Here is JAL PolarToCartesian with 1 degree accuracy and byte based
lookup table
const byte SINLOOKUP[] = {0, 3, 8, 12, 17, 21, 26, 30, 35, 39, 43, 48,
52, 57,
61, 65, 70, 74, 78, 82, 87, 91, 95, 99, 103, 107, 111, 115, 119,
123, 127,
131, 135, 138, 142, 146, 149, 153, 157, 160, 164, 167, 170, 174,
177, 180,
183, 186, 189, 192, 195, 198, 201, 203, 206, 209, 211, 214, 216,
218, 221,
223, 225, 227, 229, 231, 233, 235, 236, 238, 240, 241, 242, 244,
245, 246,
247, 248, 249, 250, 251, 252, 253, 253, 254, 254, 254, 255, 255,
255, 255 }
-- 0 to 90 degrees in 1 degree steps
-- WARNING
-- Don't forget to to add 1 to lookup, apart from value zero !
-- use the SINLOOKUP cast to an sword +1, then divide expression by
256 when done.
-- fixed point Integer math
procedure PolarToCartesian(sword in radius, sword in angle, sword out
xPos, sword out yPos) is
--make sure works for ANY angle ...
While angle < -90 loop
angle = angle + 360
end Loop
While angle > 270 loop
angle = angle - 360
end Loop
If angle > -90 And angle < 0 Then
angle = angle + 90
xPos = sword(SINLOOKUP[angle]) + 1
yPos = -sword(SINLOOKUP[90 - angle]) - 1
ElsIf angle > 0 And angle < 90 Then
yPos = sword(SINLOOKUP[angle]) + 1
xPos = sword(SINLOOKUP[90 - angle]) + 1
ElsIf angle > 90 And angle < 180 Then
angle = angle - 90
xPos = -sword(SINLOOKUP[angle]) - 1
yPos = sword(SINLOOKUP[90 - angle]) + 1
ElsIf angle > 180 And angle < 270 Then
angle = angle - 180
xPos = -sword(SINLOOKUP[90 - angle]) - 1
yPos = -sword(SINLOOKUP[angle]) - 1
End If
Case angle of
0, 360:
xPos = radius
yPos = 0
90:
xPos = 0
yPos = radius
180:
xPos = -radius
yPos = 0
-90, 270:
xPos = 0
yPos = -radius
otherwise
xPos = xPos * radius / 256
yPos = yPos * radius / 256
End case
End procedure
Above is not tested!
The VB6 version below is working
Private Sub PolarToCartesian(ByVal radius As Integer, ByVal angle As
Integer, ByRef xPos As Integer, ByRef yPos As Integer)
Dim sinLookup As Variant
'apart from zero, all values are 1 less than actual to allow
storage in 1 byte each
sinLookup = Array(0, 3, 8, 12, 17, 21, 26, 30, 35, 39, 43, 48, 52,
57, 61, 65, 70, 74, 78, 82, 87, 91, 95, 99, 103, 107, 111, 115, 119,
123, 127, 131, 135, 138, 142, 146, _
149, 153, 157, 160, 164, 167, 170, 174, 177, 180, 183, 186, 189,
192, 195, 198, 201, 203, 206, 209, 211, 214, 216, 218, 221, 223, 225,
227, 229, _
231, 233, 235, 236, 238, 240, 241, 242, 244, 245, 246, 247, 248,
249, 250, 251, 252, 253, 253, 254, 254, 254, 255, 255, 255, 255)
'make sure works for ANY angle ...
Do While angle <= -90
angle = angle + 360
Loop
Do While angle >= 270
angle = angle - 360
Loop
If angle > -90 And angle < 0 Then
angle = angle + 90
xPos = sinLookup(angle) + 1
yPos = -sinLookup((90 - angle)) - 1
ElseIf angle > 0 And angle < 90 Then
yPos = sinLookup(angle) + 1
xPos = sinLookup((90 - angle)) + 1
ElseIf angle > 90 And angle < 180 Then
angle = angle - 90
xPos = -sinLookup(angle) - 1
yPos = sinLookup((90 - angle)) + 1
ElseIf angle > 180 And angle < 270 Then
angle = angle - 180
xPos = -sinLookup((90 - angle)) - 1
yPos = -sinLookup(angle) - 1
End If
Select Case angle
Case -90:
xPos = 0
yPos = -radius
Case 0:
xPos = radius
yPos = 0
Case 90:
xPos = 0
yPos = radius
Case 180:
xPos = -radius
yPos = 0
Case Else
xPos = xPos * radius \ 256
yPos = yPos * radius \ 256
End Select
End Sub
dim xOrg = 62
dim yOrg = 31
dim radius =31
Private Sub DrawClockFace(radius as Integer , xOrg as Integer, yOrg as
Integer)
Dim faceDots As Integer
Dim xPos As Integer
Dim yPos As Integer
LCD_Init
LCD_DrawRectangle xOrg, yOrg, 2, 2, True 'centre
'draw minutes dots
For faceDots = 0 To 59
PolarToCartesian radius, faceDots * 6, xPos, yPos
LCD_Plot xOrg + xPos, yOrg + yPos, True
Next
'draw hour squares
For faceDots = 0 To 11
PolarToCartesian radius, faceDots * 30, xPos, yPos
LCD_DrawRectangle xOrg + xPos, yOrg + yPos, 2, 2, True
Next
End Sub
> I multiplied the sin values by 4096 (maybe 256 is enough on smaller
> displays) to have an Integer lookup to do integer math with Radius.
> then divide result (power of 2 so a shift).
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