How do I make a jumping dolphin rotate realistically?
- by Johnny
I want to program a dolphin that jumps and rotates like a real dolphin. Jumping is not the problem, but I don't know how to make the rotation. At the moment, my dolphin rotates a little weird. But I want that it rotates like a real dolphin does.
How can I improve the rotation?
public class Game1 : Microsoft.Xna.Framework.Game
{
GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
Texture2D image, water;
float Gravity = 5.0F;
float Acceleration = 20.0F;
Vector2 Position = new Vector2(1200,720);
Vector2 Velocity;
float rotation = 0;
SpriteEffects flip;
Vector2 Speed = new Vector2(0, 0);
public Game1()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
graphics.PreferredBackBufferWidth = 1280;
graphics.PreferredBackBufferHeight = 720;
}
protected override void Initialize()
{
base.Initialize();
}
protected override void LoadContent()
{
spriteBatch = new SpriteBatch(GraphicsDevice);
image = Content.Load<Texture2D>("cartoondolphin");
water = Content.Load<Texture2D>("background");
flip = SpriteEffects.None;
}
protected override void Update(GameTime gameTime)
{
float VelocityX = 0f;
float VelocityY = 0f;
float time = (float)gameTime.ElapsedGameTime.TotalSeconds;
KeyboardState kbState = Keyboard.GetState();
if(kbState.IsKeyDown(Keys.Left))
{
rotation = 0;
flip = SpriteEffects.None;
VelocityX += -5f;
}
if(kbState.IsKeyDown(Keys.Right))
{
rotation = 0;
flip = SpriteEffects.FlipHorizontally;
VelocityX += 5f;
}
// jump if the dolphin is under water
if(Position.Y >= 670)
{
if (kbState.IsKeyDown(Keys.A))
{
if (flip == SpriteEffects.None)
{
rotation += 0.01f;
VelocityY += 40f;
}
else
{
rotation -= 0.01f;
VelocityY += 40f;
}
}
}
else
{
if (flip == SpriteEffects.None)
{
rotation -= 0.01f;
VelocityY += -10f;
}
else
{
rotation += 0.01f;
VelocityY += -10f;
}
}
float deltaY = 0;
float deltaX = 0;
deltaY = Gravity * (float)gameTime.ElapsedGameTime.TotalSeconds;
deltaX += VelocityX * (float)gameTime.ElapsedGameTime.TotalSeconds * Acceleration;
deltaY += -VelocityY * (float)gameTime.ElapsedGameTime.TotalSeconds * Acceleration;
Speed = new Vector2(Speed.X + deltaX, Speed.Y + deltaY);
Position += Speed * (float)gameTime.ElapsedGameTime.TotalSeconds;
Velocity.X = 0;
if (Position.Y + image.Height/2 > graphics.PreferredBackBufferHeight)
Position.Y = graphics.PreferredBackBufferHeight - image.Height/2;
base.Update(gameTime);
}
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
spriteBatch.Begin();
spriteBatch.Draw(water, new Rectangle(0, graphics.PreferredBackBufferHeight -100, graphics.PreferredBackBufferWidth, 100), Color.White);
spriteBatch.Draw(image, Position, null, Color.White, rotation, new Vector2(image.Width / 2, image.Height / 2), 1, flip, 1);
spriteBatch.End();
base.Draw(gameTime);
}
}
I changed my code a little. But I still have some trouble with the rotation.
Here's the entire code.
The dolphin looks at the wrong direction if I press the left or right key. For example, it looks down if I press the left key.
What is wrong with the rotation? At the beginning, the dolphin looks at the left side, but after I pressed a key it just looks down or up.
I deleted the "rotation += 0.01f;" lines in the code. Is that correct?
public class Game1 : Microsoft.Xna.Framework.Game
{
GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
Texture2D image, water;
float Gravity = 5.0F;
float Acceleration = 20.0F;
Vector2 Position = new Vector2(1200,720);
Vector2 Velocity;
float rotation = 0;
SpriteEffects flip;
Vector2 Speed = new Vector2(0, 0);
Vector2 prevPos;
public Game1()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
graphics.PreferredBackBufferWidth = 1280;
graphics.PreferredBackBufferHeight = 720;
}
protected override void Initialize()
{
base.Initialize();
}
protected override void LoadContent()
{
spriteBatch = new SpriteBatch(GraphicsDevice);
image = Content.Load<Texture2D>("cartoondolphin");
water = Content.Load<Texture2D>("background");
flip = SpriteEffects.None;
}
protected override void Update(GameTime gameTime)
{
float VelocityX = 0f;
float VelocityY = 0f;
float time = (float)gameTime.ElapsedGameTime.TotalSeconds;
KeyboardState kbState = Keyboard.GetState();
if(kbState.IsKeyDown(Keys.Left))
{
flip = SpriteEffects.None;
VelocityX += -5f;
}
if(kbState.IsKeyDown(Keys.Right))
{
flip = SpriteEffects.FlipHorizontally;
VelocityX += 5f;
}
rotation = (float)Math.Atan2(Position.X - prevPos.X, Position.Y - prevPos.Y);
prevPos = Position;
// jump if the dolphin is under water
if(Position.Y >= 670)
{
if (kbState.IsKeyDown(Keys.A))
{
if (flip == SpriteEffects.None)
{
VelocityY += 40f;
}
else
{
VelocityY += 40f;
}
}
}
else
{
if (flip == SpriteEffects.None)
{
VelocityY += -10f;
}
else
{
VelocityY += -10f;
}
}
float deltaY = 0;
float deltaX = 0;
deltaY = Gravity * (float)gameTime.ElapsedGameTime.TotalSeconds;
deltaX += VelocityX * (float)gameTime.ElapsedGameTime.TotalSeconds * Acceleration;
deltaY += -VelocityY * (float)gameTime.ElapsedGameTime.TotalSeconds * Acceleration;
Speed = new Vector2(Speed.X + deltaX, Speed.Y + deltaY);
Position += Speed * (float)gameTime.ElapsedGameTime.TotalSeconds;
Velocity.X = 0;
if (Position.Y + image.Height/2 > graphics.PreferredBackBufferHeight)
Position.Y = graphics.PreferredBackBufferHeight - image.Height/2;
base.Update(gameTime);
}
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
spriteBatch.Begin();
spriteBatch.Draw(water, new Rectangle(0, graphics.PreferredBackBufferHeight -100, graphics.PreferredBackBufferWidth, 100), Color.White);
spriteBatch.Draw(image, Position, null, Color.White, rotation, new Vector2(image.Width / 2, image.Height / 2), 1, flip, 1);
spriteBatch.End();
base.Draw(gameTime);
}
}
