new file mode 100644
index 00000000000..b079005c1b5
--- /dev/null
+++ b/source/blender/freestyle/intern/geometry/GridHelpers.h
@@ -0,0 +1,199 @@
+//
+//  Filename         : GridHelpers.h
+//  Author(s)        : Alexander Beels
+//  Purpose          : Class to define a cell grid surrounding
+//                     the projected image of a scene
+//  Date of creation : 2010-12-13
+//
+///////////////////////////////////////////////////////////////////////////////
+
+
+//
+//  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  GRIDHELPERS_H
+#define GRIDHELPERS_H
+
+#include <vector>
+#include "Polygon.h"
+#include "../winged_edge/WEdge.h"
+#include "FRS_freestyle.h"
+#include "GeomUtils.h"
+
+namespace GridHelpers {
+
+/*! Computes the distance from a point P to a segment AB */
+template<class T>
+T closestPointToSegment(const T& P, const T& A , const T& B, real& distance) { 
+	T AB, AP, BP;
+	AB = B - A;
+	AP = P - A;
+	BP = P - B;
+
+	real c1(AB * AP);
+	if (c1 <= 0) {
+		distance = AP.norm();
+		return A; // A is closest point
+	}
+
+	real c2(AB * AB);
+	if (c2 <= c1) {
+		distance = BP.norm();
+		return B; // B is closest point
+	}
+
+    real b = c1 / c2;
+    T Pb, PPb;
+    Pb = A + b * AB;
+    PPb = P - Pb;
+
+    distance = PPb.norm();
+	return Pb; // closest point lies on AB
+} 
+
+inline Vec3r closestPointOnPolygon(const Vec3r& point, const Polygon3r& poly) {
+	// First cast a ray from the point onto the polygon plane
+	// If the ray intersects the polygon, then the intersection point
+	// is the closest point on the polygon
+	real t, u, v;
+	if ( poly.rayIntersect(point, poly.getNormal(), t, u, v) ) {
+		return point + poly.getNormal() * t;
+	}
+
+	// Otherwise, get the nearest point on each edge, and take the closest
+	real distance;
+	Vec3r closest = closestPointToSegment(point, poly.getVertices()[2], poly.getVertices()[0], distance);
+	for ( unsigned i = 0; i < 2; ++i ) {
+		real t;
+		Vec3r p = closestPointToSegment(point, poly.getVertices()[i], poly.getVertices()[i + 1], t);
+		if ( t < distance ) {
+			distance = t;
+			closest = p;
+		}
+	}
+	return closest;
+}
+
+inline real distancePointToPolygon(const Vec3r& point, const Polygon3r& poly) {
+	// First cast a ray from the point onto the polygon plane
+	// If the ray intersects the polygon, then the intersection point
+	// is the closest point on the polygon
+	real t, u, v;
+	if ( poly.rayIntersect(point, poly.getNormal(), t, u, v) ) {
+		return t > 0.0 ? t : -t;
+	}
+
+	// Otherwise, get the nearest point on each edge, and take the closest
+	real distance = GeomUtils::distPointSegment(point, poly.getVertices()[2], poly.getVertices()[0]);
+	for ( unsigned i = 0; i < 2; ++i ) {
+		real t = GeomUtils::distPointSegment(point, poly.getVertices()[i], poly.getVertices()[i + 1]);
+		if ( t < distance ) {
+			distance = t;
+		}
+	}
+	return distance;
+}
+
+class Transform {
+public:
+	virtual ~Transform () =0;
+	virtual Vec3r operator()(const Vec3r& point) const =0;
+};
+
+inline bool insideProscenium (const real proscenium[4], const Polygon3r& polygon) {
+	// N.B. The bounding box check is redundant for inserting occluders into
+	// cells, because the cell selection code in insertOccluders has already
+	// guaranteed that the bounding boxes will overlap.
+	// First check the viewport edges, since they are the easiest case
+	// Check if the bounding box is entirely outside the proscenium
+	Vec3r bbMin, bbMax;
+	polygon.getBBox(bbMin, bbMax);
+	if ( bbMax[0] < proscenium[0] 
+			|| bbMin[0] > proscenium[1] 
+			|| bbMax[1] < proscenium[2] 
+			|| bbMin[1] > proscenium[3] ) {
+		return false;
+	}
+
+	Vec3r boxCenter(proscenium[0] + (proscenium[1] - proscenium[0]) / 2.0, proscenium[2] + (proscenium[3] - proscenium[2]) / 2.0, 0.0);
+	Vec3r boxHalfSize((proscenium[1] - proscenium[0]) / 2.0, (proscenium[3] - proscenium[2]) / 2.0, 1.0);
+	Vec3r triverts[3] = { Vec3r(polygon.getVertices()[0][0], polygon.getVertices()[0][1], 0.0), Vec3r(polygon.getVertices()[1][0], polygon.getVertices()[1][1], 0.0), Vec3r(polygon.getVertices()[2][0], polygon.getVertices()[2][1], 0.0) };
+	return GeomUtils::overlapTriangleBox(boxCenter, boxHalfSize, triverts);
+}
+
+inline vector<Vec3r> enumerateVertices(const vector<WOEdge*>& fedges) {
+	vector<Vec3r> points;
+	// Iterate over vertices, storing projections in points
+	for(vector<WOEdge*>::const_iterator woe=fedges.begin(), woend=fedges.end(); woe!=woend; woe++) {
+		points.push_back((*woe)->GetaVertex()->GetVertex());
+	}
+
+	return points;
+}
+
+void getDefaultViewProscenium(real viewProscenium[4]);
+
+inline void expandProscenium (real proscenium[4], const Polygon3r& polygon) {
+	Vec3r bbMin, bbMax;
+	polygon.getBBox(bbMin, bbMax);
+
+	const real epsilon = 1.0e-6;
+
+	if ( bbMin[0] <= proscenium[0] ) {
+		proscenium[0] = bbMin[0] - epsilon;
+	}
+
+	if ( bbMin[1] <= proscenium[2] ) {
+		proscenium[2] = bbMin[1] - epsilon;
+	}
+
+	if ( bbMax[0] >= proscenium[1] ) {
+		proscenium[1] = bbMax[0] + epsilon;
+	}
+
+	if ( bbMax[1] >= proscenium[3] ) {
+		proscenium[3] = bbMax[1] + epsilon;
+	}
+}
+
+inline void expandProscenium (real proscenium[4], const Vec3r& point) {
+	const real epsilon = 1.0e-6;
+
+	if ( point[0] <= proscenium[0] ) {
+		proscenium[0] = point[0] - epsilon;
+	}
+
+	if ( point[1] <= proscenium[2] ) {
+		proscenium[2] = point[1] - epsilon;
+	}
+
+	if ( point[0] >= proscenium[1] ) {
+		proscenium[1] = point[0] + epsilon;
+	}
+
+	if ( point[1] >= proscenium[3] ) {
+		proscenium[3] = point[1] + epsilon;
+	}
+}
+
+};
+
+#endif // GRIDHELPERS_H
+