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2D Continous Collision Detection in Monogame/Xna Framework

I'm working on a custom physics engine for a potential game - based in Monogame/the XNA framework. While the physics itself works pretty well, I'm running into an issue with collision. When the player comes out of a jump, they can often end up inside the floor.
See image below. I did a couple hours of research on my own and found out that what I probably need is continous collision detection (CCD) similar to how something like Unity might implement it, but all the questions I've found here or other places haven't really worked, and neither has any of my solutions, so I'm asking the strangers on the internet who are smarter than me.
Here's game 1:
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using MonoGame.Extended;
using AmethystDawn.Utilities;
namespace AmethystDawn
{
internal class Game1 : Game
{
Texture2D spritesheet;
Texture2D spritesheetFlipped;
Texture2D activeSpritesheet;
Texture2D platform;
float timer; // millisecond timer
int threshold;
Rectangle[] sourceRectangles;
byte previousAnimationIndex;
byte currentAnimationIndex;
RectangleF playerCollider;
RectangleF groundCollider;
PhysicsCalculator physics = new();
Vector2 PlayerPos = new Vector2(0, 0);
private GraphicsDeviceManager graphics;
private SpriteBatch sprites;
private SpriteFont font;
public Game1() : base()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
IsFixedTimeStep = true;
IsMouseVisible = true;
IsFixedTimeStep = false;
}
protected override void Initialize()
{
base.Initialize();
}
protected override void LoadContent()
{
graphics.PreferredBackBufferWidth = GraphicsDevice.DisplayMode.Width;
graphics.PreferredBackBufferHeight = GraphicsDevice.DisplayMode.Height;
graphics.IsFullScreen = true;
graphics.HardwareModeSwitch = false;
graphics.ApplyChanges();
sprites = new SpriteBatch(GraphicsDevice);
font = Content.Load<SpriteFont>("Fonts/november");
spritesheet = Content.Load<Texture2D>("Sprites/Player/player spritesheet");
spritesheetFlipped = Content.Load<Texture2D>("Sprites/Player/player spritesheet flipped");
platform = Content.Load<Texture2D>("Sprites/platform");
activeSpritesheet = spritesheet;
timer = 0;
threshold = 100;
sourceRectangles = new Rectangle[4];
sourceRectangles[0] = new Rectangle(0, 0, 32, 40);
sourceRectangles[1] = new Rectangle(34, 0, 28, 40);
sourceRectangles[2] = new Rectangle(66, 0, 28, 40);
sourceRectangles[3] = new Rectangle(96, 0, 32, 40);
previousAnimationIndex = 2;
currentAnimationIndex = 1;
base.LoadContent();
}
protected override void UnloadContent()
{
base.UnloadContent();
}
protected override void Update(GameTime gameTime)
{
if (timer > threshold) // check if the timer has exceeded the threshold
{
if (currentAnimationIndex == 1) // if sprite is in the middle sprite of the animation
{
if (previousAnimationIndex == 0) // if the previous animation was the left-side sprite, then the next animation should be the right-side sprite
{
currentAnimationIndex = 2;
}
else
{
currentAnimationIndex = 0; // if not, then the next animation should be the left-side sprite
}
previousAnimationIndex = currentAnimationIndex;
}
else
{
currentAnimationIndex = 1; // if not in the middle sprite of the animation, return to the middle sprite
}
timer = 0;
}
else
{
// if the timer has not reached the threshold, then add the milliseconds that have past since the last Update() to the timer
timer += (float)gameTime.ElapsedGameTime.TotalMilliseconds;
}
base.Update(gameTime);
}
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
sprites.Begin();
sprites.Draw(platform, new Vector2(0, GraphicsDevice.Viewport.Height - platform.Height - 50), Color.White);
groundCollider = new RectangleF(0, GraphicsDevice.Viewport.Height - platform.Height - 50, platform.Width, platform.Height);
var kstate = Keyboard.GetState();
playerCollider = new(PlayerPos.X, PlayerPos.Y, sourceRectangles[currentAnimationIndex].Width, sourceRectangles[currentAnimationIndex].Height);
if (IsColliding(groundCollider, playerCollider))
{
physics.UpdatePhysicValues(false);
/*if (PlayerPos.Y + playerCollider.Height + 100 > groundCollider.Y)
{
PlayerPos.Y = groundCollider.Y - groundCollider.Height;
