base:hybrid_hardware_software_sprite_collision_detection
This code checks which sprite triggered the hardware sprite collision detection when bit 1 of $D01E is turned on. Assuming sprite 0 is the player sprite and sprites 1…7 are the “enemies”. A collision is considered TRUE if a sprite is within +/-20px on the Y axis and +/-23px on X axis from the player sprite. SPR_COLL_DETECT returns in .X the sprite number which is in that area. If multiple collisions are in “TRUE” condition, the higher sprite value is returned first. If you need to check multiple collisions, you should continue the SPR_COLL_DETECT code calling SPR_COLL_LOOP without altering .X register.
|----->---->----->---------->24 pixels | | | |___________ ################## | ################## | ################## | ################## | ######xxxxxx######____________|-> 21 pixels ######x****x###### | ######x****x###### | ######x****x###### | ######x****x######____________| ######xxxxxx###### |-> 21 pixels ################## | ################## | ################## | ##################____________| | | | | |----->----->----->---------->24 pixels # = Detect area around player sprite x = Overlayed player/enemies pixels for checking purposes * = Player sprite central pixels ;---------------------------------------
;--------------------------------------- ; Collisions detection ; Hybrid hardware/software collision ; detect code. ; By Flavioweb 2018. ;------------------- CHECK_PLR_COLLISION LDA $D01E AND #%00000001 ; Some HW detected collision with player sprite? BEQ CHECK_PLR_COLLISION_EXIT ; No -> Exit. JSR SPR_COLL_DETECT ; Check which sprite collided with player. BNE CHECK_PLR_SPRITE_01 ; If .X==$00 no collision detected (which is almost impossible...) CHECK_PLR_COLLISION_EXIT RTS CHECK_PLR_SPRITE_01 CPX #$01 ; Check if sprite X is in "collision area" BNE CHECK_PLR_SPRITE_02 ; No -> check next sprite ; Do something here... RTS CHECK_PLR_SPRITE_02 CPX #$02 BNE CHECK_PLR_SPRITE_03 ; Do something here... RTS CHECK_PLR_SPRITE_03 CPX #$03 BNE CHECK_PLR_SPRITE_04 ; Do something here... RTS CHECK_PLR_SPRITE_04 CPX #$04 BNE CHECK_PLR_SPRITE_05 ; Do something here... RTS CHECK_PLR_SPRITE_05 CPX #$05 BNE CHECK_PLR_SPRITE_06 ; Do something here... RTS CHECK_PLR_SPRITE_01 CPX #$06 BNE CHECK_PLR_SPRITE_07 ; Do something here... RTS CHECK_PLR_SPRITE_07 CPX #$07 BNE CHECK_PLR_SPRITE_EXIT ; Do something here... CHECK_PLR_SPRITE_EXIT RTS ;--------------------------------------- ; Sprite collided detect ; If .X<>$00 = Sprite collided with player ; Plr = spr $00 ; From $01 enemies sprites. ;------------------- SPR_COLL_DETECT LDX #$07 SPR_COLL_LOOP LDA SPRITEY,X ; Load Enemy Y position SEC SBC SPRITEY ; Subtract Player Y position BPL CHECK_Y_NO_MINUS EOR #$FF ; Invert result sign CHECK_Y_NO_MINUS CMP #$15 ; Check for enemy sprite distance Y BCS CHECK_PLR_NO_COLL LDA SPRITEX,X ; Load Enemy X position SEC SBC SPRITEX ; Subtract Player X position BPL CHECK_NO_MINUS EOR #$FF ; Invert result sign CHECK_NO_MINUS CMP #$17 ; Check for enemy sprite distance X LDA SPRITEMSB EOR SPRITEMSB,X SBC #$00 BCS CHECK_PLR_NO_COLL RTS CHECK_PLR_NO_COLL DEX ; Goes to next sprite/enemy BNE SPR_COLL_LOOP RTS ;--------------------------------------- ; Sprites data tables examples ;------------------- SPRITEY .BYTE $64, $80, $A0, $D0, $50, $70, $90, $A0 SPRITEX .BYTE $A0, $80, $A0, $D0, $50, $70, $90, $A0 SPRITEMSB .BYTE $00, $00, $00, $00, $00, $00, $00, $00 ;-------------------------------------------------------------------------------
base/hybrid_hardware_software_sprite_collision_detection.txt · Last modified: 2018-01-28 15:08 by flavioweb