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General background information

You learned how to design, create, and use a simple Sprite class in an earlier module. You also learned to use a generic List object to store references to objects of the Sprite class.


I will explain improvements made to the Sprite class and will show you how to write a Game1 class that takes advantage of those improvements.

The screen output

Figure 1 shows a reduced screen shot of the program while it is running.

Figure 1 . Screen shot of the running program.

missing image

Lots and lots of sprites

When this screen shot was taken, the program had 24 space rocks, 12 red power pills and six UFOs all navigating in the game window.

Discussion and sample code

As usual, I will discuss and explain the program code in fragments. A complete listing of the Sprite class is provided in Listing 19 and a complete listing of the Game1 class is provided in Listing 20 .

The Sprite class

The Sprite class begins in Listing 1 with the declaration of several instance variables.

Listing 1 . Beginning of the Sprite class.

namespace XNA0128Proj { class Sprite {private Texture2D image; private Vector2 position = new Vector2(0,0);private Vector2 direction = new Vector2(0,0); private Point windowSize;private Random random; double elapsedTime;//in milliseconds//The following value is the inverse of speed in // moves/msec expressed in msec/move.double elapsedTimeTarget;

The purpose of these instance variables will become clear later in the discussion.


This class has the following properties:

  • Position - position of the sprite in the game window relative to the upper left corner of the game window. The X and Y values aresaved as type Vector2 in the instance variable named position .
  • WindowSize - The dimensions of the game window. The width and height values are saved as type Point in the instance variable named windowSize .
  • Direction - Direction of motion of the sprite expressed as a 2D vector with an X and a Y component. The length of this vector is thedistance that the sprite moves each time it moves. The values are saved as type Vector2 in the instance variable named direction .
  • Speed - Speed of the sprite expressed in moves per millisecond. The actual speed in pixels per millisecond is the product ofthis value and the length of the direction vector.

Other instance variables

In addition, the class has the following instance variables that are set either by the constructor or by a method:

  • image - the image that is drawn to represent the sprite in the game window. The image can be modified as the game progresses throughcalls to the SetImage method.
  • random - a reference to a random number generator.
  • elapsedTime - used to keep track of the amount of elapsed time in milliseconds since the last time that the sprite wasactually moved.
  • elapsedTimeTarget - will be explained later.

The first three property accessor methods

The first three property accessor methods are shown in Listing 2 .

Listing 2 . The first three property accessor methods.

//Position property accessor public Vector2 Position {get { return position;} set {position = value; }//end set}//end Position property accessor //-------------------------------------------------////WindowSize property accessor public Point WindowSize {set { windowSize = value;}//end set }//end WindowSize property accessor//-------------------------------------------------// //Direction property accessorpublic Vector2 Direction { get {return direction; }set { direction = value;}//end set }//end Direction property accessor

Questions & Answers

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s. Reply
how to fabricate graphene ink ?
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What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
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Sanket Reply
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Damian Reply
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Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
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In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
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silver nanoparticles could handle the job?
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I'm interested in Nanotube
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can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
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Source:  OpenStax, Xna game studio. OpenStax CNX. Feb 28, 2014 Download for free at https://legacy.cnx.org/content/col11634/1.6
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