}*/
if (kstate.IsKeyDown(Keys.Space))
{
physics.Jump(3f);
}
}
else
{
physics.UpdatePhysicValues(true);
if (kstate.IsKeyDown(Keys.Space))
{
physics.MidairJump(3f);
}
else
{
physics.LockJump();
}
}
if (kstate.IsKeyDown(Keys.A))
{
physics.ApplyWalkingForce(new Vector2(-1, 0), 0.5f);
activeSpritesheet = spritesheetFlipped;
sourceRectangles[0] = new Rectangle(0, 0, 32, 40);
sourceRectangles[1] = new Rectangle(34, 0, 28, 40);
sourceRectangles[2] = new Rectangle(66, 0, 28, 40);
sourceRectangles[3] = new Rectangle(96, 0, 32, 40);
}
else if (kstate.IsKeyDown(Keys.D))
{
physics.ApplyWalkingForce(new Vector2(1, 0), 0.5f);
activeSpritesheet = spritesheet;
sourceRectangles[0] = new Rectangle(96, 0, 32, 40);
sourceRectangles[1] = new Rectangle(66, 0, 28, 40);
sourceRectangles[2] = new Rectangle(34, 0, 28, 40);
sourceRectangles[3] = new Rectangle(0, 0, 32, 40);
}
else
{
}
if (kstate.IsKeyDown(Keys.S) && !IsColliding(groundCollider, playerCollider))
{
physics.ApplyExtraGravity(1f);
}
if (kstate.IsKeyDown(Keys.R))
{
PlayerPos = new Vector2(0, 0);
}
PlayerPos = physics.position(PlayerPos);
// is player on the bounds of the screen
if (PlayerPos.X < 0)
{
PlayerPos.X = 0;
physics.HitWall();
}
else if (PlayerPos.X > GraphicsDevice.Viewport.Width - 32)
{
PlayerPos.X = GraphicsDevice.Viewport.Width - 32;
physics.HitWall();
}
sprites.Draw(activeSpritesheet, PlayerPos, sourceRectangles[currentAnimationIndex], Color.White, 0f, new Vector2(0, 0), 1f, SpriteEffects.None, 0f);
sprites.End();
base.Draw(gameTime);
}
private bool IsColliding(RectangleF rect1, RectangleF rect2)
{
return rect1.Intersects(rect2);
}
}
}
And here's the physics calculator:
using System.Diagnostics;
using Microsoft.Xna.Framework;
namespace AmethystDawn.Utilities
{
internal class PhysicsCalculator
{
private float directionalForce;
private Vector2 direction;
private const float directionalForceMax = 10f;
private float walkingForce;
private const float walkingForceMax = 0.5f;
private float gravityForce;
private const float gravityForceMax = 25f;
private float jumpForce;
private const float jumpForceMax = 5f;
private int framesInAir;
private const int framesInAirMax = 90;
public void UpdatePhysicValues(bool falling)
{
if (directionalForce > 0)
{
directionalForce -= 0.5f;
}
if (walkingForce > 0)
{
walkingForce -= 0.02f;
}
else
{
walkingForce = 0;
}
if (gravityForce > jumpForce)
{
if (falling && !(gravityForce > gravityForceMax))
{
gravityForce += 0.2f;
}
else if (!falling)
{
gravityForce = 0;
direction.Y = 0;
framesInAir = 0;
}
}
else
{
jumpForce -= 0.3f;
}
FixDirection();
}
public void ApplyDirectionalForce(Vector2 directionHit, float forceToApply)
{
direction += directionHit;
directionalForce += forceToApply;
if (directionalForce > directionalForceMax) directionalForce = directionalForceMax;
}
public void ApplyWalkingForce(Vector2 directionWalked, float forceToApply)
{
direction += directionWalked;
walkingForce += forceToApply;
if (walkingForce > walkingForceMax) walkingForce = walkingForceMax;
}
public void Jump(float force)
{
direction += new Vector2(0, -1);
jumpForce += force;
if (jumpForce > jumpForceMax) jumpForce = jumpForceMax;
}
public void MidairJump(float force)
{
framesInAir++;
if (framesInAir > framesInAirMax) return;
jumpForce += force;
if (jumpForce > jumpForceMax) jumpForce = jumpForceMax;
}
public void LockJump()
{
framesInAir = framesInAirMax;
}
public void ApplyExtraGravity(float amount)
{
gravityForce += amount;
}
public Vector2 position(Vector2 currentPosition)
{
currentPosition += new Vector2(0, gravityForce);
currentPosition += new Vector2(direction.X * directionalForce, direction.Y * directionalForce);
currentPosition += new Vector2(direction.X * walkingForce, direction.Y * walkingForce);
currentPosition += new Vector2(0, direction.Y * jumpForce);
return currentPosition;
}
public void HitWall()
{
direction.X = 0;
}
private void CorrectGravity()
{
}
private void FixDirection()
{
if (direction.X > 20) direction.X = 20;
if (direction.Y > 20) direction.Y = 20;
if (direction.X < -20) direction.X = -20;
if (direction.Y < -15) direction.Y = -15;
if (walkingForce <= 0 && directionalForce <= 0) direction.X = 0;
}
}
}
And the image:

