From 74ea0a13b9d884452a99fbfc270cedc9f48a5a21 Mon Sep 17 00:00:00 2001
From: Vince Weaver <vince@deater.net>
Date: Thu, 7 Jan 2021 13:55:01 -0500
Subject: [PATCH] rotozoom: minor optimization

---
 graphics/gr/rotozoom/c00_scrn_offsets.s | 10 ++++++++--
 graphics/gr/rotozoom/rotozoom.s         | 11 ++++++-----
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/graphics/gr/rotozoom/c00_scrn_offsets.s b/graphics/gr/rotozoom/c00_scrn_offsets.s
index 814e7f8a..02a5f7dc 100644
--- a/graphics/gr/rotozoom/c00_scrn_offsets.s
+++ b/graphics/gr/rotozoom/c00_scrn_offsets.s
@@ -1,10 +1,16 @@
-c00_scrn_offsets_l:
+common_offsets_l:
 	.byte	<$c00,<$c80,<$d00,<$d80,<$e00,<$e80,<$f00,<$f80
 	.byte	<$c28,<$ca8,<$d28,<$da8,<$e28,<$ea8,<$f28,<$fa8
 	.byte	<$c50,<$cd0,<$d50,<$dd0,<$e50,<$ed0,<$f50,<$fd0
 
-c00_scrn_offsets_h:
+scrn_c00_offsets_h:
 	.byte	>$c00,>$c80,>$d00,>$d80,>$e00,>$e80,>$f00,>$f80
 	.byte	>$c28,>$ca8,>$d28,>$da8,>$e28,>$ea8,>$f28,>$fa8
 	.byte	>$c50,>$cd0,>$d50,>$dd0,>$e50,>$ed0,>$f50,>$fd0
 
+
+gr_400_offsets_h:
+	.byte	>$400,>$480,>$500,>$580,>$600,>$680,>$700,>$780
+	.byte	>$428,>$4a8,>$528,>$5a8,>$628,>$6a8,>$728,>$7a8
+	.byte	>$450,>$4d0,>$550,>$5d0,>$650,>$6d0,>$750,>$7d0
+
diff --git a/graphics/gr/rotozoom/rotozoom.s b/graphics/gr/rotozoom/rotozoom.s
index 4b85c7fe..b6c1161e 100644
--- a/graphics/gr/rotozoom/rotozoom.s
+++ b/graphics/gr/rotozoom/rotozoom.s
@@ -12,6 +12,8 @@
 ;	$39e3e=237,118=4.22fps	add scrn address lookup table
 ;	$39fdf=237,535		add two scale multiplies
 ;	$39e17=237,079=4.22fps	change the init to also use multiply
+;	$39dc9=237,001=		change to use common lookup table (outside inner loop)
+
 
 CAL	= $B0
 CAH	= $B1
@@ -177,16 +179,15 @@ smc_even:
 	ldy	#$4c		; jmp					; 2
 smc_write:
 	sty	rplot3_smc						; 4
-	asl		; now even					; 2
 
 	tay								; 2
 
-	lda	gr_offsets,Y	; lookup low-res memory address		; 4
+	lda	common_offsets_l,Y	; lookup low-res memory address	; 4
 	sta	rplot1_smc+1						; 4
 	sta	rplot2_smc+1						; 4
 
 	clc								; 2
-	lda	gr_offsets+1,Y						; 4
+	lda	gr_400_offsets_h,Y					; 4
 	adc	DRAW_PAGE	; add in draw page offset		; 3
 	sta	rplot1_smc+2						; 4
 	sta	rplot2_smc+2						; 4
@@ -235,9 +236,9 @@ rotozoom_xloop:
 	; TODO: put these in zero page?
 	;	also we can share low bytes with other lookup
 
-	lda	c00_scrn_offsets_l,Y	; lookup low-res memory address	; 4
+	lda	common_offsets_l,Y	; lookup low-res memory address	; 4
         sta	BASL							; 3
-        lda	c00_scrn_offsets_h,Y					; 4
+        lda	scrn_c00_offsets_h,Y					; 4
         sta	BASH							; 3
 
 	; carry was set a bit before to low bit of YPH