TweetFollow Us on Twitter

REALbasic Sprites Volume Number: 16 (2000)
Issue Number: 8
Column Tag: Programming

REALbasic Sprites

By Erick J. Tejkowski

Develop powerful games in minutes

Introduction

Game programming has long been a tradition of highly specialized source code, libraries, and programming trickery, strictly for übergeeks. Until now. Armed with a copy of REALbasic and this article, you will be writing your own games in no time at all.

For high-speed games, it is customary for programmers to use special code to draw at high speeds (often referred to as "blitting" routines). This stems from the fact that the native drawing routines available in the Mac Toolbox are too slow for fast drawing, such as that required by animation. Beginners will be glad to learn that REALbasic has these abilities built in. With only a few lines of code, a programmer can attain high-speed sprite-based animation. Add a few more lines of code and you have a game. REALbasic takes care of all the nasty drawing routines behind the scenes and lets us focus on the elements of the game. This article will demonstrate animation and game creation using REALbasic sprites. By the end of the article, you should be able to complete a small arcade-style game.

Building the Sprites

Begin the game project by opening your favorite resource editor. For our purposes, the free ResEdit from Apple will do just fine. Create a new file and name it "Resources". This is the only name REALbasic understands for resource files added directly to projects in the IDE, so be sure to spell it correctly. In this new resource file, create three resources of type 'cicn' and change the ID# to 1280, 1290, and 1300 respectively by selecting the Resource:Get Resource Info menu. In cicn #1280, create a graphic for the hero of our game. In cicn #1290, draw an adversary. Finally, cicn #1300 contains a picture of a projectile. For this example, we will use an airplane theme. By now, you should have something that looks like Figure 1.


Figure 1. The Sprite Graphics.

Now that the sprite graphics have been created, save the Resources file and start REALbasic.

Building the Project

When REALbasic starts, a new project is created automatically. Drag the newly created resource file into the project. Now, open Window1 and drag a StaticText , a PushButton , and a SpriteSurface control onto the window. The StaticText will display the results of the game (i.e. win or lose), the PushButton will start the game, and the SpriteSurface will control all of the animation and game play. Figure 2 shows the completed interface.


Figure 2. The Completed Window1 Interface.

Once the interface has been built, double click Window1 to open the Code Editor. With the Code Editor opened, create the Properties in Listing 1 by selecting New Property from the Edit menu.

Listing 1. Window1 Properties.

BadguySprite(10) as Sprite
GoodGuySprite as Sprite
GunSprite as Sprite	
gunvisible as Boolean
NumOfBadGuys as Integer
leftEdge as Integer
topEdge as Integer

Sprite properties are pictures that can be controlled by a SpriteSurface. We will need 10 sprites representing the attacking enemies, one representing the hero, and one used for the gunfire that the hero can shoot. The Boolean variable gunvisible will allow us to turn the gunfire on and off. The integer NumOfBadGuys , as one might expect, will keep track of the number of BadguySprites remaining. The final two integer variables (leftEdge and topEdge) will be used to center the SpriteSurface on the screen.

In addition to these properties, create three methods named InitSprites, ClearAllSprites, and RemakeGun by selecting New Method from the Edit menu. The InitSprites method will initialize all of the sprites defined in Listing 1. Open the Code Editor to the InitSprites method and enter the code from Listing 2.

Listing 2. The InitSprites Method.

