Creating Moving Graphics With the Sprite Routines

Creating Moving Graphics With the Sprite Routines
Drawing Moving Graphics With the Pic.Draw Command
Type the following program into the computer to produce moving graphics using the Pic.Draw predefined
procedures.
var spaceship, chair : int % Declares variables to store the spaceship and the chair graphics
spaceship := Pic.FileNew ("spaceship.bmp") % Creates a storage spot for the picture of the spaceship
chair := Pic.FileNew ("chair.gif") % Creates a storage spot for the picture of the chair
for i : 1 .. maxx by 50
Pic.Draw (spaceship, i, 100, picCopy)
Pic.Draw (chair, i, 300, picCopy)
delay (50)
end for
What is the problem with this program? What is causing this problem? Can you make a simple change to the
program above to make sure the “trail” does not appear?
Drawing Moving Graphics With Sprites
Turing 4.1 introduced sprites which has made working with graphics much easier. A sprite is a small graphic
that can be moved independently around the screen, producing animated effects. Turing 4.1 has a set of
predefined procedures and functions which allows the programmer to work with sprites. Using sprites
eliminates to need to draw and erase objects on the screen with the Pic.Draw procedure.
A sprite is created from a picture using the Sprite.New function. The sprite must then be shown on the screen
using the Sprite.Show procedure. The position of a sprite on the monitor can be defined using the
Sprite.SetPosition procedure. A sprite can be moved by changing its position again using Sprite.SetPosition.
The sprite at the original position will be automatically erased (restoring the background) and be redrawn at the
new location.
Multiple sprites can be created on the same window. They are each in different “layers” which allows them to
pass over/under each other. The layering of sprites is determined by the order of creation (the most recent ones
are higher) or by the Sprite.SetHeight procedure.
Learning Exercise #1 - Sprite.New, Sprite.Show, Sprite.SetPosition
Required: 1) Make sure the graphic files spaceship.bmp, chair.gif and airplane.bmp are in your Graphics
folder.
2) Input the following program to learn about the various Sprite predefined procedures and
functions.
% Moving sprites!
var chair, chairSprite : int % Declares variables to store the chair graphic and the chair sprite
chair := Pic.FileNew ("chair.gif") /* Creates a storage spot for the picture of the chair and stores it in the variable chair.*/
chairSprite := Sprite.New (chair) /* Creates a sprite from the picture of the chair and stores it in the variable chairSprite.
The parameter for this function is the variable storing the picture. */

Sprite.Show (chairSprite ) /* Makes the sprite appear in the window. The parameter for this procedure is the
variable storing the sprite. */
delay (1000)
Sprite.SetPosition (chairSprite , 0,0, false) /* Changes the position of the sprite. The parameter for this procedure is the
variable storing the sprite, the x and y position and a boolean value (true or
false) . If this value is true, then the sprite is centered on the x, y position.
Otherwise, the x, y position specifies the lower-left corner of the sprite.*/
delay (1000)
Sprite.SetPosition (chairSprite , 200,0, false) % Re-sets the position of the sprite
delay (1000)
Sprite.SetPosition (chairSprite , 0,200, false)
delay (1000)
Sprite.SetPosition (chairSprite , 200,200, false)
Learning Exercise #2 - Sprite.Height
1. Add the following code to your current program to create and show a sprite of a spaceship. The code will be
placed immediately after the corresponding commands to create, show and move the chair sprite.
var spaceship, spaceshipSprite :int % Declares variables to store the spaceship graphic and the spaceship sprite
spaceship := Pic.FileNew ("spaceship.bmp") /* Creates a storage spot for the picture of the chair and stores it in the
variable spaceship.*/
spaceshipSprite := Sprite.New (spaceship) /* Creates a sprite from the picture of the spaceship and stores it in the
variable spaceshipSprite. The parameter for this function is the variable
storing the picture. */
Sprite.Show (spaceshipSprite) /* Makes the sprite appear in the window. The parameter for this procedure is the
variable storing the sprite*/
Sprite.SetPosition (spaceshipSprite , 0,0, false) /* Changes the position of the sprite. The parameter for this procedure
is the variable storing the sprite, the x and y position and a boolean
value (true or false) . If this value is true, then the sprite is centered on
the x, y position. Otherwise, the x, y position specifies the lower-left
corner of the sprite.*/
Sprite.SetPosition (spaceshipSprite , 200,0, false) % Re-sets the position of the sprite
Sprite.SetPosition (spaceshipSprite , 0,200, false)
Sprite.SetPosition (spaceshipSprite , 200,200, false)
Note that the spaceship always ends up on top. Why?
2. After the code Sprite.SetPosition (spaceshipSprite , 0,200, false), add the following lines of code:
Sprite.SetHeight (chairSprite, 2) % Changes the order of the sprites
Sprite.SetHeight (spaceshipSprite, 1)
What happened? Why?
3. Change the order of the sprites back to the original order when they are drawn at position 200,200.