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How to create a game

I will begin with a simplified explanation of how to create games using XNA.

Game1 extends Game

To begin with, note that the Game1 class extends the Game class. We do not modify the Game class. Instead, we modify the behavior of the Game class by extending it and overriding some of its methods.

Main method calls the Run method

As you saw earlier in Listing 2 , the Main method in the file named Program.cs instantiates an object of the Game1 class (shown in Listing 3 ) and calls the Run method on that object. That starts the program running.

The Run method

The class named Game1 does not define and does not override a method named Run . However, it does inherit a method named Run from the Game class.

Therefore, when the Run method is called on the object of the Game1 class, the version of the Run method that is defined in the superclass named Game is executed.

Override five methods

The skeleton code for the Game1 class in Listing 3 overrides the following five methods inherited from the Game class:

  1. Initialize
  2. LoadContent
  3. UnloadContent
  4. Update
  5. Draw

Initialization

The first three methods contain code that is needed to get everything initialized at the start of the game play and to shut down the program at theend of the game play.

The game loop

Once the game is initialized, the Run method, or some method called by the Run method ping-pongs back and forth between calls to the overridden Update method and the overridden Draw method. (Note, however that the two methods don't necessarily take turns executing.)

Override Update for game logic

You override the Update method to create the program logic associated with game play. To accomplish this, you will likely need to defineother methods, define other classes, instantiate objects of other classes, call methods on those objects, testthe keyboard, test the mouse, etc. In other words, at this point you need to know how to program in C# .

Override the Draw method

You override the Draw method to cause the various graphics objects in your game to be rendered in the game window shown in Figure 1 .

This module includes an explanation of a very simple program that displays a green arrow sprite near the upper-left corner of the game window (see Figure 3 ).

Preview

I will create a simple Windows game application that imports the image shown in Figure 2 . Note that this is a rectangular image with an (almost) transparent background. (The values of the alpha bytes outside the blueelliptical shape are about 5.)

Figure 2 . Raw image with an (almost) transparent background.

Missing image

If you would like to replicate my program using this image, you should be able to right-click on the image in Figure 2 , download it, and save it on your computer. You can save it under any name you choose but the file name extensionshould be png .

Program output

The program displays the image near the upper-left corner of the game window and honors the transparency of the background as shown in Figure 3 .

Figure 3 . Cropped upper-left corner of the game window.

Missing image

What if you don't honor the transparent background?

Figure 4 shows the result of causing the alpha transparency value to be ignored and allowing the pixels that are almosttransparent in Figure 3 to be opaque.

Questions & Answers

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
im not good at math so would this help me
Rachael Reply
yes
Asali
I'm not good at math so would you help me
Samantha
what is the problem that i will help you to self with?
Asali
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
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
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
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
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
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.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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