Sub InitSprites()
dim p as picture
dim i as integer

//init the good guy
p=app.resourceFork.getcicn(1280)
GoodGuySprite=SpriteSurface1.NewSprite(p,32,32)
GoodGuySprite.x=300
GoodGuySprite.y=435
GoodGuySprite.group=1

//init the gunfire
p=app.resourceFork.getcicn(1300)
GunSprite=SpriteSurface1.NewSprite(p,32,32)
GunSprite.x=-200
GunSprite.y=467
GunSprite.group=2
gunvisible=false

//init the bad guys
p=app.resourceFork.getcicn(1290)
for i=1 to 10
BadguySprite(i)=SpriteSurface1.NewSprite(p,32,32)
BadguySprite(i).x=rnd*600
BadguySprite(i).y=rnd*200-250
BadguySprite(i).group=3
next

NumOfBadGuys=10
End Sub

The InitSprites method demonstrates how each of the Sprites is created. First, the icons created earlier are opened into a Picture object. Next, the NewSprite method of SpriteSurface1 is called, passing the Picture, and Width and Height of the Picture as parameters. Once the Sprite has been created, its X and Y positions are initialized. The SpriteSurface will measure 640x480, so the GoodGuySprite will begin life somewhere near the bottom middle of the screen. The gunfire starts off as not being visible (i.e. gunvisible=false), so we assign its X postion somewhere off the screen (GunSprite.x=-200). Later, when we want it visible to the user, we will simply move it to a positive X position. The ten BadguySprites will begin at random X positions and Y positions somewhere between -250 and -50, making them initially invisible. This will change later, however, when they move down the screen towards the GoodyguySprite. The last thing to notice here is the Group property of each of the Sprites. The Group number is used for detecting collisions. Sprites with the same Group number will not collide with each other. Sprites with different Group numbers produce collisions. Now, when we talk about producing collisions, what this really means is that the Collision Event of the SpriteSurface will be fired. For now, it is sufficient to know that the GunSprite and the BadGuys have different Group numbers so that they may collide. Further, the BadGuySprites have a Group number that is different from the GoodguySprite, allowing them to collide.

Since all good things must come to an end, we need to include some code to destroy everything we have created. Open the Code Editor, navigate to the ClearAllSprites method, and enter the code in Listing 3. During the execution of the game, we may need to kill a sprite (e.g. when GunSprite and badguySprite collide). Therefore, we should not assume that all sprites will always be around. This is the reason we check for nil status of a sprite before trying to kill it. If we try to kill a non-existent sprite, an error will result causing the application to crash.

Listing 3. The ClearAllSprites Method.

Sub ClearAllSprites()
dim i as integer
//kill the GoodguySprite
if GoodGuySprite<>nil then
GoodGuySprite.close
end if
//kill the GunSprite
if GunSprite<>nil then
GunSprite.close
end if
//kill the BadguySprites
for i=1 to 10
if BadguySprite(i)<>nil then
BadguySprite(i).close
end if
next
End Sub

One final auxiliary method to code is called RemakeGun. This method will allow us to recreate a GunSprite in the middle of game play. Although we already created one in the InitSprites method, it might be destroyed during game play when it collides with a BadguySprite. Open the Code Editor window, navigate to the RemakeGun method, and enter the code in Listing 4.

Listing 4. The RemakeGun Method.

Sub RemakeGun()
dim p as picture
//reinitialize the gunfire
p=app.resourceFork.getcicn(1300)
GunSprite=SpriteSurface1.NewSprite(p,32,32)
GunSprite.x=-200
GunSprite.y=467
GunSprite.group=2
gunvisible=false
End Sub

With the window's properties and methods defined, it is time to add functionality to the various controls. To begin, fill the screen with Window1 by adding code into its Open event. This is really only cosmetic in nature. The SpriteSurface will later take over the whole screen anyway. This is what the player will see before the game begins and in between rounds.

Sub Open()
me.top=0
me.left=0
me.width=screen(0).width
me.height=screen(0).height
End Sub

To get the game started, enter the code in Listing 5 into the Action Event of PushButton1.

Listing 5. The Action Event of PushButton1.

Sub Action
ClearAllSprites
InitSprites
SpriteSurface1.run
End Sub

If any sprites are still around from previous games, they are cleared by the ClearAllSprites method. Next all of the sprites are initialized with InitSprites and the game play begins by calling the Run method of SpriteSurface1.

