world.java

《J2ME Game Programming》随书光盘源代码

import net.jscience.math.kvm.MathFP;

import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Image;


public class World
{
   public static final int TILE_WIDTH=32;
   public static final int TILE_HEIGHT=32;

   public static final int TILE_WIDTH_FP = MathFP.toFP(TILE_WIDTH);
   public static final int TILE_HEIGHT_FP = MathFP.toFP(TILE_HEIGHT);

	public static final int TILE_HALF_HEIGHT = TILE_HEIGHT / 2;
	public static final int TILE_HALF_WIDTH = TILE_WIDTH / 2;

   private int tilesWide = 20;
   private int tilesHigh = 20;
   private byte[][] tileMap;

   private int viewWidth;
   private int viewHeight;

	// tile types
	public static final byte NO_TILE = 0;
   private long lastCycleTime;

   // raytracer
   private int columnsPerDegree;

   static int[] lookupDistortionFP;

   private int projWallHeight;

   static int WALL_HEIGHT = TILE_WIDTH*2;  // makes walls twice as high as
                                           // they are wide
   static int PROJ_PLANE_HEIGHT = 128;
   static int PROJ_PLANE_HEIGHT_CENTER = PROJ_PLANE_HEIGHT/2;
   static int EDGE_IGNORE_FP = MathFP.toFP(5);
   static int HORIZON_DISTANCE_FP = MathFP.toFP(TILE_WIDTH * 10 * 2);

   private int focalDistance;
   private int fovColumns;
   private int halfFovColumns;   // precalced cause we use it a bit

   private Image background;
   private Actor player;

   // lookup table for trig values (0 to 359)
   public static int[] lookupCosFP = new int[360];
   public static int[] lookupSinFP = new int[360];
   public static int[] lookupTanFP = new int[360];

   // static init
   {
      for (int i = 0; i < 360; i++)
      {
         // build an array of precalculated trig values (much faster to just
         // look them up here) note we add 0.01 to avoid all divide by zero
         // cases.
         lookupCosFP[i] = MathFP.cos(MathFP.add(MathFP.toFP("0.01"), Actor.getRadiansFPFromAngle(i)));
         lookupSinFP[i] = MathFP.sin(MathFP.add(MathFP.toFP("0.01"), Actor.getRadiansFPFromAngle(i)));
         lookupTanFP[i] = MathFP.tan(MathFP.add(MathFP.toFP("0.01"), Actor.getRadiansFPFromAngle(i)));
      }
  }


   public World(int viewWidthArg, int viewHeightArg, Actor p)
   {
      player = p;
      viewWidth = viewWidthArg;
      viewHeight = viewHeightArg;

      // calculate field of view (60 degrees is ideal, but we need to base
      // it on how many columns we can display in terms of pixels
      columnsPerDegree = viewWidth / 60;
      fovColumns = viewWidth / columnsPerDegree;
      halfFovColumns = fovColumns / 2;

      // calculate the focal distance
      int distFP = MathFP.div( MathFP.toFP(viewWidth/2), lookupTanFP[halfFovColumns] );
      focalDistance = MathFP.toInt(distFP);

      projWallHeight =  MathFP.toFP(WALL_HEIGHT * focalDistance);

      //#ifdef debug
      System.out.println("Focal distance: " + focalDistance);
      System.out.println("FOV columns: " + fovColumns);
      System.out.println("Degrees per column: " + columnsPerDegree);
      //#endif

      // precalculate the distortion values
      lookupDistortionFP = new int[fovColumns+1];
      for (int i = -halfFovColumns; i <= halfFovColumns; i++)
         lookupDistortionFP[i+halfFovColumns] =
                 MathFP.div(MathFP.toFP(1),
                 MathFP.cos(Actor.getRadiansFPFromAngle(i)));

      // some pretty clouds
      background = ImageSet.loadClippedImage("/background.png", 0, 0);

      // setup the map
      tileMap = new byte[20][20];

      // side walls
      for (int tx=0; tx < 20; tx++)
      {
         tileMap[0][tx] = 1;
         tileMap[19][tx] = 1;
      }

      // top and bottom walls
      for (int ty=0; ty < 20; ty++)
      {
         tileMap[ty][0] = 1;
         tileMap[ty][19] = 1;
      }

      // pillars every four tiles
      for (int ty=0; ty < 20; ty+=4)
         for (int tx=0; tx < 20; tx+=4)
            tileMap[ty][tx] = 1;

