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I am creating a 2D XNA game and came across a tutorial on adding water effects (splashes) to an XNA game but after implementing it into my game I can't get it to scale down. Currently it takes up the entire screen.

The Water class looks like this

class Water
{
    struct WaterColumn
    {
        public float TargetHeight;
        public float Height;
        public float Speed;

        public void Update(float dampening, float tension)
        {
            float x = TargetHeight - Height;
            Speed += tension * x - Speed * dampening;
            Height += Speed;
        }
    }

    PrimitiveBatch pb;
    WaterColumn[] columns = new WaterColumn[201];
    static Random rand = new Random();

    public float Tension = 0.025f;
    public float Dampening = 0.025f;
    public float Spread = 0.25f;

    RenderTarget2D metaballTarget, particlesTarget;
    SpriteBatch spriteBatch;
    AlphaTestEffect alphaTest;
    Texture2D particleTexture;

    private float Scale { get { return spriteBatch.GraphicsDevice.Viewport.Width / (columns.Length - 1f); } }

    List<Particle> particles = new List<Particle>();
    class Particle
    {
        public Vector2 Position;
        public Vector2 Velocity;
        public float Orientation;

        public Particle(Vector2 position, Vector2 velocity, float orientation)
        {
            Position = position;
            Velocity = velocity;
            Orientation = orientation;
        }
    }

    public Water(GraphicsDevice device, Texture2D particleTexture)
    {
        pb = new PrimitiveBatch(device);
        this.particleTexture = particleTexture;
        spriteBatch = new SpriteBatch(device);
        metaballTarget = new RenderTarget2D(device, device.Viewport.Width, device.Viewport.Height);
        particlesTarget = new RenderTarget2D(device, device.Viewport.Width, device.Viewport.Height);
        alphaTest = new AlphaTestEffect(device);
        alphaTest.ReferenceAlpha = 175;

        var view = device.Viewport;
        alphaTest.Projection = Matrix.CreateTranslation(-0.5f, -0.5f, 0) *
            Matrix.CreateOrthographicOffCenter(0, view.Width, view.Height, 0, 0, 1);

        for (int i = 0; i < columns.Length; i++)
        {
            columns[i] = new WaterColumn()
            {
                Height = 240,
                TargetHeight = 240,
                Speed = 0
            };
        }
    }

    // Returns the height of the water at a given x coordinate.
    public float GetHeight(float x)
    {
        if (x < 0 || x > 800)
            return 240;

        return columns[(int)(x / Scale)].Height;
    }

    void UpdateParticle(Particle particle)
    {
        const float Gravity = 0.3f;
        particle.Velocity.Y += Gravity;
        particle.Position += particle.Velocity;
        particle.Orientation = GetAngle(particle.Velocity);
    }

    public void Splash(float xPosition, float speed)
    {
        int index = (int)MathHelper.Clamp(xPosition / Scale, 0, columns.Length - 1);
        for (int i = Math.Max(0, index - 0); i < Math.Min(columns.Length - 1, index + 1); i++)
            columns[index].Speed = speed;

        CreateSplashParticles(xPosition, speed);
    }

    private void CreateSplashParticles(float xPosition, float speed)
    {
        float y = GetHeight(xPosition);

        if (speed > 120)
        {
            for (int i = 0; i < speed / 8; i++)
            {
                Vector2 pos = new Vector2(xPosition, y) + GetRandomVector2(40);
                Vector2 vel = FromPolar(MathHelper.ToRadians(GetRandomFloat(-150, -30)), GetRandomFloat(0, 0.5f * (float)Math.Sqrt(speed)));
                CreateParticle(pos, vel);
            }
        }
    }

    private void CreateParticle(Vector2 pos, Vector2 velocity)
    {
        particles.Add(new Particle(pos, velocity, 0));
    }

    private Vector2 FromPolar(float angle, float magnitude)
    {
        return magnitude * new Vector2((float)Math.Cos(angle), (float)Math.Sin(angle));
    }

    private float GetRandomFloat(float min, float max)
    {
        return (float)rand.NextDouble() * (max - min) + min;
    }

    private Vector2 GetRandomVector2(float maxLength)
    {
        return FromPolar(GetRandomFloat(-MathHelper.Pi, MathHelper.Pi), GetRandomFloat(0, maxLength));
    }

    private float GetAngle(Vector2 vector)
    {
        return (float)Math.Atan2(vector.Y, vector.X);
    }

    public void Update()
    {
        for (int i = 0; i < columns.Length; i++)
            columns[i].Update(Dampening, Tension);

        float[] lDeltas = new float[columns.Length];
        float[] rDeltas = new float[columns.Length];

