Snippet:Multiblit - Revision history

E5frog at 23:21, 15 November 2024

2024-11-15T23:21:24Z

E5frog at 21:09, 19 May 2020

2020-05-19T21:09:18Z

E5frog at 20:57, 19 May 2020

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E5frog at 20:55, 19 May 2020

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E5frog at 13:10, 14 May 2020

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E5frog at 12:59, 14 May 2020

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E5frog at 13:01, 25 August 2019

2019-08-25T13:01:59Z

E5frog at 13:00, 25 August 2019

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E5frog at 12:56, 25 August 2019

2019-08-25T12:56:43Z

E5frog: 1 revision

2012-11-16T21:23:46Z

1 revision

@@ Line 172: / Line 172: @@
 	lr	6, A							; save it
-	lis	1							; Same delay as in blit
+	lis	2							; Small delay
 .multiblitSavePixelDelay:
 	ai	$ff

@@ Line 1: / Line 1: @@
-The '''multiblit''' subroutine is a derivative of the '''[[Snippet:Blit|blit]]''' subroutine, but draws the image to the screen in four colors (2 bits per pixel).  The two-bit combination for green is %00, for red is %01, for blue is %10, and for the background color it's %11. Four pixels can be stored in a single byte of graphics data.
+The '''multiblit''' subroutine is a derivative of the '''[[Snippet:Blit|blit]]''' subroutine, but draws the image to the screen in four colors (2 bits per pixel). The two-bit combination for green is %00, for red is %01, for blue is %10, and for the background color it's %11. Four pixels can be stored in a single byte of graphics data.
-The parameters and instructions for the routines are almost the same, using '''multiblit''' instead of '''blit''' and '''MultiBlitGraphic''' instead of '''blitGraphic'''. All you need to do is to skip the two color bytes in the parameter data.
+The parameters and instructions for the routines are almost the same, using '''multiblit''' instead of '''blit''' and '''MultiBlitGfx''' instead of '''blitGraphic'''. All you need to do is to skip the two color bytes in the parameter data.
-To call the functions, you should use:
+To call the functions, you should use this for '''MultiBlitGfx''':
 <pre>
-	dci	graphic.parameters	; address of parameters
+	dci	gfx.parameters	; address of parameters
-	pi	multiblitGraphic
+	pi	MultiBlitGfx
 </pre>
-for '''multiblitGraphic''', and:
+Parameters can be stored where you like, it has the address for the actual gfx data, that can also be placed where convenient.
 <pre>
-	; parameters have been loaded into r1-r4 beforehand
+gfx.data:
-	dci	graphic.data		; address of graphic data
+	.byte	%00001010, %11000010, %11000010, %11000011, %00001010
 </pre>
-for '''multiblit'''. If you're using parameters stored in ROM, they should be in this order:
+If you want to use '''multiblit''' directly, make sure you have setup these data:
 <pre>
-graphic.parameters:
+r1 = x position
-	.byte	4			; x position
+r2 = y position
-	.byte	18			; y position
+r3 = width
-	.byte	$60			; width
+r4 = height
-	.byte	$13			; height
+DC = pointer to graphics
 </pre>
@@ Line 42: / Line 44: @@
+;
 ;-------------------;
-; Multiblit Graphic ;
+; MultiBlitGfx ;
 ;-------------------;
@@ Line 50: / Line 52: @@
 ; modifies: r1-r4, Q, DC
-MultiBlitGraphic:
+MultiBlitGfx:
 	; set ISAR
 	lisu	0

@@ Line 72: / Line 72: @@
 	; call the blit function
-	jmp	multiblit
+;	jmp	multiblit					; Not needed, it's the next piece of code
 ;--------------------;

