source: 2016/23/ohjaajat/Punasininen/Punasininen/Punasininen/Shader.cs @ 7209

using Jypeli;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class Shader
{
    private Effect effect;
    private RenderTarget2D renderTarget;
    private SpriteBatch spriteBatch;
    private GraphicsDevice device;
    private Camera camera;

    struct Shockwave
    {
        public Vector Center;
        public double Time;
    }

    private const int MAX_WAVES = 3;
    private readonly Shockwave[] waves = new Shockwave[MAX_WAVES];
    private int waveIndex = 0;

    public Shader(GraphicsDevice device, ContentManager content, Camera camera)
    {
        for (int i = 0; i < MAX_WAVES; i++)
        {
            waves[i].Time = 1000f;
        }

        renderTarget = new RenderTarget2D(device,
            device.PresentationParameters.BackBufferWidth,
            device.PresentationParameters.BackBufferHeight);

        effect = content.Load<Effect>("Shockwave");
        spriteBatch = new SpriteBatch(device);
        this.camera = camera;
        this.device = device;
    }

    public void NewWave(Vector position)
    {
        waves[waveIndex].Time = 0f;
        waves[waveIndex].Center = position;
        waveIndex = ++waveIndex % MAX_WAVES;
    }

    public void Draw(GameTime gameTime, Action<GameTime> baseDraw)
    {

        device.Clear(Microsoft.Xna.Framework.Color.Black);
        device.SetRenderTarget(renderTarget);

        baseDraw(gameTime);

        device.SetRenderTarget(null);

        var projection = Matrix.CreateOrthographicOffCenter(0,
          device.Viewport.Width, device.Viewport.Height, 0, 0, 1);
        var halfPixelOffset = Matrix.CreateTranslation(-0.5f, -0.5f, 0);
        effect.Parameters["MatrixTransform"].SetValue(halfPixelOffset * projection);

        Vector resolution = new Vector(device.Viewport.Width, device.Viewport.Height);
        Vector2 resolution2 = new Vector2(device.Viewport.Width, device.Viewport.Height);
        effect.Parameters["Resolution"].SetValue(resolution2);

        // TestShader
        //effect.Parameters["Resolution"].SetValue(new Vector2(GraphicsDevice.PresentationParameters.BackBufferWidth, GraphicsDevice.PresentationParameters.BackBufferHeight));
        //effect.Parameters["Misalign"].SetValue(0.003f);
        //effect.Parameters["Time"].SetValue(100f * (float)gameTime.TotalGameTime.TotalSeconds);

        // Shockwave
        var waveArray = new Vector4[MAX_WAVES];
        for (int i = 0; i < MAX_WAVES; i++)
        {
            waves[i].Time += 0.5 * gameTime.ElapsedGameTime.TotalSeconds;
            Vector screenCoord = camera.WorldToScreen(waves[i].Center);
            screenCoord.Y = resolution.Y - screenCoord.Y;
            screenCoord.X /= resolution.X;
            screenCoord.Y /= resolution.Y;
            screenCoord += new Vector(0.5f, -0.5f);

            var v = new Vector4((float)screenCoord.X, (float)screenCoord.Y, (float)waves[i].Time, 1f);
            waveArray[i] = v;
        }
        effect.Parameters["Waves"].SetValue(waveArray);

        device.Clear(Microsoft.Xna.Framework.Color.Black);
        spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend);
        effect.CurrentTechnique.Passes[0].Apply();
        spriteBatch.Draw(renderTarget, Vector2.Zero, Microsoft.Xna.Framework.Color.White);
        spriteBatch.End();
    }
}