The SpriteSurface

At the heart of REALbasic sprite animation is the SpriteSurface control. It is a bit of an unusual control in that it has a dual personality. It acts like a Canvas control drawing graphics in a similar fashion, while periodically executing code like a Timer. The FrameSpeed property of the SpriteSurface is the rate at which the timed functions of a SpriteSurface fire. To calculate the FrameSpeed, divide 60 by the desired frames per second and round up to an integer. For example, to achieve a speed 30 frames per second:

60 / 30 = 2 (the FrameSpeed)

A FrameSpeed of 0 (zero) is the fastest speed at which a SpriteSurface can draw. A setting of 1 or 2 is typical, depending on speed and complexity required. The Run method of SpriteSurface1 was called earlier in the PushButton1 Action event. This causes the SpriteSurface to periodically fire the NextFrame event at the FrameSpeed rate until the SpriteSurface1.close method is called. As the NextFrame event fires, we look at the current conditions of all of the sprites and change them if necessary. For example, it is in the NextFrame event where we check for keys being pressed. If a key is pressed, then some aspect of a sprite can be changed (e.g. position). REALbasic takes care of doing all the redrawing for us. We simply tell it where to draw.

Listing 5 shows the NextFrame event of SpriteSurface1. In it, you will notice some other things going on. First off, a scoreboard is drawn. The scoreboard is simply a string that displays the number of BadguySprites remaining. Behind this string is a small blue rectangle, which serves the purpose of erasing the number each time. The color blue is used, because it will also be the color of the entire background of the SpriteSurface. After redrawing the scoreboard, the code checks the keyboard for keys being pressed. It looks at the left, right, up, and down arrow keys, as well as the space bar. If any of them are depressed, appropriate actions are taken. One piece of code specific to the GunSprite here is ShootingSound.play. ShootingSound is a sound file that has been dragged into the project window. Be sure to make your sounds relatively short, because long sounds can impede smooth animation. Finally the BadGuySprites are moved.

Listing 5. The SpriteSurface1 NextFrame event.

Sub NextFrame()
dim i as integer
//draw the scoreboard
me.graphics.forecolor=rgb(0,0,100)
me.graphics.fillrect 150+leftEdge,467+topEdge,40,13
me.graphics.forecolor=rgb(255,255,255)
me.graphics.textfont="Geneva"
me.graphics.textsize=10
// ! put the following code all on one line !
me.graphics.drawstring "Bad Guys Remaining: " + str(NumOfBadGuys), 50+leftEdge,477+topEdge

if me.keyTest(123) then //check left arrow key 
//plane moves left
GoodGuySprite.x=GoodGuySprite.x-10
if GoodGuySprite.x<=0 then
GoodGuySprite.x=2
end if
end if
if me.keyTest(124) then //check right arrow key 
//plane moves right
GoodGuySprite.x=GoodGuySprite.x+10
if GoodGuySprite.x>600 then
GoodGuySprite.x=598
end if
end if
if me.keyTest(126) then //check up arrow key 
//plane moves up 
GoodGuySprite.y=GoodGuySprite.y-4
if GoodGuySprite.y<350 then
GoodGuySprite.y=350
end if
end if
if me.keyTest(125) then //check down arrow key 
//plane moves down
GoodGuySprite.y=GoodGuySprite.y+4
if GoodGuySprite.y>435 then
GoodGuySprite.y=435
end if
end if

if me.keyTest(49) then //fire=spacebar
//shoot the gun
ShootingSound.play
if gunvisible=false then
//init the gunfire position here
GunSprite.x=GoodGuySprite.x+12
GunSprite.y=GoodGuySprite.y
gunvisible=true
end if
end if

//now check the position of gun only if it's turned on
if gunvisible=true then
GunSprite.y=GunSprite.y-30
//if the gun has reached the top of the screen
//hide it again and turn it off
if GunSprite.y<0 then
GunSprite.x=-200
GunSprite.y=447
gunvisible=false
end if
end if
    
//advance the badguys  
for i=1 to 10
//this is the speed of descent (increase for faster movement)
BadguySprite(i).y=BadguySprite(i).y+5
//if we have reached the bottom of the screen
//go back up to the top at some random x position
if BadguySprite(i).y>447 then
BadguySprite(i).x=rnd*600
BadguySprite(i).y=40
end if
next

End Sub

So far, this code will produce a nice animation where the GoodguySprite can navigate and shoot at the approaching BadguySprites.