I remember watching a tutorial that explained the way of handling continious collision, but that was done in GameMaker Studio 2.
I'll try to translate it to XNA.
In short: You need to check for collision ahead of you with calculating the collision with the current speed beforehand, then let the player approach the solid object 1 pixel at a time through a while loop, and once it hits, then set the velocity in that direction to 0.
Original GMS2 code:
if place_meeting(x+hspeed_, y, o_solid) {
while !place_meeting(x+sign(hspeed_), y, o_solid) {
x += sign(hspeed_);
}
hspeed_ = 0;
}
x += hspeed_;
translated to XNA (dummy code as quick example):
private bool IsColliding(RectangleF rect1, RectangleF rect2, int vspeed)
{
if (rect1.Intersects(new Rectangle(rect2.x, rect2.y + vspeed, rect2.Width, rect2.Height))
{
while (!rect1.Intersects(new Rectangle(rect2.x, rect2.y+Sign(vspeed), rect2.Width, rect2.Height)
{
rect1 += Sign(vspeed) //moves towards the collision 1 pixel at a time
}
return true;
}
return false;
}
//Sign is a build-in function in GMS2 that only returns 1, 0 or -1, depending if the number is positive, 0 or negative
private int Sign(value)
{
return (value > 0) ? 1 : (value < 0) ? -1 : 0;
}
Source: https://youtu.be/zqtT_9eWIkM?list=PL9FzW-m48fn3Ya8QUTsqU-SU6-UGEqhx6

