_TITLE "Do the dots in disk look like they are spinning?" ' B+ 2019-01-12 'try an optical illusion saw on Internet
x0
= xmax
/ 2: y0
= ymax
/ 2: a24
= _PI(2 / 24): r
= 240 xs
= x0
+ r
* COS(a24
* i
) ys
= y0
+ r
* SIN(a24
* i
) xe
= x0
+ r
* COS(a24
* i
+ _PI) ye
= y0
+ r
* SIN(a24
* i
+ _PI) x
= x0
+ COS(a
+ _PI(i
/ 6)) * r
* COS(a24
* i
) y
= y0
+ COS(a
+ _PI(i
/ 6)) * r
* SIN(a24
* i
) fcirc x, y, 10
loopcnt = loopcnt + 1
'Steve McNeil's copied from his forum note: Radius is too common a name
RadiusError = -subRadius
X = subRadius
Y = 0
' Draw the middle span here so we don't draw it twice in the main loop,
' which would be a problem with blending turned on.
LINE (CX
- X
, CY
)-(CX
+ X
, CY
), , BF
RadiusError = RadiusError + Y * 2 + 1
LINE (CX
- Y
, CY
- X
)-(CX
+ Y
, CY
- X
), , BF
LINE (CX
- Y
, CY
+ X
)-(CX
+ Y
, CY
+ X
), , BF
X = X - 1
RadiusError = RadiusError - X * 2
Y = Y + 1
LINE (CX
- X
, CY
- Y
)-(CX
+ X
, CY
- Y
), , BF
LINE (CX
- X
, CY
+ Y
)-(CX
+ X
, CY
+ Y
), , BF