SpriteSurface Collisions

When a GunSprite hits a BadguySprite, nothing happens yet. Nor will anything occur if the BadguySprite manages to run into the GoodguySprite. This is the function of the SpriteSurface1 Collision Event. Listing 6 details the code for the SpriteSurface's Collision Event. This is where the Sprite Group numbers from earlier in this article become important. The Collision Event of a SpriteSurface is automatically passed the Group numbers of the sprites that have collided. In the event, we simply check to see which two sprites have collided and then take some action. In this example, we will only look at two types of collisions - both the GunSprite and BadguySprite have collided or the GoodguySprite and BadguySprite have collided. If the GunSprite has collided with a BadguySprite, then we close both of the sprites (in effect "killing" them), play a sound, decrease the number of NumOfBadGuys variable, and call RemakeGun for the next time a user fires the gun. We must also check to see if all of the BadguySprites have been killed. If so, then the game is over and the player has won. Finally, if a BadguySprite has managed to collide with the GoodguySprite then the game is over and the player has lost.

Listing 6. The Collision Event of SpriteSurface1.

Sub Collision (s1 as Sprite, s2 as Sprite)
//GunSprite and BadguySprite have collided
if s1.group=2 and s2.group=3 then
BadGuyCrashSound.play
s1.close
s2.close
RemakeGun // since we killed the gun sprite, init it again
NumOfBadGuys=NumOfBadGuys-1
if NumOfBadGuys=0 then
s1.close
s2.close
spritesurface1.close
Statictext1.text="You Win!"
CheeringSound.play
end if
end if

//GoodguySprite and BadguySprite have collided
if s1.group=1 and s2.group=3 then
s1.close
s2.close
spritesurface1.close
Statictext1.text="You Lose!"
GoodGuyCrashSound.play
end if
End Sub

To spice things up a little, it is often desirable to draw a background behind the game. The SpriteSurface background is broken up into a grid of 64x64 squares. The PaintTile event takes care of refreshing these background tiles. To fill the background with a solid blue color, enter this code into the PaintTile event of SpriteSurface1.

Sub PaintTile (g as Graphics, xpos as Integer, ypos as Integer)
g.forecolor=rgb(0,0,100)
g.fillrect 0,0,64,64
End Sub

Keep in mind that any standard graphics drawing can take place in the PaintTile event. The final step is to add some code to the Open event of SpriteSurface1. Like the Window1 Open event code, this code is strictly cosmetic. It has been adopted from code by Matt Neuberg in his book REALbasic: The Definitive Guide. It centers SpriteSurface1 on the screen.

Sub Open()
leftEdge = (Screen(0).width - 640) \ 2
topEdge = (Screen(0).height - 480) \ 2
me.surfaceleft = leftEdge + ((640-me.surfacewidth) \ 2)
me.surfacetop=topEdge
End Sub

Having completed the code, it is time to test the finished application. Select Debug:Run menu. Click PushButton1 and play the game. If something goes wrong, recheck your code for accuracy and make sure that you have added all of the necessary auxiliary files (the resource file and the sound files). If all else fails, you can download the finished source code from MacTech's web site.

Conclusions

In this article, we took a brief look at Sprites in REALbasic by constructing a game. The game could be upgraded in a number of ways. Hopefully, this article gives you some basic background about how to make some of these changes yourself. If you would like more information about game development on the Macintosh particularly with regard to REALbasic, be certain to check the Reference section at the end of this article.

References


Erick Tejkowski is still looking for a decent version of Moon Patrol[TM] for the Mac. You can reach him at ejt@norcom2000.com.