(Xna) My players position won't update, I need it for my enemy to follow

enter code hereWhen im drawing it to a string it just stays at 300,300 . My mouse always updates its Vector2 position.X, position.Y. I need to be able to update my players position or my enemy wont follow my player. It just goes to that certain player position i set for it. PLEASE HELP AND THANK YOU!
class Enemy
{
Player p = new Player();
public Vector2 direction, velocity,position;
public float speed;
public Texture2D texture;
public Enemy()
{
speed = 1;
texture = null;
position = new Vector2(600, 500);
}
public void LoadContent(ContentManager Content)
{
texture = Content.Load<Texture2D>("circle");
}
public void Update(GameTime gameTime)
{
MouseState mouse = Mouse.GetState();
direction = p.position - position;
direction.Normalize();
velocity = direction * speed;
position += velocity;
}
public void Draw(SpriteBatch spriteBatch)
{
spriteBatch.Draw(texture, position, Color.Red);
}
/*
direction = p.position - position;
direction.Normalize();
velocity = direction * speed;
position += velocity;
*/
}
class Player
{
public float rotation, bulletDelay;
public Vector2 position,velocity,origin;
public string spriteName;
public Texture2D texture,bulletTexture;
List<Bullets> bullets = new List<Bullets>();
public float speed = 10;
public float health = 100;
public Player()
{
texture = null;
spriteName = "playerover";
position = new Vector2(300, 300);
bulletDelay = 20;
}
public void LoadContent(ContentManager Content)
{
texture = Content.Load<Texture2D>(spriteName);
bulletTexture = Content.Load<Texture2D>("playerbullet");
}
public void Draw(SpriteBatch spriteBatch)
{
origin = new Vector2(texture.Width / 2, texture.Height / 2);
spriteBatch.Draw(texture, new Rectangle((int)position.X, (int)position.Y, texture.Width, texture.Height), null, Color.White, rotation,new Vector2(texture.Width / 2, texture.Height / 2), SpriteEffects.None, 0);
foreach (Bullets bullet in bullets)
{
bullet.Draw(spriteBatch);
}
}
public void Update(GameTime gameTime)
{
MouseState curMouse = Mouse.GetState();
KeyboardState keyState = Keyboard.GetState();
Vector2 mouseLoc = new Vector2(curMouse.X, curMouse.Y);
Vector2 direction = mouseLoc - position;
rotation = (float)(Math.Atan2(direction.Y, direction.X));
if (keyState.IsKeyDown(Keys.W))
{
position.Y -= speed;
}
if (keyState.IsKeyDown(Keys.S))
{
position.Y += speed;
}
if (keyState.IsKeyDown(Keys.A))
{
position.X -= speed;
}
if (keyState.IsKeyDown(Keys.D))
{
position.X += speed;
}
if (curMouse.LeftButton == ButtonState.Pressed)
{
Shoot();
}
UpdateBullets();
}
public void UpdateBullets()
{
foreach (Bullets bullet in bullets)
{
bullet.position += bullet.velocity;
if (bullet.position.Y <= 5)
{
bullet.isVisible = false;
}
if (bullet.position.X <= 5)
{
bullet.isVisible = false;
}
if (bullet.position.X >= 785)
{
bullet.isVisible = false;
}
if (bullet.position.Y >= 575)
{
bullet.isVisible = false;
}
}
for (int i = 0; i < bullets.Count; i++)
{
if (!bullets[i].isVisible)
{
bullets.RemoveAt(i);
i--;
}
}
}
public void Shoot()
{
if (bulletDelay >= 0)
bulletDelay--;
if (bulletDelay <= 0)
{
Bullets newBullet = new Bullets(bulletTexture);
newBullet.velocity = new Vector2((float)Math.Cos(rotation), (float)Math.Sin(rotation)) * 5f + velocity;
newBullet.position = position + newBullet.velocity * 5;
newBullet.isVisible = true;
if (bullets.Count < 20)
{
bullets.Add(newBullet);
}
}
if (bulletDelay == 0)
{
bulletDelay = 20;
}
}
}
class Hud
{
public SpriteFont font;
public bool showHud;
Player p = new Player();
Enemy e = new Enemy();
public Hud()
{
showHud = true;
}
public void LoadContent(ContentManager Content)
{
font = Content.Load<SpriteFont>("font");
}
public void Draw(SpriteBatch spriteBatch)
{
MouseState mouse = Mouse.GetState();
if (showHud)
{
spriteBatch.DrawString(font, "Mouse.X = " + mouse.X, new Vector2(10, 0), Color.White);
spriteBatch.DrawString(font, "Mouse.Y = " + mouse.Y, new Vector2(10, 20), Color.White);
spriteBatch.DrawString(font, "Health = " + p.health, new Vector2(10, 40), Color.White);
spriteBatch.DrawString(font, "Pos.Y = " + p.position.Y, new Vector2(10, 60), Color.White);
spriteBatch.DrawString(font, "Pos.X = " + p.position.X, new Vector2(10, 80), Color.White);
}
}
}

