collisions

atlantico/atlantico.asm

@@ -8,6 +8,8 @@
 ;; Variables declared in RAM zero-page
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 .segment "ZEROPAGE"
+Collision:			.res 1			 ; 0 or 1, if 0 no collision, if 1, collisison
+
 Buttons:        .res 1       ; Pressed buttons (A|B|Sel|Start|Up|Dwn|Lft|Rgt)
 PrevButtons:    .res 1       ; Stores the previous buttons from the last frame
 
@@ -39,6 +41,11 @@ ParamYPos:      .res 1       ; Used as parameter to subroutine
 ParamTileNum:   .res 1       ; Used as parameter to subroutine
 ParamNumTiles:  .res 1       ; Used as parameter to subroutine
 ParamAttribs:   .res 1       ; Used as parameter to subroutine
+ParamRectX1:		.res 1			 ; Used as parameter to subroutine
+ParamRectY1:		.res 1			 ; Used as parameter to subroutine
+ParamRectX2:		.res 1			 ; Used as parameter to subroutine
+ParamRectY2:		.res 1			 ; Used as parameter to subroutine
+
 
 PrevOAMCount:   .res 1       ; Store the previous number of bytes that were sent to the OAM
 
@@ -327,6 +334,103 @@ EndRoutine:
     rts
 .endproc
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Subroutine to check collisions
+;; PARAMS: ParamXPos, ParamYPos (x and y of missile)
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+.proc CheckEnemyCollision
+  	txa
+  	pha                                    ; Push and save the X register in the stack
+  
+  	ldx #0
+  	stx Collision                          ; Collision = 0
+
+	EnemiesCollisionLoop:
+		cpx #MAX_ACTORS * .sizeof(Actor)
+		beq FinishCollisionCheck
+			lda ActorsArray+Actor::Type,x
+			cmp #ActorType::AIRPLANE
+			bne NextEnemy													; If not an airplane - skip to next enemy type
+
+			;; LOAD BOUNDING BOX X1,Y1,X2,Y2
+			lda ActorsArray+Actor::XPos,x        ; Bounding Box X1Y1
+			sta ParamRectX1
+			lda ActorsArray+Actor::YPos,y
+			sta ParamRectY1
+
+			lda ActorsArray+Actor::XPos,x        ; Bounding Box X2Y2
+			clc
+			adc #22                              ; Get right value of the airplane bounding box by adding 22
+			sta ParamRectX2
+
+			lda ActorsArray+Actor::YPos,y        ; Bottom of box by adding 8, one sprite tall
+			clc
+			adc #8
+			sta ParamRectY2
+
+			jsr IsPointInsideBoundingBox
+
+			lda Collision
+			beq NextEnemy
+				lda #ActorType::NULL
+				sta ActorsArray+Actor::Type,x
+				jmp FinishCollisionCheck
+
+	NextEnemy:
+		txa
+		clc
+		adc #.sizeof(Actor)
+		tax
+		jmp EnemiesCollisionLoop
+	
+FinishCollisionCheck:
+	pla
+	tax
+
+	rts
+.endproc
+
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Subroutine to check if a point is inside a bounding box.
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;  Params:
+;;	 (ParamXPos, ParamYPos) - coords to be tested
+;;	 (ParamRectX1,ParamRectY1,ParamRectX2,ParamRectY2) Are rectangle coords)
+;;  Output:
+;;	 Collision flag is either 1 or 0
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+.proc IsPointInsideBoundingBox
+	lda ParamXPos
+	cmp ParamRectX1
+	bcc PointIsOutside
+
+	lda ParamYPos
+	cmp ParamRectY1
+	bcc PointIsOutside
+
+	lda ParamXPos
+	cmp ParamRectX2
+	bcs PointIsOutside
+
+	lda ParamYPos
+	cmp ParamRectY2
+	bcs PointIsOutside
+
+	PointIsInside:
+		lda #1
+		sta Collision
+		jmp EndCollisionCheck
+
+	PointIsOutside:
+		lda #0
+		sta Collision
+	
+	EndCollisionCheck:
+		rts
+
+.endproc
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Subroutine to loop all actors and update them (position, velocity, etc.)
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -345,6 +449,27 @@ EndRoutine:
           lda #ActorType::NULL
           sta ActorsArray+Actor::Type,x ; Remove the missile from the array
         SkipMissile:
+
+			CheckCollision:
+				lda ActorsArray+Actor::XPos,x
+				clc
+				adc #3
+				sta ParamXPos                      ; Missile position to be checked X += 3
+
+				lda ActorsArray+Actor::YPos,y
+				clc
+				adc #1
+				sta ParamYPos                      ; Missile position to be checked Y += 1
+
+				jsr CheckEnemyCollision             ; Perform collision check between the missile and other enemy actor
+
+				lda Collision
+				beq NoCollisionFound
+					lda #ActorType::NULL
+					sta ActorsArray+Actor::Type,x
+				NoCollisionFound:
+
+
         jmp NextActor
       :