DXC Companion

Tutorial 1 Part 3

So far our sprite has been moving automatically by the program. We will now add code that will make the sprite move under our control.

Add the following lines of code to the project you created in part 2.

Add another global variable called "FRAME_NUM" then set it to equal 1. This variable will keep track of the current frame of the animation sequence.

Next turn off the animation so that the man isn't continually walking (Sprite Animate 1 Off).

Set Sprite_X to equal 288 so that it starts in the middle of the screen.

We now need to change the code inside the repeating loop so that the sprite only moves when a cursor key is pressed. Check for the left cursor key (If CursorLeft()), now decrement FRAME_NUM (FRAME_NUM = FRAME_NUM - 1) and change the animation sequence frame (SetSequenceFrame(1,FRAME_NUM)).

Check to see if the sequence has reached the end. and if it has, reset it.

Do the same again except check for the right cursor key and increment FRAME_NUM.

As we will be pressing the cursor keys we will need to change the Until statement to check for a specific keypress such as "q".

Your code should now look like this :

NOTE: If you do not wish to type the code below you may download or open this text file and simply copy and paste the code into your project.

//TUTORIAL 1 PART 3

//DEFINE VARIABLES
Global KEYPRESS$, SPRITE_X, FRAME_NUM

//DEFINE PROCEDURES
DefProc INIT_DISPLAY()
DefProc CREATE_SPRITES()

//---- START MAIN CODE ----

//CALL THE PROCEDURE TO CREATE THE SCREEN
INIT_DISPLAY()

//CALL THE PROCEDURE TO CREATE THE SPRITES
CREATE_SPRITES()

FRAME_NUM = 1 //START WITH FRAME ONE
Sprite Animate 1 Off //TURN OFF ANIMATION SO THAT WE CAN MANUALLY ANIMATE THE SPRITE
SPRITE_X = 288 //START THE SPRITE IN THE MIDDLE OF THE SCREEN

//START LOOP - THIS LOOP WILL REPEAT UNTIL A KEY IS PRESSED
Repeat

//HAS THE LEFT CURSOR BEEN PRESSED?

//GO TO THE PREVIOUS FRAME IN THE ANIMATION

//DECREMENT THE FRAME_NUM VARIABLE

//HAS THE SEQUENCE REACHED THE START?

//IF IT HAS THEN GO BACK TO THE END

//MOVE SPRITE #1 TO THESE CO-ORDS

//DECREMENT SPRITE_X

//IS THE SPRITE AT THE END OF THE SCREEN?

//IF SO, THEN MOVE SPRITE TO JUST OFF THE RIGHT SIDE

If CursorRight() Then //HAS THE RIGHT CURSOR BEEN PRESSED?

SetSequenceFrame(1,FRAME_NUM) //GO TO THE NEXT FRAME IN THE ANIMATION
FRAME_NUM = FRAME_NUM + 1 //INCREMENT THE FRAME_NUM VARIABLE

If FRAME_NUM > 30 Then //HAS THE SEQUENCE REACHED THE END?

//IF IT HAS THEN GO BACK TO THE START

EndIf

//MOVE SPRITE #1 TO THESE CO-ORDS

//INCREMENT SPRITE_X

//IS THE SPRITE AT THE END OF THE SCREEN?

//IF SO, THEN MOVE SPRITE TO JUST OFF THE LEFT SIDE

EndIf

Until KEYPRESS$ = "q"

//THE INIT_DISPLAY PROCEDURE CREATES A SCREEN AND A PLANE
Procedure INIT_DISPLAY()

//CREATE A MAP IN BANK 50

//CREATE A TILE USING A BACKGROUND IMAGE IN BANK 1

//CREATE PLANE 1 USING THE MAP IN BANK 50

//SET WHITE TO BE TRANSPARENT INSTEAD OF DEFAULT BLACK AS OUR SPRITE CONTAINS BLACK PIXELS

EndProc

//THIS PROCEDURE WILL CREATE THE SPRITE
Procedure CREATE_SPRITES()

//CREATE SPRITE #1 AT 288,208 USING THE SEQUENCE IN BANK 3

//ENABLE THE SPRITE

//NOW TURN ON THE SPRITE SYSTEM

EndProc

EndProg