[Scummvm-cvs-logs] SF.net SVN: scummvm:[45623] scummvm/trunk/engines/draci

[spalek at users.sourceforge.net]

Revision: 45623
          http://scummvm.svn.sourceforge.net/scummvm/?rev=45623&view=rev
Author:   spalek
Date:     2009-11-03 03:38:28 +0000 (Tue, 03 Nov 2009)

Log Message:
-----------
Run the path obliqueing process repeatedly until it converges.

Modified Paths:
--------------
    scummvm/trunk/engines/draci/walking.cpp
    scummvm/trunk/engines/draci/walking.h

Modified: scummvm/trunk/engines/draci/walking.cpp
===================================================================
--- scummvm/trunk/engines/draci/walking.cpp	2009-11-03 03:24:59 UTC (rev 45622)
+++ scummvm/trunk/engines/draci/walking.cpp	2009-11-03 03:38:28 UTC (rev 45623)
@@ -303,53 +303,10 @@
 		}
 	}
 
-	// Making the path oblique works as follows.  If the path has at least
-	// 3 remaining vertices, we try to oblique the L-shaped path between
-	// them.  First we try to connect the 1st and 3rd vertex directly (if
-	// all points on the line between them are walkable) and then we try to
-	// walk on both edges towards the 2nd vertex in parallel and try to
-	// find a shortcut (replacing the 2nd vertex by this mid-point).  If
-	// either of those attempts succeeds, we have shortned the path.  We
-	// update the path vertices and continue with the next segment.
-	for (uint head = 2; head < obliquedPath->size(); ++head) {
-		const Common::Point &v1 = (*obliquedPath)[head-2];
-		const Common::Point &v2 = (*obliquedPath)[head-1];
-		const Common::Point &v3 = (*obliquedPath)[head];
-		const int points12 = pointsBetween(v1, v2);
-		const int points32 = pointsBetween(v3, v2);
-		// Find the first point p on each edge [v1, v2] and [v3, v2]
-		// such that the edge [p, the third vertex] is covered.
-		// Ideally we would like p \in {v1, v3} and the closer the
-		// better.  The last point p = v2 should always succeed.
-		int first12, first32;
-		for (first12 = 0; first12 < points12; ++first12) {
-			Common::Point midPoint = interpolate(v1, v2, first12, points12);
-			if (lineIsCovered(midPoint, v3)) {
-				break;
-			}
-		}
-		if (first12 == 0) {
-			// Can completely remove the vertex.  Head stays the
-			// same after -- and ++.
-			obliquedPath->remove_at(--head);
-			continue;
-		}
-		for (first32 = 0; first32 < points32; ++first32) {
-			Common::Point midPoint = interpolate(v3, v2, first32, points32);
-			if (lineIsCovered(midPoint, v1)) {
-				break;
-			}
-		}
-		if (first12 < points12 && first32 >= points32 + MIN(first12 - points12, 0)) {
-			// There is such a point on the first edge and the
-			// second edge has either not succeeded or we gain more
-			// by cutting this edge than the other one.
-			(*obliquedPath)[head-1] = interpolate(v1, v2, first12, points12);
-			// After replacing the 2nd vertex, let head move on.
-		} else if (first32 < points32) {
-			(*obliquedPath)[head-1] = interpolate(v3, v2, first32, points32);
-		}
-	}
+	// Repeatedly oblique the path until it cannot be improved.  This
+	// process is finite, because after each success the number of vertices
+	// goes down.
+	while (managedToOblique(obliquedPath)) {}
 }
 
 Sprite *WalkingMap::newOverlayFromPath(const WalkingPath &path, byte colour) const {
@@ -409,4 +366,58 @@
 	return true;
 }
 
+bool WalkingMap::managedToOblique(WalkingPath *path) const {
+	bool improved = false;
+
+	// Making the path oblique works as follows.  If the path has at least
+	// 3 remaining vertices, we try to oblique the L-shaped path between
+	// them.  First we try to connect the 1st and 3rd vertex directly (if
+	// all points on the line between them are walkable) and then we try to
+	// walk on both edges towards the 2nd vertex in parallel and try to
+	// find a shortcut (replacing the 2nd vertex by this mid-point).  If
+	// either of those attempts succeeds, we have shortned the path.  We
+	// update the path vertices and continue with the next segment.
+	for (uint head = 2; head < path->size(); ++head) {
+		const Common::Point &v1 = (*path)[head-2];
+		const Common::Point &v2 = (*path)[head-1];
+		const Common::Point &v3 = (*path)[head];
+		const int points12 = pointsBetween(v1, v2);
+		const int points32 = pointsBetween(v3, v2);
+		// Find the first point p on each edge [v1, v2] and [v3, v2]
+		// such that the edge [p, the third vertex] is covered.
+		// Ideally we would like p \in {v1, v3} and the closer the
+		// better.  The last point p = v2 should always succeed.
+		int first12, first32;
+		for (first12 = 0; first12 < points12; ++first12) {
+			Common::Point midPoint = interpolate(v1, v2, first12, points12);
+			if (lineIsCovered(midPoint, v3)) {
+				break;
+			}
+		}
+		if (first12 == 0) {
+			// Can completely remove the vertex.  Head stays the
+			// same after -- and ++.
+			path->remove_at(--head);
+			improved = true;
+			continue;
+		}
+		for (first32 = 0; first32 < points32; ++first32) {
+			Common::Point midPoint = interpolate(v3, v2, first32, points32);
+			if (lineIsCovered(midPoint, v1)) {
+				break;
+			}
+		}
+		if (first12 < points12 && first32 >= points32 + MIN(first12 - points12, 0)) {
+			// There is such a point on the first edge and the
+			// second edge has either not succeeded or we gain more
+			// by cutting this edge than the other one.
+			(*path)[head-1] = interpolate(v1, v2, first12, points12);
+			// After replacing the 2nd vertex, let head move on.
+		} else if (first32 < points32) {
+			(*path)[head-1] = interpolate(v3, v2, first32, points32);
+		}
+	}
+	return improved;
 }
+
+}

Modified: scummvm/trunk/engines/draci/walking.h
===================================================================
--- scummvm/trunk/engines/draci/walking.h	2009-11-03 03:24:59 UTC (rev 45622)
+++ scummvm/trunk/engines/draci/walking.h	2009-11-03 03:38:28 UTC (rev 45623)
@@ -68,6 +68,9 @@
 	int pointsBetween(const Common::Point &p1, const Common::Point &p2) const;
 	Common::Point interpolate(const Common::Point &p1, const Common::Point &p2, int i, int n) const;
 	bool lineIsCovered(const Common::Point &p1, const Common::Point &p2) const;
+
+	// Returns true if the number of vertices on the path was decreased.
+	bool managedToOblique(WalkingPath *path) const;
 };
 
 /*


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