Fixed the run away terrain generation when encountering unknown tiles…

…, added support for tile randomness factor.

examples/desert.tsx

@@ -37,14 +37,22 @@
  <tile id="27" terrain="1,0,1,1"/>
  <tile id="28" terrain="0,1,1,1"/>
  <tile id="29" terrain="0,0,0,0"/>
+ <tile id="30" terrain="0,0,0,0" probability="0.5"/>
+ <tile id="31" terrain="0,0,0,0" probability="0.5"/>
  <tile id="32" terrain="0,2,0,2"/>
  <tile id="33" terrain="2,2,2,2"/>
  <tile id="34" terrain="2,0,2,0"/>
  <tile id="35" terrain="2,2,2,0"/>
  <tile id="36" terrain="2,2,0,2"/>
+ <tile id="37" terrain="0,0,0,0" probability="0.5"/>
+ <tile id="38" terrain="0,0,0,0" probability="0.5"/>
+ <tile id="39" terrain="0,0,0,0" probability="0.5"/>
  <tile id="40" terrain="0,2,0,0"/>
  <tile id="41" terrain="2,2,0,0"/>
  <tile id="42" terrain="2,0,0,0"/>
  <tile id="43" terrain="2,0,2,2"/>
  <tile id="44" terrain="0,2,2,2"/>
+ <tile id="45" terrain="0,0,0,0" probability="0"/>
+ <tile id="46" terrain="0,0,0,0" probability="0.5"/>
+ <tile id="47" terrain="0,0,0,0" probability="0.5"/>
 </tileset>

src/libtiled/mapreader.cpp

@@ -327,13 +327,13 @@ void MapReaderPrivate::readTilesetTile(Tileset *tileset)
         xml.raiseError(tr("Invalid tile ID: %1").arg(id));
         return;
     }
+    Tile *tile = tileset->tileAt(id);
 
     // TODO: Add support for individual tiles (then it needs to be added here)
 
     // Read tile quadrant terrain ids
     QString terrain = atts.value(QLatin1String("terrain")).toString();
     if (!terrain.isEmpty()) {
-        Tile *tile = tileset->tileAt(id);
         QStringList quadrants = terrain.split(QLatin1String(","));
         if (quadrants.size() == 4) {
             for (int i = 0; i < 4; ++i) {
@@ -343,9 +343,14 @@ void MapReaderPrivate::readTilesetTile(Tileset *tileset)
         }
     }
 
+    // Read tile probability
+    QString probability = atts.value(QLatin1String("probability")).toString();
+    if (!probability.isEmpty()) {
+        tile->setTerrainProbability(probability.toFloat());
+    }
+
     while (xml.readNextStartElement()) {
         if (xml.name() == "properties") {
-            Tile *tile = tileset->tileAt(id);
             tile->mergeProperties(readProperties());
         } else {
             readUnknownElement();

src/libtiled/mapwriter.cpp

@@ -307,11 +307,15 @@ void MapWriterPrivate::writeTileset(QXmlStreamWriter &w, const Tileset *tileset,
         const Tile *tile = tileset->tileAt(i);
         const Properties properties = tile->properties();
         unsigned int terrain = tile->terrain();
-        if (!properties.isEmpty() || terrain != 0xFFFFFFFF) {
+        int probability = tile->terrainProbability();
+
+        if (!properties.isEmpty() || terrain != 0xFFFFFFFF || probability != -1) {
             w.writeStartElement(QLatin1String("tile"));
             w.writeAttribute(QLatin1String("id"), QString::number(i));
             if (terrain != 0xFFFFFFFF)
                 w.writeAttribute(QLatin1String("terrain"), makeTerrainAttribute(tile));
+            if (probability != -1)
+                w.writeAttribute(QLatin1String("probability"), QString::number(probability));
             if (!properties.isEmpty())
                 writeProperties(w, properties);
             w.writeEndElement();

src/libtiled/tile.h

@@ -44,7 +44,8 @@ class TILEDSHARED_EXPORT Tile : public Object
         mId(id),
         mTileset(tileset),
         mImage(image),
-        mTerrain(-1)
+        mTerrain(-1),
+        mTerrainProbability(-1.f)
     {}
 
     /**
@@ -111,11 +112,22 @@ class TILEDSHARED_EXPORT Tile : public Object
     unsigned short rightEdge() const { return ((terrain() >> 8) & 0xFF00) | (terrain() & 0xFF); }
     unsigned int terrain() const { return this == NULL ? 0xFFFFFFFF : mTerrain; } // HACK: NULL Tile has 'none' terrain type.
 
