Pathfinder

The Base Script

<lsl> // Pathfinder PotentialField by Babbage Linden // // Part of the Pathfinder Open Source Pathfinding Demo // // The potential field maintains a representation of the navigation space // as a string containing the number of steps to the exit for each square. // The potential field lists for various commands: SETSIZE sets the size // of the navigation space, the exit and intializes the potential field; // ADDOBSTACLE and ADDOBSTACLEINDEX sets one point in the navigation space // to an obstacle that must be navigated around and updates the potential // field; NEXTPOS queries the potential field to find the next point to // for an agent at a given point to move to. When the potential field is // updated, care is taken to only update parts of the field affected by // the change and to spread the update across a number of timer events to // avoid blocking and so becoming unresponsive to NEXTPOS queries. // // Available under the Creative Commons Attribution-ShareAlike 2.5 license // http://creativecommons.org/licenses/by-sa/2.5/

integer gPotentialFieldChannel = 1; integer gDigitsPerElement = 2; integer gMinValue = 0; integer gMaxValue = 255; integer gWidth = 0; integer gHeight = 0; integer gMaxUpdates = 10;

integer gCurrentUpdateMinX; integer gCurrentUpdateMinY; integer gCurrentUpdateMaxX; integer gCurrentUpdateMaxY; integer gNextUpdateMinX; integer gNextUpdateMinY; integer gNextUpdateMaxX; integer gNextUpdateMaxY;

string gPotentialField;

integer min(integer a, integer b) {

   if(a < b)
   {
       return a;
   }
   return b;

}

integer max(integer a, integer b) {

   if(a > b)
   {
       return a;
   }
   return b;

}

string replace(string s, integer index, string newString) {

   integer newStringLength = llStringLength(newString);
   if(newStringLength)
       return  llInsertString(
                   llDeleteSubString(
                       s, 
                       index,
                       index + newStringLength - 1),
                   index, 
                   newString
               );
   return s;

}

string hexc="0123456789ABCDEF";

string int2hex(integer x) {

   integer x0 = x & 0xF;
   string res = llGetSubString(hexc, x0, x0);
   if(( x = ((x >> 4) & 0x0FFFFFFF) ))
   {
       do{
           res = llGetSubString(hexc, x0 = (x & 0xF), x0) + res;
       }while(x = x >> 4);
   }
   return res;

}

integer hex2int(string hex) {

   return (integer)("0x" + hex);

}

string setElement(string elements, integer index, integer value) {

   string stringValue = int2hex(value);
   integer len = llStringLength(stringValue);
   while(gDigitsPerElement >= ++len)
   {
       stringValue = "0" + stringValue;
   }
   //llSay(0, "setElement " + elements + " " + (string)index + " " + stringValue);
   elements = replace(elements, index * gDigitsPerElement, stringValue);
   return elements;

}

string getElementString(string elements, integer index) {

   if(index < 0)
   {
       return int2hex(gMaxValue);
   }
   return llGetSubString(elements, index * gDigitsPerElement, index * gDigitsPerElement + gDigitsPerElement - 1);

}

integer getElement(string elements, integer index) {

   return hex2int(getElementString(elements, index));

}

sayPotentialField(string elements) {

   string s = "\n";
   integer y = gHeight;
   while(0 <= --y)
   {
       integer x = -1;
       while( gWidth > ++x )
       {
           s += getElementString(elements, squareToIndex(x, y)) + " ";
       }
       s += "\n";
   }
   llSay(0,s);

}

integer squareToIndex(integer x, integer y) {

   if(x < 0 || x >= gWidth || y < 0 || y >= gHeight)
   {
       return -1;
   }
   
   return x + y * gWidth;

}

string addObstacle(string elements, integer x, integer y) {

   elements = setElement(elements, squareToIndex(x, y), gMaxValue);
   expandUpdateRegion(x, y);
   return updatePotentialField(elements);

}

expandUpdateRegion(integer x, integer y) {

   gNextUpdateMinX = min(gNextUpdateMinX, x - 1);
   gNextUpdateMinX = max(gNextUpdateMinX, 0);
   gNextUpdateMinY = min(gNextUpdateMinY, y - 1);
   gNextUpdateMinY = max(gNextUpdateMinY, 0);
   gNextUpdateMaxX = max(gNextUpdateMaxX, x + 1);
   gNextUpdateMaxX = min(gNextUpdateMaxX, gWidth - 1);
   gNextUpdateMaxY = max(gNextUpdateMaxY, y + 1);
   gNextUpdateMaxY = min(gNextUpdateMaxY, gHeight - 1);