        // do some passes where columns pull on their neighbours
        for (int j = 0; j < 8; j++)
        {
            for (int i = 0; i < columns.Length; i++)
            {
                if (i > 0)
                {
                    lDeltas[i] = Spread * (columns[i].Height - columns[i - 1].Height);
                    columns[i - 1].Speed += lDeltas[i];
                }
                if (i < columns.Length - 1)
                {
                    rDeltas[i] = Spread * (columns[i].Height - columns[i + 1].Height);
                    columns[i + 1].Speed += rDeltas[i];
                }
            }

            for (int i = 0; i < columns.Length; i++)
            {
                if (i > 0)
                    columns[i - 1].Height += lDeltas[i];
                if (i < columns.Length - 1)
                    columns[i + 1].Height += rDeltas[i];
            }
        }

        foreach (var particle in particles)
            UpdateParticle(particle);

        particles = particles.Where(x => x.Position.X >= 0 && x.Position.X <= 800 && x.Position.Y - 5 <= GetHeight(x.Position.X)).ToList();
    }

    public void DrawToRenderTargets()
    {
        GraphicsDevice device = spriteBatch.GraphicsDevice;
        device.SetRenderTarget(metaballTarget);
        device.Clear(Color.Transparent);

        // draw particles to the metaball render target
        spriteBatch.Begin(0, BlendState.Additive);
        foreach (var particle in particles)
        {
            Vector2 origin = new Vector2(particleTexture.Width, particleTexture.Height) / 2f;
            spriteBatch.Draw(particleTexture, particle.Position, null, Color.White, particle.Orientation, origin, 2f, 0, 0);
        }
        spriteBatch.End();

        // draw a gradient above the water so the metaballs will fuse with the water's surface.
        pb.Begin(PrimitiveType.TriangleList);

        const float thickness = 20;
        float scale = Scale;
        for (int i = 1; i < columns.Length; i++)
        {
            Vector2 p1 = new Vector2((i - 1) * scale, columns[i - 1].Height);
            Vector2 p2 = new Vector2(i * scale, columns[i].Height);
            Vector2 p3 = new Vector2(p1.X, p1.Y - thickness);
            Vector2 p4 = new Vector2(p2.X, p2.Y - thickness);

            pb.AddVertex(p2, Color.White);
            pb.AddVertex(p1, Color.White);
            pb.AddVertex(p3, Color.Transparent);

            pb.AddVertex(p3, Color.Transparent);
            pb.AddVertex(p4, Color.Transparent);
            pb.AddVertex(p2, Color.White);
        }

        pb.End();

        // save the results in another render target (in particlesTarget)
        device.SetRenderTarget(particlesTarget);
        device.Clear(Color.Transparent);
        spriteBatch.Begin(0, null, null, null, null, alphaTest);
        spriteBatch.Draw(metaballTarget, Vector2.Zero, Color.White);
        spriteBatch.End();

        // switch back to drawing to the backbuffer.
        device.SetRenderTarget(null);
    }

    public void Draw()
    {
        Color lightBlue = new Color(0.2f, 0.5f, 1f);

        // draw the particles 3 times to create a bevelling effect
        spriteBatch.Begin();
        spriteBatch.Draw(particlesTarget, -Vector2.One, new Color(0.8f, 0.8f, 1f));
        spriteBatch.Draw(particlesTarget, Vector2.One, new Color(0f, 0f, 0.2f));
        spriteBatch.Draw(particlesTarget, Vector2.Zero, lightBlue);
        spriteBatch.End();