I didn't read all the code you posted, but it seems that you created a new separate instance for the player in the Enemy class which is never updated.
class Enemy
{
Player p = new Player();
//...
}
You should either take a Vector2 for the players position into your enemies Update method or handle the enemy movement somewhere else. Perhaps you could have a method in your Enemy class named Follow taking a Player object as a parameter, then you could do something like the following in the place where you handle all entity movement. It would look roughly like this:
public void UpdateEntities(GameTime gameTime)
{
player.Update(gameTime);
enemy.Update(gameTime);
if(PlayerDistanceFromEnemy() < 50)
enemy.Follow(player);
}
That is a very rough guideline and probably something you'd want to rewrite later on, but it will work.
as for the Follow method in your enemy class:
public void Follow(Player player)
{
this.p = player;
}
public void Update(GameTime gameTime)
{
if(p != null)
{
//do stuff
}
}
This will work, but you have to work on the structure of your code if you want to expand. I might update this answer later with a better solution if someone doesn't do it before me.

When implementing simple Pong AI, two paddles are created and flicker

So, me being a new programmer, instead doing actual AI implementation, I used the following solution for making paddle on the right follow the ball:
if(ball.position.Y > p2.position.Y)
{
p2.position.Y += ball.position.Y;
}
else if (ball.position.Y < p2.position.Y)
{
p2.position.Y -= ball.position.Y;
}
However this happens (okay I tried taking a screencap with PrtScn and it semmed to pause the game for a microsecond and capture a single paddle instead of two flickering ones)
So what can I do to make the paddle 2 appear as one?
Full Code of Program:
Game1.cs
namespace Pong
{
public class Game1 : Game
{
//Variables
GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
//Borders
Texture2D borders;
//Paddles
Paddle p1 = new Paddle();
Paddle p2 = new Paddle();
//Ball
Ball ball = new Ball();
//Positions
Vector2 bordersPos;
//Constructor
public Game1()
: base()
{
graphics = new GraphicsDeviceManager(this);
graphics.IsFullScreen = false;
graphics.PreferredBackBufferHeight = 800;
graphics.PreferredBackBufferWidth = 800;
//Content Loader
Content.RootDirectory = "Content";
}
//Initialize
protected override void Initialize()
{
base.Initialize();
}
//Load Content
protected override void LoadContent()
{
spriteBatch = new SpriteBatch(GraphicsDevice);
//Assigning Textures
p1.texture = Content.Load<Texture2D>("paddle1");
p2.texture = Content.Load<Texture2D>("paddle1");
borders = Content.Load<Texture2D>("borders");
ball.texture = Content.Load<Texture2D>("ball");
//Positions
p1.position.X = 50;
p1.position.Y = graphics.GraphicsDevice.Viewport.Height / 2 - (p1.height / 2);
p2.position.X = graphics.GraphicsDevice.Viewport.Width - 50 - p2.width;
p2.position.Y = graphics.GraphicsDevice.Viewport.Height / 2 - (p2.height / 2);
bordersPos.Y = 0;
bordersPos.X = 0;
ball.position.X = 800 / 2 - ball.width / 2;
ball.position.Y = 800 / 2 - ball.height / 2;
}
protected override void UnloadContent()
{
}
//Update
protected override void Update(GameTime gameTime)
{
//Exit
if (Keyboard.GetState().IsKeyDown(Keys.Escape))
Exit();
//Update Player Controls
PlayerInput();
p1.Update();
p2.Update();
ball.Update();
//Paddle Collision
if (padCol1())
{
if (ball.movingDownLeft)
{
ball.movingDownRight = true;
ball.movingDownLeft = false;
}
else if (ball.movingUpLeft)
{
ball.movingUpRight = true;
ball.movingUpLeft = false;
}
}
if (padCol2())
{
if (ball.movingDownRight)
{
ball.movingDownLeft = true;
ball.movingDownRight = false;
}
else if (ball.movingUpRight)
{
ball.movingUpLeft = true;
ball.movingUpRight = false;
}
}
//AI
if(ball.position.Y > p2.position.Y){
p2.position.Y += ball.position.Y;
}
else if (ball.position.Y < p2.position.Y)
{
p2.position.Y -= ball.position.Y;
}
base.Update(gameTime);
}
//Draw
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.Black);
spriteBatch.Begin(SpriteSortMode.BackToFront, BlendState.AlphaBlend);
//Paddles
p1.Draw(spriteBatch);
p2.Draw(spriteBatch);
//Borders
spriteBatch.Draw(borders, bordersPos, Color.White);
//Ball
ball.Draw(spriteBatch);
spriteBatch.End();
base.Draw(gameTime);
}
//Player Input
public void PlayerInput()
{
//Player 1
if (Keyboard.GetState(p1.pNumber).IsKeyDown(Keys.W))
{
p1.position.Y -= p1.speed;
}
else if (Keyboard.GetState(p1.pNumber).IsKeyDown(Keys.S))
{
p1.position.Y += p1.speed;
}
}
//Paddle Collision
public bool padCol1()
{
if (ball.position.Y >= p1.position.Y && ball.position.X > p1.position.X && ball.position.X < (p1.position.X + p1.width) && ball.position.Y < (p1.position.Y + p1.height))
{
return true;
}
else
return false;
}
public bool padCol2()
{
if (ball.position.Y >= p2.position.Y && ball.position.X > p2.position.X && ball.position.X < (p2.position.X + p2.width) && ball.position.Y < (p2.position.Y + p2.height))
{
return true;
}
else
return false;
}
}
}
Paddle.cs
namespace Pong
{
class Paddle : Game
{
//Variables
public Texture2D texture;
public Vector2 position;
public PlayerIndex pNumber;
public int width, height;
public float speed;
//Constructor
public Paddle()
{
texture = null;
position = Vector2.Zero;
pNumber = PlayerIndex.One;
width = 64;
height = 187;
speed = 10.0f;
}
//Update
public void Update()
{
//Set Boundaries
if (position.Y <= 30)
position.Y = 30;
if (position.Y >= 800 - 217)
position.Y = 800 - 217;
}
//Draw
public void Draw(SpriteBatch spriteBatch)
{
spriteBatch.Draw(texture, position, Color.White);
}
}
}
Ball.cs
namespace Pong
{
class Ball : Game
{
//Variables
public Vector2 position;
public Texture2D texture;
public int width, height;
public float speed;
public bool movingDownLeft, movingUpLeft, movingDownRight, movingUpRight;
//Constructor
public Ball()
{
Content.RootDirectory = ("Content");
speed = 6.0f;
width = 20;
height = 20;
movingDownLeft = true;
movingUpRight = false;
movingUpLeft = false;
movingDownRight = false;
position = Vector2.Zero;
}
//Draw
public void Draw(SpriteBatch spriteBatch)
{
spriteBatch.Draw(texture, position, Color.White);
}
//Update
public void Update()
{
//Directions
if(movingUpLeft){
position.Y -= speed;
position.X -= speed;
}
if (movingDownLeft)
{
position.Y += speed;
position.X -= speed;
}
if (movingUpRight)
{
position.Y -= speed;
position.X += speed;
}
if (movingDownRight)
{
position.Y += speed;
position.X += speed;
}
//Ball Wall Collision
if(movingUpLeft && position.Y <= 30)
{
movingDownLeft = true;
movingUpLeft = false;
}
//1
else if (movingDownLeft && position.X <= 0)
{
movingDownRight = true;
movingDownLeft = false;
}
//2
else if (movingUpLeft && position.X <= 0)
{
movingUpRight = true;
movingUpLeft = false;
}
//3
else if (movingDownLeft && position.Y >= 800 - 45)
{
movingUpLeft = true;
movingDownLeft = false;
}
//4
else if (movingDownRight && position.X >= 800 - width)
{
movingDownLeft = true;
movingDownRight = false;
}
//5
else if (movingUpRight && position.Y <= 30)
{
movingDownRight = true;
movingUpRight = false;
}
//6
else if (movingDownRight && position.Y >= 800 - 45)
{
movingUpRight = true;
movingDownRight = false;
}
//7
else if (movingUpRight && position.X >= 800 - width)
{
movingUpLeft = true;
movingUpRight = false;
}
}
}
}