}

resetNextUpdateRegion() {

   gNextUpdateMinX = gWidth - 1;
   gNextUpdateMinY = gHeight - 1;
   gNextUpdateMaxX = 0;
   gNextUpdateMaxY = 0;

}

string updatePotentialField(string elements) {

   // If current update region finished, switch to next region.
   if(gCurrentUpdateMinY > gCurrentUpdateMaxY)
   {
       gCurrentUpdateMinX = gNextUpdateMinX;
       gCurrentUpdateMinY = gNextUpdateMinY;
       gCurrentUpdateMaxX = gNextUpdateMaxX;
       gCurrentUpdateMaxY = gNextUpdateMaxY;
       resetNextUpdateRegion();
       
       // If next region empty, stop updating.
       if(gCurrentUpdateMinY > gCurrentUpdateMaxY)
       {
           llSay(0, "updatePotentialField:DONE");
           llSetTimerEvent(0.0);
           return elements;
       }
       
       llSay(0, "updatePotentialField:(" + (string)gCurrentUpdateMinX + "," + (string)gCurrentUpdateMinY + ") 
          (" + (string)gCurrentUpdateMaxX + "," + (string)gCurrentUpdateMaxY + ")");
   }
   
   // Recalculate potentials.
   llResetTime();
   integer updates = 0;
   if(gCurrentUpdateMinX <= gCurrentUpdateMaxX)
   {
       while((updates < gMaxUpdates) && (gCurrentUpdateMinY <= gCurrentUpdateMaxY))
       {
           //llSay(0, "updatePotentialField:" + (string)gCurrentUpdateMinY);
           integer x = gCurrentUpdateMinX;
           do{
               elements = calculatePotentialField(elements, x, gCurrentUpdateMinY);
           }while(gCurrentUpdateMaxX >= ++x);
           //x = gCurrentUpdateMaxX + 1; this saves us from doing "++updates;" in the loop
           updates += x - gCurrentUpdateMinX;
           ++gCurrentUpdateMinY;
       }
   }
   
   llSetTimerEvent((llGetTime() * 2.0) + 0.1);
   return elements;

}

string calculatePotentialField(string elements, integer x, integer y) {

   integer currentValue = getElement(elements, squareToIndex(x, y));
   
   // Don't update obstacles or exits.
   if(currentValue == gMaxValue || currentValue == gMinValue)
   {
       return elements;
   }

   integer minValue = gMaxValue;
   minValue = min(minValue, getElement(elements, squareToIndex(x - 1, y)));
   minValue = min(minValue, getElement(elements, squareToIndex(x + 1, y)));
   minValue = min(minValue, getElement(elements, squareToIndex(x, y - 1)));
   minValue = min(minValue, getElement(elements, squareToIndex(x, y + 1)));
   minValue = min(minValue + 1, gMaxValue - 1);
   if(minValue != currentValue)
   {
       //llSay(0, "calculatePotentialField:" + (string)x + "," + (string)y + " currentValue " + (string)currentValue + " newValue " + (string)minValue);
       elements = setElement(elements, squareToIndex(x, y), minValue);
       expandUpdateRegion(x, y);
   }
   return elements;

}

string nextStep(string elements, integer x, integer y) {

   integer nextX;
   integer nextY;
   integer minValue = gMaxValue;
   integer currentX = x - 1;
   integer currentY = y;
   integer currentValue = getElement(elements, squareToIndex(currentX, currentY));
   if(currentValue < minValue)
   {
       minValue = currentValue;
       nextX = currentX;
       nextY = currentY;
   }
   currentX = x + 1;
   currentValue = getElement(elements, squareToIndex(currentX, currentY));
   if(currentValue < minValue)
   {
       minValue = currentValue;
       nextX = currentX;
       nextY = currentY;
   }
   currentX = x;
   currentY = y - 1;
   currentValue = getElement(elements, squareToIndex(currentX, currentY));
   if(currentValue < minValue)
   {
       minValue = currentValue;
       nextX = currentX;
       nextY = currentY;
   }
   currentY = y + 1;
   currentValue = getElement(elements, squareToIndex(currentX, currentY));
   if(currentValue < minValue)
   {
       minValue = currentValue;
       nextX = currentX;
       nextY = currentY;
   }
   if(minValue == gMaxValue)
   {
       return "";
   }
   return (string)nextX + "," + (string)nextY;

}

setSize(integer width, integer height, integer exitX, integer exitY) {

   gWidth = width;
   gHeight = height;
   
   gPotentialField = "";

   integer y = -1;
   while(height > ++y)
   {
       integer x = -1;
       while(width > ++x)
       {
           gPotentialField = setElement(gPotentialField, squareToIndex(x, y), llAbs(exitX - x) + llAbs(exitY - y));
       }
   }
   resetNextUpdateRegion();
   sayPotentialField(gPotentialField);

