I'm making a space invaders clone and before I get into any of the hard coding I want to figure something out. For my aliens I'm going to be using a sprite sheet that has only two images of the alien. One with its arms up and one with them down. I know how to animate the image from the sprite sheet but the issue is getting many of these aliens onto the screen. I was thinking about creating an array with all of them in the array but would that make sense to do it that way? or is there a more simple way to this?
C# array question
Personally I would use a List. It would be a lot easier to add and remove the aliens. Plus you won't be limited in the size like an array.
Author
That could work too. But now I had another thought: would it be even easier to make a whole separate class for the alien? And then just put whatever number of aliens I want on the screen in that list? I think I'm confusing myself tho...
Take a look at Microsoft's XNA tutorial example. I think it might help guide you to what you are looking for.
http://xbox.create.msdn.com/en-US/education/tutorial/2dgame/creating_enemies
Personally I would use a List. It would be a lot easier to add and remove the aliens. Plus you won't be limited in the size like an array.
A c# list<> is a dynamically sized array class, much like c++'s vector. This is probably what you want.
However if you know a maximum number of aliens then an array would be fine, you would need a flag to know which ones are active, so you can selectively draw and update only the ones you want.
Author
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
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;
namespace WindowsGame3
{
public class Alien
{
public Texture2D Texture { get; set; }
public int Rows { get; set; }
public int Columns { get; set; }
private int currentFrame;
private int totalFrames;
public Alien(Texture2D texture, int rows, int columns)
{
Texture = texture;
Rows = rows;
Columns = columns;
currentFrame = 0;
totalFrames = Rows * Columns;
}
public void Update()
{
currentFrame++;
if (currentFrame == totalFrames)
currentFrame = 0;
}
public void Draw(SpriteBatch spriteBatch, Vector2 location)
{
int width = Texture.Width / Columns;
int height = Texture.Height / Rows;
int row = (int)((float)currentFrame / (float)Columns);
int column = currentFrame % Columns;
Rectangle sourceRectangle = new Rectangle(width * column, height * row, width, height);
Rectangle destinationRectangle = new Rectangle((int)location.X, (int)location.Y, width, height);
spriteBatch.Begin();
spriteBatch.Draw(Texture, destinationRectangle, sourceRectangle, Color.White);
spriteBatch.End();
}
}
}
Thats my alien class so far. The only issue I'm having is that its switching between the two frames way too fast. How would I slow this down?
Author
Also I think I'm going to use an array instead of a list. I figured there to be 24 aliens on the screen and I think that an array would be easier to work with since I'm only destroying the aliens, not adding any
Alien[] alienGroup = new Alien[24];
for (int x = 0; x < alienGroup.Length; x++)
{
alienGroup[x] = new Alien(alienSprite, 1, 2);
}
this will work i hope? unless it would be better to make a two dimensional ray. Im thinking 4 rows of 6 aliens, but im not sure which would be easier to draw
An array is probably more complex than a list. This is because with an array you have to manually track two things, the array itself and a counter of the number of active objects. You also may need to implement logic to "shuffle" the aliens in the array when one in the middle dies. A list handles this all for you.
Alternatively, you could use "null" to represent dead aliens. However, now your code must carefully check for null before accessing any element of the array.
A two dimensional array might make sense if you were writing a game like Space Invaders, where the aliens have some kind of pattern or formation. In particular, it allows you to avoid storing the positions of individual aliens, their position on the screen or for collision can be inferred from the indices of their entry in the matrix. If your game just spawns aliens in random locations, then I would not recommend a multi-dimensional array. However, if your game has some kind of limited, grid based levels, then storing all the objects (including the player, any obstacles, pickups etc) in a multi-dimensional array would make sense, though you may wish to store the aliens in a separate container anyway.
As for the problem of your sprites animating too fast, you need to incorporate real world time into your update cycle. Otherwise your animations will play at different speeds on different machines, and they will slow down if the game starts to get "busy" - such as levels with more enemies, or if the enemies shoot lots of bullets or there are explosions, etc.
Alternatively, you could use "null" to represent dead aliens. However, now your code must carefully check for null before accessing any element of the array.
A two dimensional array might make sense if you were writing a game like Space Invaders, where the aliens have some kind of pattern or formation. In particular, it allows you to avoid storing the positions of individual aliens, their position on the screen or for collision can be inferred from the indices of their entry in the matrix. If your game just spawns aliens in random locations, then I would not recommend a multi-dimensional array. However, if your game has some kind of limited, grid based levels, then storing all the objects (including the player, any obstacles, pickups etc) in a multi-dimensional array would make sense, though you may wish to store the aliens in a separate container anyway.
As for the problem of your sprites animating too fast, you need to incorporate real world time into your update cycle. Otherwise your animations will play at different speeds on different machines, and they will slow down if the game starts to get "busy" - such as levels with more enemies, or if the enemies shoot lots of bullets or there are explosions, etc.
Author
With the way the aliens are layed out, an array would make more sense i think. There a 4 rows of six, and when one dies the dont squish together. They stay in the same pattern but with just one missing from the area that was hit
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