+    /**
+     * Returns the probability of this terrain type appearing while painting (0-100%).
+     */
+    float terrainProbability() const { return mTerrainProbability; }
+
+    /**
+     * Set the probability of this terrain type appearing while painting (0-100%).
+     */
+    void setTerrainProbability(float probability) { mTerrainProbability = probability; }
+
 private:
     int mId;
     Tileset *mTileset;
     QPixmap mImage;
     unsigned int mTerrain;
+    float mTerrainProbability;
 };
 
 } // namespace Tiled

src/tiled/terrainbrush.cpp

@@ -290,18 +290,25 @@ Tile *TerrainBrush::findBestTile(Tileset *tileset, unsigned int terrain, unsigne
     QList<Tile*> matches;
     int penalty = INT_MAX;
 
+    // TODO: this is a slow linear search, perhaps we could use a better find algorithm...
     int tileCount = tileset->tileCount();
     for (int i = 0; i < tileCount; ++i) {
         Tile *t = tileset->tileAt(i);
         if ((t->terrain() & considerationMask) != (terrain & considerationMask))
             continue;
 
-        // calculate the tile transition penalty
-        int transitionPenalty = tileset->terrainTransitionPenalty(t->terrain() >> 24, terrain >> 24);
-        transitionPenalty += tileset->terrainTransitionPenalty((t->terrain() >> 16) & 0xFF, (terrain >> 16) & 0xFF);
-        transitionPenalty += tileset->terrainTransitionPenalty((t->terrain() >> 8) & 0xFF, (terrain >> 8) & 0xFF);
-        transitionPenalty += tileset->terrainTransitionPenalty(t->terrain() & 0xFF, terrain & 0xFF);
+        // calculate the tile transition penalty based on shortest distance to target terrain type
+        int tr = tileset->terrainTransitionPenalty(t->terrain() >> 24, terrain >> 24);
+        int tl = tileset->terrainTransitionPenalty((t->terrain() >> 16) & 0xFF, (terrain >> 16) & 0xFF);
+        int br = tileset->terrainTransitionPenalty((t->terrain() >> 8) & 0xFF, (terrain >> 8) & 0xFF);
+        int bl = tileset->terrainTransitionPenalty(t->terrain() & 0xFF, terrain & 0xFF);
 
+        // if there is no path to the destination terrain, this isn't a useful transition
+        if (tr < 0 || tl < 0 || br < 0 || bl < 0)
+            continue;
+
+        // add tile to the candidate list
+        int transitionPenalty = tr + tl + br + bl;
         if (transitionPenalty <= penalty) {
             if (transitionPenalty < penalty)
                 matches.clear();
@@ -312,9 +319,34 @@ Tile *TerrainBrush::findBestTile(Tileset *tileset, unsigned int terrain, unsigne
     }
 
     // choose a candidate at random, with consideration for terrain probability
-    if (!matches.isEmpty())
-        return matches[0];
+    if (!matches.isEmpty()) {
+        float random = ((float)rand() / RAND_MAX) * 100.f;
+        float total = 0, unassigned = 0;
+
+        // allow the tiles with assigned probability to take their share
+        for (int i = 0; i < matches.size(); ++i) {
+            float probability = matches[i]->terrainProbability();
+            if (probability < 0.f) {
+                ++unassigned;
+                continue;
+            }
+            if (random < total + probability)
+                return matches[i];
+            total += probability;
+        }
+
+        // divide the remaining percentile by the numer of unassigned tiles
+        float remainingShare = (100.f - total) / (float)unassigned;
+        for (int i = 0; i < matches.size(); ++i) {
+            if (matches[i]->terrainProbability() >= 0.f)
+                continue;
+            if (random < total + remainingShare)
+                return matches[i];
+            total += remainingShare;
+        }
+    }
 
+    // TODO: conveniently, the NULL tile doesn't currently work, but when it does, we need to signal a failure to find any matches some other way
     return NULL;
 }
 
@@ -388,7 +420,7 @@ void TerrainBrush::updateBrush(const QPoint &cursorPos, const QVector<QPoint> *l
 
             --initialTiles;
         } else {
-            // following tiles each need consideration against their surroundings
+            // tiles each need consideration against their surroundings
             preferredTerrain = tile->terrain();
             mask = 0;