I've never used MonoGame but this:
if(ball.position.Y > p2.position.Y)
{
p2.position.Y += ball.position.Y;
}
else if (ball.position.Y < p2.position.Y)
{
p2.position.Y -= ball.position.Y;
}
Will always overshoot, then trigger the next update.
Why don't you just do:
p2.position.Y = ball.position.Y;
EDIT: You should probably also make your input frame rate independent (unless MonoGame does this for you). It seems now you'll get higher movement speed on your paddles depending on your framerate.

Paddle and Game must not inherit from Game (GameComponent instead?). There should be only one Game object.
You should replace you booleans and complex logic with Vector2 speed describing speed of a ball, and negate its X or Y when the ball hits something.

Object reference is not set to an object

I am trying to create collision between my bullets and the enemy. I have created bounding boxes for each and placed them into their own class. However, I am getting a Null reference error in my HandleCollision function, specifically at the if statement with the bounding boxes. I will also post the rest of my code.
I discussed this with two lecturers and some peers and they asy it is because bullet and enemy are equal to null. This is because it takes a couple of seconds for the enemy to spawn and the bullet only spawns once it is fired. To counter this I added an if statement to check if the bullet or enemy is null yet it still throws up the same error.
HandleCollision Function
private void HandleCollision()//collision
{
Sprite toRemove = null;
if (bullet != null || enemyTexture != null)
{
foreach (EnemySprite e in enemyList) //checks each enemy sprite
{
if (bullet.BoundingBox.Intersects(enemy.BoundingBox))
{
enemyList.Remove(enemy); //removes enemy
//toRemove = enemy;
break;
}
}
}
}
Game1.cs
public class Game1 : Microsoft.Xna.Framework.Game
{
GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
Rectangle spriteRectangle;
Rectangle bulletBounds;
Rectangle enemyBounds;
Sprite player;
Bullets bullet;
EnemySprite enemy;
Texture2D enemyTexture;
List<EnemySprite> enemyList = new List<EnemySprite>();
List<Bullets> bulletsList = new List<Bullets>();
//Pause
bool paused = false;
Texture2D pauseTexture;
Rectangle pauseRectangle;
KeyboardState pastKey;
Vector2 enemyPos = new Vector2(100, 400);
Vector2 Position;
Vector2 Distance;
Vector2 spriteOrigin;
Vector2 spriteVelocity;
const float tangentialVelocity = 5f;
float friction = 0.1f;
float rotation;
float timer = 0f;
float dropInterval = 2f;
float speed = 4f;
float angle;
Random random;
enum GameState
{
MainMenu,
Options,
Help,
Playing,
Exit,
}
GameState CurrentGameState = GameState.MainMenu;
// Screen adjustments
int screenWidth = 800, screenHeight = 600;
cButton btnPlay;
cButtonExit btnExit;
public Game1()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
}
protected override void Initialize()
{
// TODO: Add your initialization logic here
random = new Random();
Position = new Vector2(150, 150);
this.IsMouseVisible = true;
base.Initialize();
}
protected override void LoadContent()
{
// Create a new SpriteBatch, which can be used to draw textures.
spriteBatch = new SpriteBatch(GraphicsDevice);
player = new Sprite();
player.Texture = Content.Load<Texture2D>("graphics/player");
// Screen stuff
graphics.PreferredBackBufferWidth = screenWidth;
graphics.PreferredBackBufferHeight = screenHeight;
//graphics.IsFullScreen = true;
graphics.ApplyChanges();
IsMouseVisible = true;
btnPlay = new cButton(Content.Load<Texture2D>("Graphics/play"), graphics.GraphicsDevice);
btnPlay.setPosition(new Vector2(350, 190));
btnExit = new cButtonExit(Content.Load <Texture2D>("Graphics/exit"), graphics.GraphicsDevice);
btnExit.setPosition(new Vector2(350, 220));
enemyTexture = Content.Load<Texture2D>("graphics/enemy");
player.Texture = Content.Load<Texture2D>("Graphics/player");
int screenCenterX = GraphicsDevice.Viewport.Width / 2;
player.Position = new Vector2(screenCenterX - (player.Texture.Width / 2), screenHeight - player.Texture.Height - 20);
pauseTexture = Content.Load<Texture2D>("graphics/paused");
pauseRectangle = new Rectangle(0, 0, pauseTexture.Width, pauseTexture.Height);
Bullets.BulletTexture = Content.Load<Texture2D>("graphics/bullet");
}
protected override void Update(GameTime gameTime)
{
MouseState mouse = Mouse.GetState();
IsMouseVisible = true;
switch (CurrentGameState)
{
case GameState.MainMenu:
if (btnPlay.isClicked == true) CurrentGameState = GameState.Playing;
btnPlay.Update(mouse);
if (btnExit.isClicked == true) CurrentGameState = GameState.Help;
btnExit.Update(mouse);
if (btnExit.isClicked == true) CurrentGameState = GameState.Options;
btnExit.Update(mouse);
if (btnExit.isClicked == true) CurrentGameState = GameState.Exit;
btnExit.Update(mouse);
break;
case GameState.Playing:
timer += (float)gameTime.ElapsedGameTime.TotalSeconds;
if (timer >= dropInterval)
{
int yPos = random.Next(GraphicsDevice.Viewport.Height - 50);
enemyList.Add(new EnemySprite(enemyTexture, new Vector2(GraphicsDevice.Viewport.Width + 100, yPos)));
timer = 0f;
}
HandleCollision();
HandleMovingEnemy();
MouseState curMouse = Mouse.GetState();
Vector2 mouseLoc = new Vector2(curMouse.X, curMouse.Y);
Vector2 direction = mouseLoc - Position;
spriteRectangle = new Rectangle((int)Position.X, (int)Position.Y,
player.Texture.Width, player.Texture.Height);
Position = spriteVelocity + Position;
spriteOrigin = new Vector2(spriteRectangle.Width / 2, spriteRectangle.Height / 2);
Distance.X = mouse.X - Position.X;
Distance.Y = mouse.Y - Position.Y;
rotation = (float)Math.Atan2(Distance.Y, Distance.X); //calculates the rotation(trigonometry)
//angle = (float)(Math.Atan2(direction.Y, direction.X));
KeyboardState keyState = Keyboard.GetState();
if (keyState.IsKeyDown(Keys.A))
Position.X -= 2;
if (keyState.IsKeyDown(Keys.D))
Position.X += 2;
if (keyState.IsKeyDown(Keys.W))
Position.Y -= 2;
if (keyState.IsKeyDown(Keys.S))
Position.Y += 2;
//right and left edge detection
if (Position.X < 0)
Position = new Vector2(0, Position.Y);
int rightEdge = GraphicsDevice.Viewport.Width - player.Texture.Width;