        // draw the waves
        pb.Begin(PrimitiveType.TriangleList);
        Color midnightBlue = new Color(0, 15, 40) * 0.9f;
        lightBlue *= 0.8f;

        float bottom = spriteBatch.GraphicsDevice.Viewport.Height;
        float scale = Scale;
        for (int i = 1; i < columns.Length; i++)
        {
            Vector2 p1 = new Vector2((i - 1) * scale, columns[i - 1].Height);
            Vector2 p2 = new Vector2(i * scale, columns[i].Height);
            Vector2 p3 = new Vector2(p2.X, bottom);
            Vector2 p4 = new Vector2(p1.X, bottom);

            pb.AddVertex(p1, lightBlue);
            pb.AddVertex(p2, lightBlue);
            pb.AddVertex(p3, midnightBlue);

            pb.AddVertex(p1, lightBlue);
            pb.AddVertex(p3, midnightBlue);
            pb.AddVertex(p4, midnightBlue);
        }

        pb.End();
    }
}

Then in the Game1.cs I have the following LoadContent method

protected override void LoadContent()
    {
        // Create a new SpriteBatch, which can be used to draw textures.
        spriteBatch = new SpriteBatch(GraphicsDevice);
        font = Content.Load<SpriteFont>("Font");
        particleImage = Content.Load<Texture2D>("metaparticle");
        backgroundImage = Content.Load<Texture2D>("sky");
        rockImage = Content.Load<Texture2D>("rock");
        water = new Water(GraphicsDevice, particleImage);
        .
        .
        .
    }

In my update method I have the following (along with other code for the game, i am just showing water part)

protected override void Update(GameTime gameTime)
    {
        lastKeyState = keyState;
        keyState = Keyboard.GetState();
        lastMouseState = mouseState;
        mouseState = Mouse.GetState();

        water.Update();

        Vector2 mousePos = new Vector2(mouseState.X, mouseState.Y);
        // if the user clicked down, create a rock.
        if (lastMouseState.LeftButton == ButtonState.Released && mouseState.LeftButton == ButtonState.Pressed)
        {
            rock = new Rock
            {
                Position = mousePos,
                Velocity = (mousePos - new Vector2(lastMouseState.X, lastMouseState.Y)) / 5f
            };
        }

        // update the rock if it exists
        if (rock != null)
        {
            if (rock.Position.Y < 240 && rock.Position.Y + rock.Velocity.Y >= 240)
                water.Splash(rock.Position.X, rock.Velocity.Y * rock.Velocity.Y * 5);

            rock.Update(water);

            if (rock.Position.Y > GraphicsDevice.Viewport.Height + rockImage.Height)
                rock = null;
        }

Then in the Draw method I have the following (when the active enum is InGame)

case ActiveScreen.InGame:

                water.DrawToRenderTargets();
                level.Draw(gameTime, spriteBatch);
                DrawHud();
                spriteBatch.Begin();
                spriteBatch.Draw(backgroundImage, Vector2.Zero, Color.White);

                if (rock != null)
                    rock.Draw(spriteBatch, rockImage);
                spriteBatch.End();
                water.Draw();

                break;

My problem is this obviously takes up the entire screen. I realise why it takes up the entire screen but I can't figure out how to scale it down and set it on a fixed location in the game. If anyone could read through this and direct me towards how I would go about scaling this down successfully, I'd greatly appreciate it.

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closed as off-topic by Byte56 Jun 29 '13 at 19:34

  • This question does not appear to be about game development within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

4  
I wrote up a pretty detailed answer on a similar question before. The sample code might help you. Which part of your code is the problem? How have you tried fixing it? –  Anko Mar 24 '13 at 17:36
    
I'm not sure...in the Water.cs I am trying to alter the scale as currently its being draw to cover the screen width. Everytime I try to alter this, I get out of bounds exceptions. –  UserBruiser Mar 24 '13 at 17:43
    
This question appears to be off-topic because it is far too localized. Essentially you're asking for someone to rewrite this tutorial code for you so it works in your game. –  Byte56 Jun 29 '13 at 19:34
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1 Answer 1

Well, there are two ways of doing this:

  1. Draw the entire Water object to a render target, then draw the final water target scaled and on the position you want. (this is the simplest way).
  2. Draw the Water in a constrained area. For this you'll need do to something like this:
    • Create the Water by specifying a Rectangle as target in the constructor.
    • Every reference to GraphicsDevice.Viewport should be replaced with the target rectangle
    • I assume that you will give the 'right' - real - position as the Splash method parameter (xPosition) so everything else will be fine when drawn.

PS: You said something about OutOfBoundsException. Please gives us more details if that's the case anymore.

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