Hello, I$\text{'}$m coding a simple tanks game in Java and and trying to draw, render and smooth the terrain from reading from a text file where X denotes the height of the terrain, T is the trees, and alphabet letters are the tanks default positions. The $2$nd image is what my code currently outputs but i need the terrain to be smoothed accordingly as it shows in the first image. Here's my current code, could you please help me smooth my current terrains so it looks like the output in the first image? Thank you.

Current Code App.java

package Tanks;

import org.checkerframework.checker.units.qual.A;

import processing.core.PApplet;

import processing.core.PImage;

import processing.data.JSONArray;

import processing.data.JSONObject;

import processing.event.KeyEvent;

import processing.event.MouseEvent;

import java.io$.$BufferedReader;

import java.io$.$FileReader;

import java.io$.$IOException;

import java.awt.$*$;

import java.awt.geom.AffineTransform;

import java.awt.image.BufferedImage;

import java.io$.*$;

import java.util.$*$;

public class App extends PApplet $\{$

public static final int CELLSIZE $=32$; $//8$;

public static final int CELLHEIGHT $=32$;

public static final int CELLAVG $=32$;

public static final int TOPBAR $=0$;

public static int WIDTH $=864$; $//$CELLSIZE$*$BOARD$\_$WIDTH;

public static int HEIGHT $=640$; $//$BOARD$\_$HEIGHT$*$CELLSIZE$+$TOPBAR;

public static final int BOARD$\_$WIDTH $=$ WIDTH$/$CELLSIZE;

public static final int BOARD$\_$HEIGHT $=20$;

public static final int INITIAL$\_$PARACHUTES $=1$;

public static final int FPS $=30$;

public String configPath;

public static Random random $=$ new Random$()$;

$//$ Feel free to add any additional methods or attributes you want. Please put classes in different files.

public App$()\{$

this.configPath $=$ "config.json";

$\}$

$/**$

$*$ Initialise the setting of the window size.

$*/$

@Override

public void settings$()\{$

size$($WIDTH$,$ HEIGHT$)$;

$\}$

$/**$

$*$ Load all resources such as images. Initialise the elements such as the player and map elements.

$*/$

PImage desertImage;

PImage forestImage;

PImage snowImage;

PImage treeOneImage;

PImage treeTwoImage;

@Override

public void setup$()\{$

size$($WIDTH$,$ HEIGHT$)$;

terrainHeights $=$ new float$[$BOARD$\_$WIDTH$]$;

Arrays.fill$($terrainHeights$,$ HEIGHT$)$;

frameRate$($FPS$)$;

desertImage $=$ loadImage$($getClass$().$getResource$("/$Tanks$/$desert$.$png$").$getPath$())$;

forestImage $=$ loadImage$($getClass$().$getResource$("/$Tanks$/$forest$.$png$").$getPath$())$;

snowImage $=$ loadImage$($getClass$().$getResource$("/$Tanks$/$snow$.$png$").$getPath$())$;

treeOneImage $=$ loadImage$($getClass$().$getResource$("/$Tanks$/$tree$1.$png$").$getPath$())$;

treeTwoImage $=$ loadImage$($getClass$().$getResource$("/$Tanks$/$tree$2.$png$").$getPath$())$;

try $\{$

BufferedReader reader $=$ new BufferedReader$($new FileReader$("$level$1.$txt$"))$;

String line;

int lineCount $=0$;

ArrayList lines $=$ new ArrayList;

while $(($line $=$ reader.readLine$())!=$ null$)\{$

lines.add$($line$)$; $//$ Collect all lines to process from top to bottom

$\}$

$//$ Process lines from bottom to top

for $($int y $=$ lines.size$()-1$; y $>=0$; y$--)\{$

line $=$ lines.get$($y$)$;

for $($int x $=0$; x $$ Math.min$($line$.$length$(),$ BOARD$\_$WIDTH$)$; x$++)\{$

if $($line$.$charAt$($x$)==\text{'}$X$\text{'})\{$

terrainHeights$[$x$]=$ HEIGHT $-($lines$.$size$()-$ y$)*$ CELLHEIGHT $+2*$CELLHEIGHT;

$\}$

$\}$

$\}$

reader.close$()$;

$\}$ catch $($IOException e$)\{$

e$.$printStackTrace$()$;

$\}$

$//$See PApplet javadoc:

$//$loadJSONObject$($configPath$)$

$//$loadImage$($this$.$getClass$().$getResource$($filename$).$getPath$().$toLowerCase$($Locale$.$ROOT$).$replace$("\%20",""))$;

$\}$

$/**$

$*$ Receive key pressed signal from the keyboard.

$*/$

@Override

public void keyPressed$($KeyEvent event$)\{$

$\}$

$/**$

$*$ Receive key released signal from the keyboard.

$*/$

@Override

public void keyReleased$()\{$

$\}$

@Override

public void mousePressed$($MouseEvent e$)\{$

$//$TODO $-$ powerups, like repair and extra fuel and teleport

$\}$

@Override

public void mouseReleased$($MouseEvent e$)\{$

$\}$

float$[]$ terrainHeights;

$/**$

$*$ Draw all elements in the game by current frame.

$*/$

@Override

public void draw$()\{$

image$($snowImage$,0,0,$ WIDTH, HEIGHT$)$;

fill$(255)$; $//$ snow white color of this terrain

noStroke$()$;

beginShape$()$;

vertex$(0,$ HEIGHT$)$; $//$ Start at bottom left

for $($int x $=0$; x $$ BOARD$\_$WIDTH; x$++)\{$

vertex$($x $*$ CELLSIZE, terrainHeights$[$x$])$;