}

init() {

   llListen(0, "", NULL_KEY, "");
   llListen(gPotentialFieldChannel, "", NULL_KEY, "");

}

default {

   state_entry()
   {
       init();
   }
   
   on_rez(integer param)
   {
       init();
   }
   
   timer()
   {
       gPotentialField = updatePotentialField(gPotentialField);
   }
   
   listen(integer channel, string name, key id, string s)
   {
       list message = llCSV2List(s);
       string command = llList2String(message, 0);
       integer x = llList2Integer(message, 1);
       integer y = llList2Integer(message, 2);
       if(command == "ADDOBSTACLE")
       {
           gPotentialField = addObstacle(gPotentialField, x, y);
       }
       else if(command == "ADDOBSTACLEINDEX")
       {
           y = x / gWidth;
           x %= gWidth;
           gPotentialField = addObstacle(gPotentialField, x, y);
       }
       else if(command == "SETSIZE")
       {
           integer width = x;
           integer height = y;
           x = llList2Integer(message, 3);
           y = llList2Integer(message, 4);
           setSize(width, height, x, y);
       }
       else if(command == "NEXTPOS")
       {
           integer channel = llList2Integer(message, 3);
           if(getElement(gPotentialField, squareToIndex(x, y)) == 0)
           {
               llSay(channel, "RESET");
           }
           string nextStepString = nextStep(gPotentialField, x, y);
           if(llStringLength(nextStepString) > 0)
           {
               list nextStepList = llCSV2List(nextStepString);
               x = llList2Integer(nextStepList, 0);
               y = llList2Integer(nextStepList, 1);
               llSay(channel, "NEXTPOS," + (string)x + "," + (string)y);
           }
       }
       //sayPotentialField(gPotentialField);
   }

} </lsl>

The Rezzer Script

<lsl> // Pathfinder Rezzer by Babbage Linden // // Part of the Pathfinder Open Source Pathfinding Demo // // The rezzer listens for SETSIZE commands, which causes it to rez // a grid of Square objects of the appropriate size and set the // entry and exit points as exits. Touching the rezzer // causes it to rez and agent above the entry point at the origin. // // Available under the Creative Commons Attribution-ShareAlike 2.5 license // http://creativecommons.org/licenses/by-sa/2.5/

float gSquareWidth = 1.0; float gPeriod = 5.0; vector gOrigin; vector gEntrance; integer gEntranceX; integer gEntranceY; integer gPopulation = 0; integer gMaxPopulation = 10; integer gPotentialFieldChannel = 1; integer gSquareChannel = 2; integer gAgentChannel = 3;

init() {

   llListen(0, "", NULL_KEY, "");

}

default {

   state_entry()
   {
       init();
   }
   
   on_rez(integer param)
   {
       init();
   }
   
   listen(integer channel, string name, key id, string s)
   {
       list message = llCSV2List(s);
       string command = llList2String(message, 0);
       integer x = llList2Integer(message, 1);
       integer y = llList2Integer(message, 2);
       if(command == "SETSIZE")
       {
           integer width = x;
           integer height = y;
           integer exitX = llList2Integer(message, 3);
           integer exitY = llList2Integer(message, 4);
           gEntranceX = llList2Integer(message, 5);
           gEntranceY = llList2Integer(message, 6);
           gOrigin = llGetPos();
           gOrigin.x -= ((width - 1) * gSquareWidth) / 2.0;
           gOrigin.y -= ((height - 1) * gSquareWidth) / 2.0;
           gEntrance = gOrigin;
           gEntrance.x += gEntranceX * gSquareWidth;
           gEntrance.y += gEntranceY * gSquareWidth;
           gEntrance.z += 1.0;
           for(y = 0; y < height; ++y)
           {
               for(x = 0; x < width; ++x)
               {
                   vector pos = gOrigin;
                   pos.x += x * gSquareWidth;
                   pos.y += y * gSquareWidth;
                   pos.z += 0.5;
                   integer channel = (x + y * width);
                   llRezObject("Square", pos, <0,0,0>, <0,0,0,0>, channel);
               }
           }
           llSay(gSquareChannel, "EXIT," + (string)(gEntranceX + gEntranceY * width));
           llSay(gSquareChannel, "EXIT," + (string)(exitX + exitY * width));
           gAgentChannel = 3;
           gMaxPopulation = 10;
           llSetTimerEvent(gPeriod);
       }
       else if(command == "RESET")
       {
           gPopulation = 0;
           llSay(gSquareChannel, "RESET");
           integer channel;
           for(channel = 2; channel <= gAgentChannel; ++channel)
           {
               llSay(channel, "RESET");
           }
           llSetTimerEvent(0);
           gMaxPopulation = 0;
       }
       else if(command == "FINISHED")
       {
           --gPopulation;
           if(gPopulation < 0) {gPopulation = 0;}
           llSetTimerEvent(gPeriod);
           //llSay(0,"Population:" + (string)gPopulation);
       }
   }
   
