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Relatively smooth motion

When I compile and run this program, I see the sprite moving with a relatively smooth motion. Unless your computer is very slow, you should probablysee the same thing.

Beginning of the class named Slick0150a

Listing 1 shows the beginning of the class definition for the class named Slick0150a .

Listing 1 . Beginning of the class named Slick0150a.
public class Slick0150a extends BasicGame{Image bug = null; Image background = null;float backgroundWidth;float backgroundHeight;float bugX = 100; float bugY = 100;float bugWidth; float bugHeight;float bugXDirection = 1.0f;//initial direction to rightfloat bugYDirection = 1.0f;//initial direction is downfloat xStep = 4.0f;//horizontal step size float yStep = 3.0f;//vertical step sizefloat bugScale = 0.75f;//drawing scale factor//Used to compute and display the time required for the// bug to make each round trip across the game window // and back.long oldTime = 0; long traversalTime = 0;//Frame rate we would like to see and maximum frame// rate we will allow. int targetFPS = 60;

Listing 1 consists entirely of instance variable declarations. The purpose of each of these variables shouldbecome clear as they are used later in the code. No explanation beyond the embedded commentsshould be needed at this point.

The constructor and the main method

There is nothing new in the constructor and the main method. You can view them both in Listing 9 .

The init method

The init method is shown in Listing 2 . I will explain the new material in this method.

Listing 2 . The init method for Slick0150a.
public void init(GameContainer gc) throws SlickException {oldTime = gc.getTime(); bug = new Image("ladybug.png");background = new Image("background.jpg");backgroundWidth = background.getWidth(); backgroundHeight = background.getHeight();bugWidth = bug.getWidth()*bugScale;bugHeight = bug.getHeight()*bugScale;System.out.println( "backgroundWidth: " + backgroundWidth);System.out.println( "backgroundHeight: " + backgroundHeight);System.out.println("bugWidth: " + bugWidth); System.out.println("bugHeight: " + bugHeight);gc.setTargetFrameRate(targetFPS);//set frame rate}//end init

Get the time

The GameContainer class provides a method named getTime , which is described simply as:

"Get the accurate system time."

I am interpreting this to mean that the method will return the system time good to one millisecond relative to a well-defined time origin.

(Standard Java uses January 1, 1970 as the origin or epoch of time but Slick2D may use a different origin. Since we will be working with changes intime and not absolute time, the time origin doesn't matter.)

The init method in Listing 2 calls the getTime method to get and save the time in an instance variable named oldTime . The values in this variable will be used later to compute the round-trip timerequired for the sprite to move across the game window and back to the starting point at the right edge of the window.

Questions & Answers

what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
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
How can I make nanorobot?
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
how can I make nanorobot?
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.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Mueller Reply
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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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