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Learn how a game program written with the Slick game library creates and maintains a game loop.

Table of contents


This module is one in a collection of modules designed to teach you about the anatomy of a game engine.

Although the modules in this collection will concentrate on the Java game library named Slick2D, theconcepts involved and the knowledge that you will gain is applicable to different game engines written in different programming languages as well.

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the Figuresand Listings while you are reading about them.


  • Figure 1 . Screen output from program named Slick0130a.


  • Listing 1 . The start method of the AppGameContainer class.
  • Listing 2 . The gameLoop method of the AppGameContainer class.
  • Listing 3 . Beginning of the updateAndRender method of the GameContainer class.
  • Listing 4 . The remainder of the updateAndRender method of the GameContainer class.
  • Listing 5 . Beginning of the class named Slick0130a.
  • Listing 6 . The main method.
  • Listing 7 . The overridden init method.
  • Listing 8 . The overridden update method.
  • Listing 9 . The overridden render method.
  • Listing 10 . Source code for the program named Slick0130a.


What you have learned

The main purpose of this and the previous module is to analyze the behavior of the Slick2D game engine when you call the start method to cause a Slick2D game program to start running.

In the previous module, you learned how and why you should extend the BasicGame class instead of implementing the Game interface directly.

You learned about the behavior of the constructors for the AppGameContainer class.

You learned that the start method of the AppGameContainer class (see Listing 1 ) calls the following three methods:

  • setup
  • getDelta
  • gameLoop

You learned about the behavior of the setup and getDelta methods.

What you will learn

I will explain the overall behavior of the gameLoop method in this module.

In addition, you will learn

  • about a property of the GameContainer class named running , and how it is used by the start method to keep the game loop running,
  • about the salient features of the gameLoop method of the AppGameContainer class,
  • about the updateAndRender method of the GameContainer class and how it decides when and if to call the update and render methods of the object of the Game class that is wrapped in the container,
  • about the difference between normal delta and smoothed delta,
  • about minimumLogicInterval and maximumLogicInterval and how the contents of those two variables are used to determine if, when, and how many times to call the update method during each iteration of the game loop,
  • how the contents of minimumLogicInterval and maximumLogicInterval are used to determine the value that is passed as delta each time the update method is called,
  • that the render method is normally called once and only once during each iteration of the game loop,
  • how you can use the value of delta that is received by the update method to control the behavior of a game program,
  • that you can set the size of the game window when you instantiate an object of the AppGameContainer class by passing dimension parameters to the constructor,
  • that you can set the target frame rate by calling the setTargetFrameRate method on the GameContainer object, and
  • how to display text in the game window.

Questions & Answers

find the 15th term of the geometric sequince whose first is 18 and last term of 387
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virgelyn Reply
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kinnecy Reply
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I'm not sure why it wrote it the other way
I got X =-6
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oops. ignore that.
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Commplementary angles
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a perfect square v²+2v+_
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Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
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rolling four fair dice and getting an even number an all four dice
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Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
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No. 7x -4y is simplified from 4x + (3y + 3x) -7y
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. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
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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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how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
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.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
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Source:  OpenStax, Anatomy of a game engine. OpenStax CNX. Feb 07, 2013 Download for free at https://legacy.cnx.org/content/col11489/1.13
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