Game Development Reference
In-Depth Information
Figure 14-1. Features with this image require the Game Maker Pro edition.
Browse around to see what's here, and add those finishing touches to your game—or just try
them out to learn, to tinker, and to have fun.
360-Degree Movement
If you've read The Game Maker's Apprentice , you are probably familiar with one form of
360-degree movement, where you used a sprite with rotated subimages to move in any direction.
If you have Game Maker Pro, however, there is another, simpler way to rotate the sprite. We'll
create an Asteroids-like space ship to show you how.
Start with: Reference/Framework/spaceship1.gmk
Creating 360-Degree Movement
1. Open spr_spaceship and note that the sprite contains two subimages that we will use
to show and hide the jet flames. Click the Center button—this is important because a
sprite rotates around its origin!
2. Create a new object, call it obj_spaceship , and set the Sprite to spr_spaceship .
3. Add a Create event and insert the Set Variable action with Variable image_speed and
Value 0 . This stops the sprite from animating.
4. Add a Keyboard , <Left> event and include a Set Variable action with Variable
image_angle and Value 5 , Relative . This action rotates the sprite counter-clockwise.
5. Add a Keyboard , <Right> event and include a Set Variable action with Variable
image_angle and Value -5 , Relative . This action rotates the image clockwise.
6. Add a Keyboard , <Up> event and include a Move Free action. Set Direction to
image_angle and Speed to 0.2 . Check the Relative box.
7. In the same event, include a Set Variable action with Variable speed and Value
min(speed,6) . This keeps the speed limited to 6.
8. Add a Key Press , <Up> event and include a Set Variable action with Variable
image_index and Value 1 . This will show the subimage with a fired engine.
9. In the same event, include a Play Sound action for snd_engine . Set Loop to true .
10. Add a Key Release , <Up> event and include a Set Variable action with Variable
image_index and Value 0 . This returns to the subimage with the inactive engine.
11. In the same event, include a Stop Sound action for snd_engine .
 
 
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