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This is another manifestation of an object knowing how to behave with minimal supervision. The overriddenGame.Draw method doesn't know and doesn't care where the Sprite object should be positioned or what image it should draw to represent itself. TheGame.Draw method simply knows that every Sprite object must redraw itself at the appropriate position with the appropriate image at this point in time.Decisions regarding position and image are left up to the Sprite object.

Regardless of whether or not a sprite has decided to move, it should cause itself to be redrawn in the game window because its image has just been replacedby a bunch of CornflowerBlue pixels.

Not the same approach as some other game engines

Some game engines take a different approach and in the interest of speed, redraw only those portions of the game window that have changed. This can leadto a great deal of complexity and it is often the responsibility of the game programmer to manage that complexity.

That is not the case with XNA. From the viewpoint of the XNA game programmer, the entire game window is redrawn once during every iteration of the game loop.This causes XNA to be easier to program than some other game engines. On the other hand, it might be argued that XNA sacrifices speed for simplicity.

The end of the program

Listing 18 also signals the end of the overridden Game.Draw method, the end of the Game1 class, and the end of the program.

Run the program

I encourage you to copy the code from Listing 19 and Listing 20 . Use that code to create an XNA project. (You should be able to use any small image filesas sprites.) Compile and run the project. Experiment with the code, making changes, and observing the results of your changes. Make certain that you canexplain why your changes behave as they do.

Run my program

Click here to download a zip file containing my version of the program. Extract the folder named XNA0128Proj from the zip file and save it somewhere on your disk. Start Visual C# 2010 Express and select Open Project... from the File menu. Navigate to the project folder and select the file with the extension of .sln . This should cause the project to open and be ready to run or debug as described in the earlier module titled Getting Started .


In this module, you learned how to add more sophistication to the Sprite class that was introduced in an earlier module.

What's next?

We're getting very close to being able to write a 2D arcade style game involving UFOs, space rocks, and power pills. There are just a few more toolsthat we need and I will show you how to create those tools in the upcoming modules.

The critical tools are:

  • The ability to detect collisions between sprites.
  • The ability to control the movement of one or more sprites using the keyboard or the mouse.

Once we have those tools, we can write a game where the challenge is to cause the UFO to successfully navigate across the game window without colliding with aspace rock, so I will concentrate on those two tools in the next few modules. (There are probably other games that we could also create using those tools.)

Questions & Answers

what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
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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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