   }

   protected final void cycle()
   {
      if (lastCycleTime > 0)
      {
         long msSinceLastCycle = System.currentTimeMillis() - lastCycleTime;
         player.cycle(msSinceLastCycle);
      }

      lastCycleTime = System.currentTimeMillis();
   }



	public final int getTileXCenter(int x)
	{
		return (getTileX(x) * TILE_WIDTH) + (TILE_WIDTH / 2);
	}

	public final int getTileYCenter(int y)
	{
		return (getTileY(y) * TILE_HEIGHT) + (TILE_HEIGHT / 2);
	}

	public final int getTileX(int x) { return x / TILE_WIDTH; }
	public final int getTileY(int y) { return y / TILE_HEIGHT; }

   public final byte getTile(int x, int y)
	{
		int tx = getTileX(x);
		int ty = getTileY(y);
		if (tx < 0 || tx >= tilesWide || ty < 0 || ty >= tilesHigh) return -1;
      return tileMap[ ty ][ tx ];
	}

   private boolean isWall(int px, int py)
   {
      if ( getTile( px, py ) == 1)
         return true;
      return false;
   }

   private boolean isOnMap(int px, int py)
   {
      if (px < 0 || py < 0) return false;
      if (px > TILE_WIDTH * tilesWide) return false;
      if (py > TILE_HEIGHT * tilesHigh) return false;
      return true;
   }

   private int angleChange(int a, int change)
   {
      int angle = a + change;
      if (angle > 359) angle -= 360;
      if (angle < 0) angle = 360 - Math.abs(angle);
      return angle;
   }

   private int getDistanceFP(int dxFP, int dyFP, int angle)
   {
      int distanceFP = 0;
      if ( MathFP.abs(dxFP) > MathFP.abs(dyFP) )
         distanceFP = MathFP.div(MathFP.abs(dxFP), lookupCosFP[angle]);
      else
         distanceFP = MathFP.div(MathFP.abs(dyFP), lookupSinFP[angle]);
      return MathFP.abs(distanceFP);
   }

   private static boolean lastHitWasVert=false;

   public final void render(Graphics g)
   {
      // draw the background
      g.drawImage(background, 0, 0, Graphics.TOP|Graphics.LEFT);

      /////////////////////////////////////////////////////////////////////////
      // RAYCASTING
      /////////////////////////////////////////////////////////////////////////

      int startingXFP = MathFP.toFP(player.getX());
      int startingYFP = MathFP.toFP(player.getY());
      int startingX = player.getX();
      int startingY = player.getY();

      int rayAngle=angleChange(player.getDirection(), halfFovColumns);
      int pixelColumn = 0;
      int destinationXFP=0,destinationYFP=0;
      int originXFP=0,originYFP=0;

      for (int castColumn=0; castColumn < fovColumns; castColumn++)
      {
         rayAngle = angleChange(rayAngle, -1);

         // --------------- HORIZONTAL RAY ------------------
         // try casting a horizontal line until we get a hit

         boolean gotHorizHit = false;
         int horizDistanceFP = 0;

         // if the ray can possibly hit a horizontal line
         if (rayAngle != 0 && rayAngle != 180)
         {
            // cast the first ray to the intersection point
            // figure out the coord of the vert tile line we're after
            // (based on whether we're looking left or right). Note we offset
            // by one pixel so we know we're *inside* a tile cell
            if (rayAngle > 180)
               originYFP = MathFP.toFP( (((startingY / TILE_HEIGHT) +1) * TILE_HEIGHT) + 1 );
            else
               originYFP = MathFP.toFP(((startingY / TILE_HEIGHT) * TILE_HEIGHT) - 1);

            destinationYFP = MathFP.sub(startingYFP, originYFP);
            destinationXFP = MathFP.div(destinationYFP, lookupTanFP[rayAngle]);
            originXFP = MathFP.add(startingXFP, destinationXFP);

            // get the distance to the first grid cell
            horizDistanceFP = getDistanceFP(destinationXFP, destinationYFP, rayAngle);

            while (!gotHorizHit)
            {
               // abort if we're past the horizon
               if (horizDistanceFP > HORIZON_DISTANCE_FP) break;

               // did we hit a wall?
               if (isWall(MathFP.toInt(originXFP), MathFP.toInt(originYFP)))
               {
                  gotHorizHit = true;
                  break;
               }

               // are we still on the map?
               if (!isOnMap(MathFP.toInt(originXFP), MathFP.toInt(originYFP)))
                  break;

               int lastXFP = originXFP;
               int lastYFP = originYFP;

               // project to the next point along
               if (rayAngle > 180)  // if ray going down
                  originYFP = MathFP.add(lastYFP, TILE_HEIGHT_FP);
               else                 // if ray going up
                  originYFP = MathFP.sub(lastYFP, TILE_HEIGHT_FP);

               destinationYFP = MathFP.sub(lastYFP, originYFP);
               destinationXFP = MathFP.div(destinationYFP, lookupTanFP[rayAngle]);

               // move out to the next tile position
               originXFP = MathFP.add(lastXFP, destinationXFP);

               // add the distance to our running total
               horizDistanceFP = MathFP.add(horizDistanceFP,
                                            getDistanceFP(destinationXFP, destinationYFP, rayAngle));
            }
         }

         if (gotHorizHit)
         {
            // got a hit, lets work out what position along the cell wall the
            // ray struck (disabled because it's not being used)
            //cellPos = MathFP.toInt(ixFP) % TILE_HEIGHT;
         }
         else
            // make sure we dont think this is the closest (otherwise it would
            // still be 0)
            horizDistanceFP = MathFP.toFP(99999);

