source: 2010/23/sijoseha/alpha/Effects/ParticleSystem.cs @ 822

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;
using Microsoft.Xna.Framework.Net;
using Microsoft.Xna.Framework.Storage;

namespace Effects
{
    public abstract class ParticleSystem : DrawableGameComponent
    {
        private ParticleGame game;

        private Particle[] particles;

        /// <summary>
        /// There are variables that need to be set by subclasses
        /// </summary>
        #region Subclass variables
        protected Vector2 position;

        protected String textureName;

        protected String innerTextureName;
        protected String outerTextureName;

        protected float minScale;
        protected float maxScale;

        protected float rotation;

        protected Vector2 origin;

        protected Vector2 minVelocity;
        protected Vector2 maxVelocity;

        protected float minLifetime;
        protected float maxLifetime;

        #endregion

        private enum TextureType
        {
            Single,
            Dual
        };

        private TextureType textureType;

        private Texture2D texture, innerTexture, outerTexture;
        private Vector2 textureOrigin;

        private int maxAmountOfParticles;
        public int MaxAmountOfParticles
        {
            get { return maxAmountOfParticles; }
            set { maxAmountOfParticles = value; }
        }

        public ParticleSystem(ParticleGame game, Vector2 position, String textureName)
            : base(game)
        {
            textureType = TextureType.Single;
            this.game = game;
        }

        public ParticleSystem(ParticleGame game, Vector2 position, String innerTextureName, String outerTextureName)
            : base(game)
        {
            textureType = TextureType.Dual;
            this.game = game;
        }

        protected abstract void InitializeParticles();

        public override void Initialize()
        {
            for (int i = 0; i < maxAmountOfParticles; i++)
            {
                particles[i] = new Particle();
            }
            base.Initialize();
        }

        protected override void LoadContent()
        {
            particles = new Particle[maxAmountOfParticles];
            if (textureType == TextureType.Single)
            {
                texture = game.Content.Load<Texture2D>(textureName.ToString());
                textureOrigin.X = texture.Width / 2;
                textureOrigin.Y = texture.Height / 2;
            }
            if (textureType == TextureType.Dual)
            {
                innerTexture = game.Content.Load<Texture2D>(innerTextureName.ToString());
                outerTexture = game.Content.Load<Texture2D>(outerTextureName.ToString());
                textureOrigin.X = outerTexture.Width / 2;
                textureOrigin.Y = outerTexture.Height / 2;
            }

            base.LoadContent();
        }

        public override void Update(GameTime gameTime)
        {

            base.Update(gameTime);
        }

        public override void Draw(GameTime gameTime)
        {
            game.SpriteBatch.Begin();
            foreach (Particle p in particles)
            {
                if (!p.Alive)
                {
                    continue;
                }
                if (textureType == TextureType.Single)
                {
                    game.SpriteBatch.Draw(texture, p.Position, null, Color.White, p.Rotation, textureOrigin, p.Scale, SpriteEffects.None, 1.0f);
                }
                if (textureType == TextureType.Dual)
                {
                    game.SpriteBatch.Draw(outerTexture, p.Position, null, Color.White, p.Rotation, textureOrigin, p.Scale, SpriteEffects.None, 1.0f);
                    game.SpriteBatch.Draw(innerTexture, p.Position, null, Color.White, p.Rotation, textureOrigin, p.Scale, SpriteEffects.None, 1.0f);
                }
            }
            base.Draw(gameTime);
        }
    }
}