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In this section we offer some articles, how to program some specific parts of a game or the TI92!
We will add articles, so revisit this section!
Displaying of a game map
Do you want to display a game map on your screen? For example, you plan a game like Soko92, a civilization clone, or whatever. Only problem is that you need a powerful map display function. Ok, we'll explain to you, how to display it, fast!
You need
* A spritetable (SPRMAKER, or our SpriteEditor from Wizard).
* A PutSprite routine (also availabel in one of these packages)
* A map ;-)
So first of all, we need a defined mapsize. The routine gets the mapsizes (X_SIZE, Y_SIZE) in the registers d0, d1. Then we need two relative coordinates (relative_x, relative_y) in d2, d3. Then the number of sprites in one y and x line in a predefined constant called SPRITES_PER_X_LINE, SPRITES_PER_Y_LINE. The routine will display the map in the upper left corner. Last but not least the routine needs a pointer to the map
Notice: The routine doesn't check the relative coordinates
The spritesize will be 16x16
So, now we define a pseudo code
MAP_ADDRESS = MAP_POINTER + X_SIZE * RELATIVE_Y + RELATIVE_X
CURRENT_X = CURRENT_Y = 0 Needed for the putsprite routine
LOOP
LOOP
CURRENT_SPRITE = *MAP_ADDRESS
Draw the sprite
CURRENT_X = CURRENT_X + 16
WHILE NOT SPRITES_PER_Y_LINE ARE DRAWN
MAP_ADDRESS = MAP_ADDRESS + X_SIZE - SPRITES_PER_XLINE
CURRENT_Y = CURRENT_Y + 16
CURRENT_X = 0
WHILE NOT SPRITES_PER_X_LINE ARE DRAWN
The parameters of the putsprite routine are explained later!
So this is our pseudocode, and now we need the 68k routine.
SPRITES_PER_X_LINE equ 20 ; Your map size
SPRITES_PER_Y_LINE equ 20
; void DrawMap (int MAP_X_SIZE, int MAP_Y_SIZE,
; int REL_X_COOR, int REL_Y_COOR,
; char *Map)
; Input:
; MAP_X_SIZE in d0
; MAP_Y_SIZE in d1
; REL_X_COOR in d2
; REL_Y_COOR in d3
; Map in a0
DrawMap:
movem.l d0-d7/a0-a6,-(a7)
; Build map address
mulu.w d0,d3
add.w d2,d3
lea 0(a0,d3.w),a0 ; Map address calculated
; Build offset
sub.w #SPRITES_PER_X_LINE,d0
neg.w d0
move.w #SPRITES_PER_X_LINE-1,d1 ; Loop counter
clr.wou d3 ; Reset x coordinate (putsprite)na
clr.w d4 ; Reset y coordinate etutsprite)
\DrawMap_X_Line_Loop:
move.w #SPRITES_PER_Y_LINE-1,d2 ; Loop counter
\DrawMap_Y_Line_Loop:
clr.w d5 ; Clear old d5
move.b (a0)+,d5 ; Sprite number in d5
bsr Put16x16Sprite ; Call routine
add.w #16,d3 ; New x coordinate
dbra.w d2,\DrawMap_Y_Line_Loop ; Sprites drawn (y line)?
clr.w d3 ; Reset x coordinate
add.w #16,d4 ; New y coordinate
lea 0(a0,d0.w),a0 ; Correct map pointer
dbra.w d1,\DrawMap_X_Line_Loop ; Sprites drawn (x line)?
movem.l (a7)+,d0-d7/a0-a6 ; Function cleanup
rts ; Return to the caller
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So this is one of an important routine for a game, we hope it'll help you
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