if (Position.X > rightEdge)
Position = new Vector2(rightEdge, Position.Y);
//bottom and top edge detection
if (Position.Y < 0)
Position = new Vector2(Position.X, 0);
int bottomEdge = GraphicsDevice.Viewport.Height - player.Texture.Height;
if (Position.Y > bottomEdge)
Position = new Vector2(Position.X, bottomEdge);
if (!paused)
{
if (Keyboard.GetState().IsKeyDown(Keys.Escape))
{
paused = true;
btnPlay.isClicked = false; //so that everytime its paused I can pause it again
}
enemy.Update();
}
else if(paused)
{
if (btnPlay.isClicked)
{
paused = false;
speed = 4;
}
if (btnExit.isClicked)
Exit();
btnPlay.Update(mouse);
btnExit.Update(mouse);
}
if (Keyboard.GetState().IsKeyDown(Keys.C))
{
spriteVelocity.X = (float)Math.Cos(rotation) * tangentialVelocity;
spriteVelocity.Y = (float)Math.Sin(rotation) * tangentialVelocity;
}
else if (spriteVelocity != Vector2.Zero)
{
float i = spriteVelocity.X;
float j = spriteVelocity.Y;
spriteVelocity.X = i -= friction * i;
spriteVelocity.Y = j -= friction * j;
}
if (Keyboard.GetState().IsKeyDown(Keys.Space) && pastKey.IsKeyUp(Keys.Space))
Fire();
pastKey = Keyboard.GetState();
UpdateBullets();
break;
case GameState.Exit:
this.Exit();
break;
}
base.Update(gameTime);
}
public void UpdateBullets()
{
foreach (Bullets bullet in bulletsList)
{
bullet.position += bullet.velocity;
if(Vector2.Distance(bullet.position, Position) > 500) //finds position
bullet.isVisible = false;
}
for (int i = 0; i < bulletsList.Count; i++)
{
if (!bulletsList[i].isVisible)
{
bulletsList.RemoveAt(i);
i--;
}
}
}
//function to handle movement of enemies
private void HandleMovingEnemy()
{
List<EnemySprite> toRemove = new List<EnemySprite>();
foreach (EnemySprite e in enemyList)
{
if (e.Position.X < (-20))
{
toRemove.Add(e);
}
else
e.Position -= new Vector2(speed, 0);
}
if (toRemove.Count > 0)
{
foreach (EnemySprite e in toRemove)
{
enemyList.Remove(e);
}
}
}
private void HandleCollision()//collision
{
Sprite toRemove = null;
if (bullet != null || enemyTexture != null)
{
foreach (EnemySprite e in enemyList) //checks each enemy sprite
{
if (bullet.BoundingBox.Intersects(enemy.BoundingBox)) //checks if a sprite has intersected an enemy
{
enemyList.Remove(enemy); //removes enemy
//toRemove = enemy;
break;
}
}
}
}
public void Fire()
{
Bullets newBullet = new Bullets(Content.Load<Texture2D>("graphics/bullet"));
Bullets.BulletTexture = Content.Load<Texture2D>("graphics/bullet");
//newBullet.LoadContent(LoadContent);
newBullet.velocity = new Vector2((float)Math.Cos(rotation), (float)Math.Sin(rotation)) * 5f + spriteVelocity;
newBullet.position = Position + newBullet.velocity * 5;
newBullet.isVisible = true;
if (bulletsList.Count() < 20)
bulletsList.Add(newBullet);
}
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
spriteBatch.Begin();
switch (CurrentGameState)
{
case GameState.MainMenu:
spriteBatch.Draw(Content.Load<Texture2D>("Graphics/SeaSideDefenderMainMenu"), new Rectangle(0,0,screenWidth,screenHeight),Color.White);
btnPlay.Draw(spriteBatch);
btnExit.Draw(spriteBatch);
break;
case GameState.Playing:
spriteBatch.Draw(Content.Load<Texture2D>("Graphics/leveltest"), new Rectangle(0, 0, screenWidth, screenHeight), Color.White);
enemy = new EnemySprite();
enemy.Texture = Content.Load<Texture2D>("graphics/enemy");
enemy.Draw(spriteBatch);
spriteBatch.Draw(player.Texture, Position, null, Color.White, rotation, spriteOrigin, 1f, SpriteEffects.None, 0);
//player.Draw(spriteBatch);
foreach (EnemySprite e in enemyList)
{
e.Draw(spriteBatch);
}
foreach (Bullets bullet in bulletsList)
bullet.draw(spriteBatch);
/*for (int i; i < enemyList.Count; i++)
{
enemyList[i].Draw(spriteBatch);
}*/
if (paused)
{
speed = 0;
spriteBatch.Draw(Content.Load<Texture2D>("graphics/paused"), new Rectangle(0, 0, screenWidth, screenHeight), Color.White);
btnPlay.Draw(spriteBatch);
btnExit.Draw(spriteBatch);
}
break;
}
spriteBatch.End();
base.Draw(gameTime);
}
}
Bullets.cs
public class Bullets
{
public Texture2D texture;
public static Texture2D BulletTexture;
public Vector2 position;
public Vector2 velocity;
public Vector2 origin;
public bool isVisible;
public Rectangle BoundingBox
{
get { return new Rectangle((int)position.X, (int)position.Y, texture.Width, texture.Height); }
}
public Bullets(Texture2D newTexture)
{
texture = newTexture;
isVisible = false;
}
public void draw(SpriteBatch spriteBatch)
{
spriteBatch.Draw(texture,position,null,Color.White,0f,origin,1f, SpriteEffects.None, 0);
}
public void LoadContent(ContentManager Content)
{
BulletTexture = Content.Load<Texture2D>(#"graphics/bullet");
}
}
enemy.cs
public class EnemySprite
{
public Texture2D Texture { get; set; }
public Vector2 Position {get; set; }
public Vector2 origin;
public Vector2 velocity;
public Rectangle rectangle;
float rotation = 0f;
bool right;
float distance;
float oldDistance;
public Rectangle BoundingBox
{
get { return new Rectangle((int)Position.X, (int)Position.Y, Texture.Width, Texture.Height); } //uses enemy position and wiwdth to create bounding box
}
public EnemySprite() { }
public EnemySprite(Texture2D texture, Vector2 position)
{
Texture = texture;
Position = position;
oldDistance = distance;
}
float mouseDistance;
public void Update()
{
Position += velocity;
origin = new Vector2(Texture.Width / 2, Texture.Height / 2);
if (distance <= 0)
{
right = true;
velocity.X = 1f;
}
else if(distance <= oldDistance)
{
right = false;
velocity.X = -1f;
}
if (right) distance += 1; else distance -= 1;
MouseState mouse = Mouse.GetState();
mouseDistance = mouse.X - Position.X;
if (mouseDistance >= -200 && mouseDistance <= 200)
{
if (mouseDistance < -1)
velocity.X = -1f;
else if (mouseDistance > 1)
velocity.X = 1f;
else if (mouseDistance == 0)
velocity.X = 0f;
}
}
public void Draw(SpriteBatch spriteBatch)
{
if (Texture != null)
spriteBatch.Draw(Texture, Position, Color.White);
if (velocity.X > 0)
{
spriteBatch.Draw(Texture, Position, null, Color.White, rotation, origin, 1f, SpriteEffects.FlipHorizontally, 0f);
}
else
{
spriteBatch.Draw(Texture, Position, null, Color.White, rotation, origin, 1f, SpriteEffects.None, 0f);
}
}
}