 
AAPL
$105.22
Apple Inc.
+0.39
MSFT
$46.13
Microsoft Corpora
+1.11
GOOG
$539.78
Google Inc.
-4.20

MacTech Search:
Community Search:

Software Updates via MacUpdate

OS X Server 4.0 - For OS X 10.10 Yosemit...
Designed for OS X and iOS devices, OS X Server makes it easy to share files, schedule meetings, synchronize contacts, develop software, host your own website, publish wikis, configure Mac, iPhone,... Read more
TotalFinder 1.6.12 - Adds tabs, hotkeys,...
TotalFinder is a universally acclaimed navigational companion for your Mac. Enhance your Mac's Finder with features so smart and convenient, you won't believe you ever lived without them. Tab-based... Read more
BusyCal 2.6.3 - Powerful calendar app wi...
BusyCal is an award-winning desktop calendar that combines personal productivity features for individuals with powerful calendar sharing capabilities for families and workgroups. BusyCal's unique... Read more
calibre 2.7 - Complete e-library managem...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital... Read more
Skitch 2.7.3 - Take screenshots, annotat...
With Skitch, taking, annotating, and sharing screenshots or images is as fun as it is simple.Communicate and collaborate with images using Skitch and its intuitive, engaging drawing and annotating... Read more
Delicious Library 3.3.2 - Import, browse...
Delicious Library allows you to import, browse, and share all your books, movies, music, and video games with Delicious Library. Run your very own library from your home or office using our... Read more
Art Text 2.4.8 - Create high quality hea...
Art Text is an OS X application for creating high quality textual graphics, headings, logos, icons, Web site elements, and buttons. Thanks to multi-layer support, creating complex graphics is no... Read more
Live Interior 3D Pro 2.9.6 - Powerful an...
Live Interior 3D Pro is a powerful yet very intuitive interior designing application. View Video Tutorials It has every feature of Live Interior 3D Standard, plus some exclusive ones: Create multi... Read more
The Hit List 1.1.7 - Advanced reminder a...
The Hit List manages the daily chaos of your modern life. It's easy to learn - it's as easy as making lists. And it's powerful enough to let you plan, then forget, then act when the time is right.... Read more
jAlbum Pro 12.2.4 - Organize your digita...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code!... Read more

Latest Forum Discussions

See All

Rami Ismail Opens Up distribute​() for D...
Rami Ismail Opens Up distribute​() for Developers Posted by Jessica Fisher on October 24th, 2014 [ permalink ] Rami Ismail, Chief Executive of Business and Development at indie game studio | Read more »
Great Hitman GO Goes on Sale and Gets Ne...
Great Hitman GO Goes on Sale and Gets New Update – Say That Three Times Fast Posted by Jessica Fisher on October 24th, 2014 [ permalink ] | Read more »
Rival Stars Basketball Review
Rival Stars Basketball Review By Jennifer Allen on October 24th, 2014 Our Rating: :: RESTRICTIVE BUT FUNUniversal App - Designed for iPhone and iPad Rival Stars Basketball is a fun mixture of basketball and card collecting but its... | Read more »
Rubicon Development Makes Over a Dozen o...
Rubicon Development Makes Over a Dozen of Their Games Free For This Weekend Only Posted by Jessica Fisher on October 24th, 2014 [ permalink ] | Read more »
I Am Dolphin Review
I Am Dolphin Review By Jennifer Allen on October 24th, 2014 Our Rating: :: NEARLY FIN-TASTICUniversal App - Designed for iPhone and iPad Swim around and eat nearly everything that moves in I Am Dolphin, a fun Ecco-ish kind of game... | Read more »
nPlayer looks to be the ultimate choice...
Developed by Newin Inc, nPlayer may seem like your standard video player – but is aiming to be the best in its field by providing high quality video play performance and support for a huge number of video formats and codecs. User reviews include... | Read more »
Fighting Fantasy: Caverns of the Snow Wi...
Fighting Fantasy: Caverns of the Snow Witch Review By Jennifer Allen on October 24th, 2014 Our Rating: :: CLASSY STORYTELLINGUniversal App - Designed for iPhone and iPad Fighting Fantasy: Caverns of the Snow Witch is a sterling... | Read more »
A Few Days Left (Games)
A Few Days Left 1.01 Device: iOS Universal Category: Games Price: $3.99, Version: 1.01 (iTunes) Description: Screenshots are in compliance to App Store's 4+ age rating! Please see App Preview for real game play! **Important: Make... | Read more »
Toca Boo (Education)
Toca Boo 1.0.2 Device: iOS Universal Category: Education Price: $2.99, Version: 1.0.2 (iTunes) Description: BOO! Did I scare you!? My name is Bonnie and my family loves to spook! Do you want to scare them back? Follow me and I'll... | Read more »
Intuon (Games)
Intuon 1.1 Device: iOS Universal Category: Games Price: $.99, Version: 1.1 (iTunes) Description: Join the battle with your intuition in a new hardcore game Intuon! How well do you trust your intuition? Can you find a needle in a... | Read more »