   timer()
   {
       if(gPopulation >= gMaxPopulation)
       {
           llSetTimerEvent(0);
           return;
       }
       integer channel = gAgentChannel++;
       llRezObject("Agent", gEntrance, <0,0,0>, <0,0,0,0>, channel);
       llSay(channel, "POS," + (string)gEntranceX + "," + (string)gEntranceY);
       ++gPopulation;
       //llSay(0,"Population:" + (string)gPopulation);
   }

} </lsl>

The Agent Script

<lsl> // Pathfinder Agent by Babbage Linden // // Part of the Pathfinder Open Source Pathfinding Demo // // The agent periodically makes NEXTPOS queries to the PotentialField // script to find the next point to move to and can have its current // position set with the POS command. // // Available under the Creative Commons Attribution-ShareAlike 2.5 license // http://creativecommons.org/licenses/by-sa/2.5/

float gSquareWidth = 1.0; float gStartPeriod = 2.0; float gPeriod = 2.0; integer gChannel; integer gX; integer gY; integer gSquareChannel = 2; integer gPotentialFieldChannel = 1;

default {

   on_rez(integer param)
   {
       gChannel = param;
       llListen(gChannel, "", NULL_KEY, "");
   }
   
   listen(integer channel, string name, key id, string s)
   {
       list message = llCSV2List(s);
       string command = llList2String(message, 0);
       integer x = llList2Integer(message, 1);
       integer y = llList2Integer(message, 2);
       if(command == "POS")
       {
           gX = x;
           gY = y;
           llSetTimerEvent(gPeriod);
       }
       else if(command == "NEXTPOS")
       {
           integer dX = x - gX;
           integer dY = y - gY;
           vector pos = llGetPos();
           pos.x += dX * gSquareWidth;
           pos.y += dY * gSquareWidth;
           llSetPos(pos);
           gX = x;
           gY = y;
           gPeriod = gStartPeriod;
           llSetTimerEvent(gPeriod);
       }
       else if(command == "RESET")
       {
           llSay(0,"FINISHED");
           llDie();
       }
   }
   
   timer()
   {
       llSay(gPotentialFieldChannel, "NEXTPOS," + (string)gX + "," + (string)gY + "," + (string)gChannel);
       gPeriod *= 2.0;
       llSetTimerEvent(gPeriod);
   }

} </lsl>

The Square Script

<lsl> // Pathfinder Square by Babbage Linden // // Part of the Pathfinder Open Source Pathfinding Demo for Second Life // // The square listens for various commands: RESET causes it to kill itself; // EXIT causes it to turn black and set itself as an exit. Touching the // causes it to grow and to send the ADDOBSTACLEINDEX command to the // PotentialField script. // // Available under the Creative Commons Attribution-ShareAlike 2.5 license // http://creativecommons.org/licenses/by-sa/2.5/

integer gSquareChannel = 2; integer gPotentialFieldChannel = 1; integer gIndex; integer STATE_DEFAULT = 0; integer STATE_OBSTACLE = 1; integer STATE_EXIT = 2; integer gState = STATE_DEFAULT;

default {

   on_rez(integer param)
   {
       gIndex = param;
       llListen(gSquareChannel, "", NULL_KEY, "");
   }
   
   touch_start(integer num)
   {
       if(gState == STATE_DEFAULT)
       {
           llSay(gPotentialFieldChannel, "ADDOBSTACLEINDEX," + (string)gIndex);
           llSetScale(<1,1,1>);
           llSetPos(llGetPos() + <0,0,0.5>);
           gState = STATE_OBSTACLE;
       }
   }
   
   listen(integer channel, string name, key id, string s)
   {
       list message = llCSV2List(s);
       string command = llList2String(message, 0);
       if(command == "RESET")
       {
           llDie();
       }
       else if(command == "EXIT")
       {
           integer index = llList2Integer(message, 1);
           if(index == gIndex)
           {
               llSetColor(<0,0,0>, ALL_SIDES);
               gState = STATE_EXIT;
           }
       }
       else if(command == "ENTRANCE")
       {
           integer index = llList2Integer(message, 1);
           if(index == gIndex)
           {
               llSetTexture("5748decc-f629-461c-9a36-a35a221fe21f", ALL_SIDES);
               gState = STATE_EXIT;
           }
       }
   }

} </lsl>