You've not initialized the global variable Bullet anywhere in your game1.cs, therefore you would never get bullet != null as true. Whereas, you'll always get enemyTexture != null as true since you've already initialized enemyTexture in the LoadContent().
Which means you'll always enter the if block while having the Bullet variable not initialized.
Hope this will lead you to the solution.
PS: Do mark the answer as 'Accepted' if this was the most helpful one.

Jumping animation

stayI need to make an animation while my sprite is jumping. I tried to load an animation if a key is pressed but it doesn't function. I jump by pressing Space key. All others animations function. So, my problem is to load an animation by pressing a key. I think I could use GameTime.Elapsed.TotalMilliseconds but I am not sure. I am new anyway and it is my first game.
class Player
{
PlayerAnimation animation;
Animation walk;
Animation stay;
Animation jump;;
public Vector2 position;
public Vector2 velocity;
public Rectangle rect;
public bool jumping = false;
public int health = 5;
public Vector2 Position{ get { return position; } }
public Player() { }
public void Load(ContentManager Content) {
walk = new Animation(Content.Load<Texture2D>("walk"), 46, 0.1f, true, rect);
animazioneMinima = new Animation(Content.Load<Texture2D>("stay"),37, 0.15f, true, rect);
jump = new Animation(Content.Load<Texture2D>("jump"), 51, 0.1f, true , rect);
}
public void Update(GameTime gameTime)
{
position += velocity;
rect = new Rectangle((int)position.X, (int)position.Y, 43, 46);
Input(gameTime);
if (velocity.X != 0)
PlayerAnimation.PlayAnimation(walk);
else if (velocity.X == 0)
PlayerAnimation.PlayAnimation(stay;
if (velocity.Y < 10)
velocity.Y += 0.4f;
}
private void Input(GameTime gameTime)
{
if (Keyboard.GetState().IsKeyDown(Keys.D))
velocity.X = (float)gameTime.ElapsedGameTime.TotalMilliseconds / 3;
else if (Keyboard.GetState().IsKeyDown(Keys.A))
velocity.X = -(float)gameTime.ElapsedGameTime.TotalMilliseconds / 3;
else velocity.X = 0f;
if (Keyboard.GetState().IsKeyDown(Keys.Space) && jumping == false)
{
position.Y -= 5f;
velocity.Y = -9f;
jumping = true;
}
}
public void Draw(GameTime gameTime, SpriteBatch spriteBatch)
{
SpriteEffects rotate = SpriteEffects.None;
if (velocity.X >= 0)
rotate = SpriteEffects.None;
else if (velocity.X < 0)
rotate = SpriteEffects.FlipHorizontally;
PlayerAnimation.Draw(gameTime, spriteBatch, position, rotate);
}
}
}
what should i make? :D

I don't know exactly how your code works, but maybe yau can write something like:
if (velocity.Y != 0)
{
PlayerAnimation.PlayAnimation(jump);
velocity.Y -= 0.05f
}
and insted of:
if (Keyboard.GetState().IsKeyDown(Keys.Space) && jumping == false)`
you can write:
if (Keyboard.GetState().IsKeyDown(Keys.Space) && velocity.Y == 0)
then you can skip using the jump bool completely.