@@ Line 1: / Line 1: @@
-The '''multiblit''' subroutine is a derivative of the '''[[Snippet:Blit|blit]]''' subroutine, but draws the image to the screen in four colors (2 bits per pixel).  The two-bit combination for green is %00, for red is %01, for blue is %10, and for the background color is %11. Four pixels can be stored in a single byte of graphics data.
+The '''multiblit''' subroutine is a derivative of the '''[[Snippet:Blit|blit]]''' subroutine, but draws the image to the screen in four colors (2 bits per pixel).  The two-bit combination for green is %00, for red is %01, for blue is %10, and for the background color it's %11. Four pixels can be stored in a single byte of graphics data.
 The parameters and instructions for the routines are almost the same, using '''multiblit''' instead of '''blit''' and '''MultiBlitGraphic''' instead of '''blitGraphic'''. All you need to do is to skip the two color bytes in the parameter data.
@@ Line 79: / Line 79: @@
+;
 ; Adjusted so that (0,0) is the top left pixel in the MESS display.
 ; If you want to skip this adjustment, saving 6 cycles, use
-; "multiblit_no".
+; "multiblit_no" for real origo - and not (4,4).
+;
-; this function blits a 4-color graphic based on parameters set
+; This function blits a 4-color graphic based on parameters set
 ; in r1-r4 and the graphic data pointed to by DC0, onto the
 ; screen
-; originally from cart 26, modified for color and annotated
+; Origin from cart 26, modified for color and annotated
+;
 ; modifies: r0-r7, DC
@@ Line 93: / Line 91: @@
 ; register reference:
 ; -------------------
 ; r1 = x position
 ; r2 = y position
@@ Line 113: / Line 112: @@
 	as	2
 	lr	2, A
 	lis	1
-	lr	7, A						; load #1 into r7 so it'll be reset when we start
+	lr	7, A							; load #1 into r7 so it'll be reset when we start
-	lr	A, 2						; load the y offset
+	lr	A, 2							; load the y offset
-	com							; invert it
+	com								; invert it
 .multiblitRow:
-	outs	5						; load accumulator into port 5 (row)
+	outs	5							; load accumulator into port 5 (row)
 	; check vertical counter
-	ds	4						; decrease r4 (vertical counter)
+	ds	4							; decrease r4 (vertical counter)
 	bnc	.multiblitExit					; if it rolls over exit
@@ Line 130: / Line 132: @@
 	lr	5, A
-	lr	A, 1						; load the x position
+	lr	A, 1							; load the x position
-	com							; complement it
+	com								; complement it
 .multiblitColumn:
-	outs	4						; use the accumulator as our initial column
+	outs	4							; use the accumulator as our initial column
 	; check to see if this byte is finished
-	ds	7						; decrease r7 (pixel counter)
+	ds	7							; decrease r7 (pixel counter)
 	bnz	.multiblitDrawPixel				; if we aren't done with this byte, branch
@@ Line 141: / Line 143: @@
 	; get the next graphics byte and set related registers
 	lis	4
-	lr	7, A						; load #4 into r7 (pixel counter)
+	lr	7, A							; load 4 into r7 (4 doublebit, pixel counter)
 	lm
-	lr	6, A						; load a graphics byte into r6
+	lr	6, A							; load a graphics byte into r6
 .multiblitDrawPixel:
 	; get new color
-	lr	A, 6						; Only keep b7 b6
+	lr	A, 6
-	sr	4
+	ni	%11000000						; Just keep top two
-	sr	1
+	outs	1							; output A in p1 (color)
 .multiblitTransferData:
 	; transfer the pixel data
-	li	$60
+	lis	6
 	outs	0
-	li	$c0
+	sl	1
 	outs	0
-	; and delay a little bit
 .multiblitSavePixelDelay:
-	ai	$60						; add 96
+	ai	$ff
 	bnz	.multiblitSavePixelDelay			; loop if not 0 (small delay)
 .multiblitCheckColumn:
-	ds	5						; decrease r5 (horizontal counter)
+	ds	5							; decrease r5 (horizontal counter)
 	bz	.multiblitCheckRow				; if it's 0, branch
-	ins	4						; get p4 (column)
+	ins	4							; get p4 (column)
-	ai	$ff						; add 1 (complemented)
+	as	0							; add 1 (complemented)
-	br	.multiblitColumn				; branch
+	br	.multiblitColumn					; branch
 .multiblitCheckRow:
-	ins	5						; get p5 (row)
+	ins	5							; get p5 (row)
-	ai	$ff						; add 1 (complemented)
+	as	0							; add 1 (complemented)
 	br	.multiblitRow					; branch

@@ Line 81: / Line 81: @@
 ; Full screen starts at (-4;-4) or you can remove the
 ; three row "fix"es below for faster display.
+; If you want to skip this adjustment, saving 6 cycles, use
+;
 ; this function blits a 4-color graphic based on parameters set
@@ Line 113: / Line 114: @@
 	lr	2, A
 	lis	1
 	lr	7, A						; load #1 into r7 so it'll be reset when we start
@@ Line 145: / Line 147: @@
 .multiblitDrawPixel:
 	; get new color
-	lr	A, 6
+	lr	A, 6						; Only keep b7 b6
 	sr	4
 	sr	1
@@ Line 154: / Line 156: @@
 	lr	A, 6						; load r6 (graphics byte)
 	sl	1
-	sl	1						; shift left two
+	sl	1						; shift left two, new bits on b7 b6
 	lr	6, A						; save it
@@ Line 162: / Line 164: @@
 	ds	0
 	bnc	.multiblitGetColorEnd
-	ai	$40						; multiply color number by $40
+	ai	$40						; add $40 to color number
 	br	.multiblitGetColor
 .multiblitGetColorEnd:
@@ Line 196: / Line 198: @@
 </pre>
-<em>Note: the adjustment of x and y in '''multiblit''' are to allow the coodinates 0, 0 to access the upper left pixel </em>visible to the screen<em>, not to VRAM, which expands four pixels above and to the left of that pixel.</em>
+<em>Note: the adjustment of x and y in '''multiblit''' are to allow the coodinates 0, 0 to access the upper left pixel </em>visible to the screen in MESS<em>, not to VRAM, which expands four pixels above and to the left of that position.</em>

@@ Line 36: / Line 36: @@
 ;================;
+;
-; green: %00
+; green: %00 (Port color code %00000000 / $00)
-; red  : %01
+; red  : %01 (Port color code %01000000 / $40)
-; blue : %10
+; blue : %10 (Port color code %10000000 / $80)
-; background: %11.
+; background: %11.  (Port color code %11000000 / $C0)
+;
 ;-------------------;

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