anti aliasing a bresenham line

[falcore20]

Hi,

I am trying to anti-alias a bresenham line. I have this code so far. My only problem is that for the two variables that are declared as double, i have some problems. When i get to the code:

invD = 1.0 / (2.0 * Sqr(du * du + dv * dv))
invD2du = 2.0 * (du * invD)

It becomes

invD = 1# / (2# * Sqr(du * du + dv * dv))
invD2du = 2# * (du * invD)

There are # signs instead of decimals. Then i get overflow errors. Does anyone know how to fix this, or if there is a better way to anti alias the bresenham line? This would help me tremendously. Thankyou.




dim uend As Integer
Dim uincr As Integer
Dim vincr As Integer
Dim addr As Integer
Dim incrS As Integer
Dim incrD As Integer
Dim twovdu As Integer

Dim invD As Double
Dim invD2du As Double

Dim du As Integer
Dim dv As Integer
Dim u As Integer
Dim v As Integer

addr = (y0 * 640 + x0) * 4
dx = x1 - x0
dy = y1 - y0

If Abs(dx) > Abs(dy) Then
du = Abs(dx)
dv = Abs(dy)
u = x1
v = y1
uincr = 4
vincr = 640 * 4
If dx < 0 Then
uincr = -uincr
End If

If dy < 0 Then
vincr = -vincr
End If

Else

du = Abs(dy)
dv = Abs(dx)
u = y1
v = x1
uincr = 640 * 4
vincr = 4
If dy < 0 Then
uincr = -uincr
End If

If dx < 0 Then
vincr = -vincr
End If
End If

uend = u + 2 * du
d = (2 * dv) - du
incrS = 2 * dv
incrD = 2 * (dv - du)
twovdu = 0
invD = 1.0 / (2.0 * Sqr(du * du + dv * dv))
invD2du = 2.0 * (du * invD)

Do

PSet (addr, twovdu * invD)
PSet (addr + vincr, invD2du - twovdu * invD)
PSet (addr - vincr, invD2du + twovdu * invD)

If d < 0 Then
twovdu = d + du
d = d + incrS
Else
twovdu = d - du
d = d + incrD
v = v + 1
addr = addr + vincr
End If
u = u + 1
addr = addr + uincr
Loop While (u < uend)

[dafhi]

the # means the computer is recognizing the number as a double. if you put 1.1, the # would disappear, however it is best to leave it because to my knowledge, any number without a type declaration following it is treated as a variant. 9! means single, 9# means double, 4& means Long, 4% means integer. The # most likely PREVENTS overflow, so the problem is that your calculations are going way over.