         // --------------- VERTICAL RAY ------------------
         boolean gotVertHit = false;
         int vertDistanceFP = 0;

         // if the ray can possibly hit a vertical line
         if (rayAngle != 90 && rayAngle != 270)
         {
            // cast the first ray to the intersection point

            // figure out the coord of the vert tile line we're after
            // (based on whether we're looking left or right). Note we offset
            // by one pixel so we know we're *inside* a tile cell

            if (rayAngle < 90 || rayAngle > 270)   // if ray going right
               originXFP = MathFP.toFP((((startingX / TILE_WIDTH) +1) *
                                        TILE_WIDTH) + 1);
            else                             // if ray going left
               originXFP = MathFP.toFP(((startingX / TILE_WIDTH) *
                                        TILE_WIDTH) - 1);

            destinationXFP = MathFP.sub(originXFP, startingXFP);
            destinationYFP = MathFP.div(destinationXFP,
                                        lookupTanFP[angleChange(rayAngle,-90)]);
            originYFP = MathFP.add(startingYFP, destinationYFP);

            // get the distance to the first grid cell
            vertDistanceFP = getDistanceFP(destinationXFP, destinationYFP,
                                           rayAngle);

            while (!gotVertHit)
            {
               if (vertDistanceFP > HORIZON_DISTANCE_FP) break;

               // did we hit a wall?
               if (isWall(MathFP.toInt(originXFP), MathFP.toInt(originYFP)))
               {
                  gotVertHit = true;
                  break;
               }

               if (!isOnMap(MathFP.toInt(originXFP), MathFP.toInt(originYFP)))
                  break;

               int lastXFP = originXFP;
               int lastYFP = originYFP;

               // project to the next point along
               if (rayAngle < 90 || rayAngle > 270)   // if ray going right
                  originXFP = MathFP.add(lastXFP, TILE_WIDTH_FP);
               else
                  originXFP = MathFP.sub(lastXFP, TILE_WIDTH_FP);

               destinationXFP = MathFP.sub(originXFP, lastXFP);
               destinationYFP = MathFP.div(destinationXFP,
                                           lookupTanFP[angleChange(rayAngle,-90)]);
               originYFP = MathFP.add(lastYFP, destinationYFP);

               // extend out the distance (so we know when we're casting
               // beyond the world edge)
               vertDistanceFP = MathFP.add(vertDistanceFP, getDistanceFP(
                       destinationXFP, destinationYFP, rayAngle));
            }
         }

         if (gotVertHit)
         {
            // got a hit, lets work out what position along the cell wall the
            // ray struck
            //cellPos = MathFP.toInt(iyFP) % TILE_WIDTH;
         }
         else // make sure we dont think this is the closest
            vertDistanceFP = MathFP.toFP(99999);

         // -------------- DRAW WALL SLICE ------------------

         // since it's possible (especially with nearby walls) to get a ray
         // hit on both vertical and horizontal lines we have to figure out
         // which one to use (the closest)
         if (gotVertHit || gotHorizHit)
         {
            int distanceFP = MathFP.min(horizDistanceFP, vertDistanceFP);
            int diffFP = MathFP.abs(MathFP.sub(horizDistanceFP, vertDistanceFP));

            boolean wasVerticalHit = true;

            if (horizDistanceFP > vertDistanceFP)
               wasVerticalHit = false;

            if (diffFP <= EDGE_IGNORE_FP)
               // if distance is the same then we hit a corner, we assume the
               // previous dir hit so as to give us a smooth line along walls
               wasVerticalHit = lastHitWasVert;

            if (wasVerticalHit)
            {
               // VERTICAL EDGE
               if (diffFP > EDGE_IGNORE_FP) lastHitWasVert = true;
               g.setColor(0x777777);
            }
            else
            {
               // HORIZONTAL EDGE
               if (diffFP > EDGE_IGNORE_FP) lastHitWasVert = false;
               g.setColor(0x333333);
            }

            if (lookupDistortionFP[castColumn] > 0 && distanceFP > 0)
               // adjust for distortion
               distanceFP = MathFP.div(distanceFP, lookupDistortionFP[castColumn]);

            if (distanceFP > 0)
            {
               int wallHeight = MathFP.toInt(MathFP.div(projWallHeight, distanceFP));

               int bottomOfWall = PROJ_PLANE_HEIGHT_CENTER + (wallHeight/2);
               int topOfWall = PROJ_PLANE_HEIGHT - bottomOfWall;

               if (bottomOfWall >= PROJ_PLANE_HEIGHT)
                  bottomOfWall = PROJ_PLANE_HEIGHT-1;

               // draw the wall (pixel column)
               g.fillRect(pixelColumn, topOfWall, columnsPerDegree, wallHeight);
            }

            // and move across to the next column position
            pixelColumn += columnsPerDegree;
         }

      }

      //System.out.println("done ----------------------");
   }


}