Add rounding to sin/cos calc to improve accuracy

src/libsrc/sincos.pla

@@ -1,13 +1,16 @@
 include "inc/cmdsys.plh"
 include "inc/int32.plh"
 
-byte sin90hi[]
-byte = $00,$04,$09,$0D,$12,$16,$1B,$1F,$23,$28,$2C,$31,$35,$39,$3E,$42
-byte = $46,$4B,$4F,$53,$57,$5B,$60,$64,$68,$6C,$70,$74,$78,$7C,$7F,$83
-byte = $87,$8B,$8F,$92,$96,$99,$9D,$A0,$A4,$A7,$AB,$AE,$B1,$B4,$B7,$BA
-byte = $BE,$C0,$C3,$C6,$C9,$CC,$CE,$D1,$D3,$D6,$D8,$DB,$DD,$DF,$E1,$E3
-byte = $E5,$E7,$E9,$EB,$EC,$EE,$F0,$F1,$F3,$F4,$F5,$F6,$F7,$F8,$F9,$FA
-byte = $FB,$FC,$FD,$FD,$FE,$FE,$FE,$FF,$FF,$FF
+word sin90[]
+word = $0000,$0478,$08EF,$0D66,$11DC,$1650,$1AC2,$1F33,$23A1,$280C
+word = $2C74,$30D9,$353A,$3996,$3DEF,$4242,$4690,$4AD9,$4F1C,$5358
+word = $578F,$5BBE,$5FE6,$6407,$6820,$6C31,$7039,$7439,$782F,$7C1C
+word = $8000,$83DA,$87A9,$8B6D,$8F27,$92D6,$9679,$9A11,$9D9C,$A11B
+word = $A48E,$A7F3,$AB4C,$AE97,$B1D5,$B505,$B827,$BB3A,$BE3F,$C135
+word = $C41B,$C6F3,$C9BB,$CC73,$CF1C,$D1B4,$D43C,$D6B3,$D91A,$DB6F
+word = $DDB4,$DFE7,$E209,$E419,$E617,$E804,$E9DE,$EBA6,$ED5C,$EEFF
+word = $F090,$F20E,$F378,$F4D0,$F615,$F747,$F865,$F970,$FA68,$FB4C
+word = $FC1C,$FCD9,$FD82,$FE18,$FE99,$FF07,$FF60,$FFA6,$FFD8,$FFF6
 
 def sin32(deg)#0
     word[2] i32
@@ -15,22 +18,22 @@ def sin32(deg)#0
     while deg >= 360; deg = deg - 360; loop
     while deg < 0; deg = deg + 360; loop
     if deg < 90
-        i32[0] = ((sin90hi[deg] << 8) | sin90hi[deg])
+        i32[0] = (sin90[deg])
         i32[1] = 0
     elsif deg == 90
         i32[0] = 0
         i32[1] = 1
     elsif deg <= 180
-        i32[0] = ((sin90hi[180 - deg] << 8) | sin90hi[180 - deg])
+        i32[0] = (sin90[180 - deg])
         i32[1] = 0
     elsif deg < 270
-        i32[0] = -((sin90hi[deg - 180] << 8) | sin90hi[deg - 180])
+        i32[0] = -(sin90[deg - 180])
         i32[1] = -1
     elsif deg == 270
         i32[0] = 0
         i32[1] = -1
     else
-        i32[0] = -((sin90hi[360 - deg] << 8) | sin90hi[360 - deg])
+        i32[0] = -(sin90[360 - deg])
         i32[1] = -1
     fin
     load32(@i32)
@@ -40,6 +43,7 @@ export def mulsin(val, deg)
     word[2] i32
     sin32(deg)
     muli16(val)
+    addi16($7FFF) // Round up
     store32(@i32)
     return i32[1]
 end
@@ -48,6 +52,7 @@ export def mulcos(val, deg)
     word[2] i32
     sin32(deg + 90)
     muli16(val)
+    addi16($7FFF) // Round up
     store32(@i32)
     return i32[1]
 end

src/scripts/hrturtle.4th

@@ -9,7 +9,7 @@ SRC" TURTLE.4TH"
 : SHOW
   0 HGRMODE HGRDRAWBUF TILEDRAWBUF DROP
   280 192 INITTURTLE
-  1 HGRCOLOR
+  3 HGRCOLOR
 ;
 
 : SQUARE
@@ -20,7 +20,7 @@ SRC" TURTLE.4TH"
 ;
 
 : SPIN
-    360 0 DO
+    361 0 DO
         50 SQUARE
         I TURNTO
     10 +LOOP
@@ -30,3 +30,5 @@ SRC" TURTLE.4TH"
     SHOW
     SPIN
 ;
+
+SHOW SPIN