Price Scanner via MacPrices.net

Weekend sale: 13-inch 128GB MacBook Air for $...
Best Buy has the 2014 13-inch 1.4GHz 128GB MacBook Air on sale for $849.99, or $150 off MSRP, on their online store. Choose free home shipping or free local store pickup (if available). Price valid... Read more
Nimbus Note Cross=Platform Notes Utility
Nimbus Note will make sure you never forget or lose your valuable data again. Create and edit notes, save web pages, screenshots and any other type of data – and share it all with your friends and... Read more
NewerTech’s Snuglet Makes MagSafe 2 Power Con...
NewerTech has introduced the Snuglet, a precision-manufactured ring designed to sit inside your MagSafe 2 connector port, providing a more snug fit to prevent your power cable from unintentional... Read more
Apple Planning To Sacrifice Gross Margins To...
Digitimes Research’s Jim Hsiao says its analysts believe Apple is planning to sacrifice its gross margins to save its tablet business, which has recently fallen into decline. They project that Apple’... Read more
Who’s On Now? – First Instant-Connect Search...
It’s nighttime and your car has broken down on the side of the highway. You need a tow truck right away, so you open an app on your iPhone, search for the closest tow truck and send an instant... Read more
13-inch 2.5GHz MacBook Pro on sale for $949,...
Best Buy has the 13″ 2.5GHz MacBook Pro available for $949.99 on their online store. Choose free shipping or free instant local store pickup (if available). Their price is $150 off MSRP. Price is... Read more
Save up to $125 on Retina MacBook Pros
B&H Photo has the new 2014 13″ and 15″ Retina MacBook Pros on sale for up to $125 off MSRP. Shipping is free, and B&H charges NY sales tax only. They’ll also include free copies of Parallels... Read more
Apple refurbished Time Capsules available sta...
The Apple Store has certified refurbished Time Capsules available for up to $60 off MSRP. Apple’s one-year warranty is included with each Time Capsule, and shipping is free: - 2TB Time Capsule: $255... Read more
Textilus New Word, Notes and PDF Processor fo...
Textilus is new word-crunching, notes, and PDF processor designed exclusively for the iPad. I haven’t had time to thoroughly check it out yet, but it looks great and early reviews are positive.... Read more
WD My Passport Pro Bus-Powered Thunderbolt RA...
WD’s My Passport Pro RAID solution is powered by an integrated Thunderbolt cable for true portability and speeds as high as 233 MB/s. HighlightsOverviewSpecifications Transfer, Back Up And Edit In... Read more

Jobs Board

*Apple* Solutions Consultant - Apple Inc. (U...
…important role that the ASC serves is that of providing an excellent Apple Customer Experience. Responsibilities include: * Promoting Apple products and solutions Read more
Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Project Manager / Business Analyst, WW *Appl...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.