Lookup for render span VRAM rows

GenerateVRAMYOffset.py

@@ -5,7 +5,6 @@ import sys
 
 def main(argv):
 
-	# Prologue
 	print ("vramYOffset:",end="")
 	rowCount = 19
 	
@@ -19,6 +18,19 @@ def main(argv):
 		if (rowCount<19):
 			print (",", end="")
 
+	print ("\n\vramRowInvertedSpanLookup:",end="")
+	rowCount = 19
+	
+	for jump in range(0,200):
+		rowCount += 1
+		if (rowCount==20):
+			print ("\n\t.word ", end="")
+			rowCount=0
+		
+		print ("$%04x" % ((200-jump)*160+8192), end="")
+		if (rowCount<19):
+			print (",", end="")
+
 
 if __name__ == "__main__":
 	main(sys.argv[1:])

tables.s

@@ -152,4 +152,16 @@ vramYOffset:
 	.word $6400,$64a0,$6540,$65e0,$6680,$6720,$67c0,$6860,$6900,$69a0,$6a40,$6ae0,$6b80,$6c20,$6cc0,$6d60,$6e00,$6ea0,$6f40,$6fe0
 	.word $7080,$7120,$71c0,$7260,$7300,$73a0,$7440,$74e0,$7580,$7620,$76c0,$7760,$7800,$78a0,$7940,$79e0,$7a80,$7b20,$7bc0,$7c60
 
+vramRowInvertedSpanLookup:
+	.word $9d00,$9c60,$9bc0,$9b20,$9a80,$99e0,$9940,$98a0,$9800,$9760,$96c0,$9620,$9580,$94e0,$9440,$93a0,$9300,$9260,$91c0,$9120
+	.word $9080,$8fe0,$8f40,$8ea0,$8e00,$8d60,$8cc0,$8c20,$8b80,$8ae0,$8a40,$89a0,$8900,$8860,$87c0,$8720,$8680,$85e0,$8540,$84a0
+	.word $8400,$8360,$82c0,$8220,$8180,$80e0,$8040,$7fa0,$7f00,$7e60,$7dc0,$7d20,$7c80,$7be0,$7b40,$7aa0,$7a00,$7960,$78c0,$7820
+	.word $7780,$76e0,$7640,$75a0,$7500,$7460,$73c0,$7320,$7280,$71e0,$7140,$70a0,$7000,$6f60,$6ec0,$6e20,$6d80,$6ce0,$6c40,$6ba0
+	.word $6b00,$6a60,$69c0,$6920,$6880,$67e0,$6740,$66a0,$6600,$6560,$64c0,$6420,$6380,$62e0,$6240,$61a0,$6100,$6060,$5fc0,$5f20
+	.word $5e80,$5de0,$5d40,$5ca0,$5c00,$5b60,$5ac0,$5a20,$5980,$58e0,$5840,$57a0,$5700,$5660,$55c0,$5520,$5480,$53e0,$5340,$52a0
+	.word $5200,$5160,$50c0,$5020,$4f80,$4ee0,$4e40,$4da0,$4d00,$4c60,$4bc0,$4b20,$4a80,$49e0,$4940,$48a0,$4800,$4760,$46c0,$4620
+	.word $4580,$44e0,$4440,$43a0,$4300,$4260,$41c0,$4120,$4080,$3fe0,$3f40,$3ea0,$3e00,$3d60,$3cc0,$3c20,$3b80,$3ae0,$3a40,$39a0
+	.word $3900,$3860,$37c0,$3720,$3680,$35e0,$3540,$34a0,$3400,$3360,$32c0,$3220,$3180,$30e0,$3040,$2fa0,$2f00,$2e60,$2dc0,$2d20
+	.word $2c80,$2be0,$2b40,$2aa0,$2a00,$2960,$28c0,$2820,$2780,$26e0,$2640,$25a0,$2500,$2460,$23c0,$2320,$2280,$21e0,$2140,$20a0
+
 .include "circleTable.s"

terrain.s

@@ -130,15 +130,12 @@ renderTerrainRowSpans:
 	sta SCRATCHL			; Track span color
 
 	; Find VRAM row
-	lda #200
-	sec
-	sbc PARAML1
+	lda PARAML1
 	asl
 	tax
-	lda vramYOffset,x
-	clc
-	adc #$2000
+	lda vramRowInvertedSpanLookup,x
 	tax
+	
 	adc #160
 	sta PARAML0				; Watch for end of VRAM row