Print circle one pixel at a time

I know the syntax for a circle which prints it on the screen instantly, but I would like to print a circle (of a given size and placement) one point or pixel at a time so you could see the circle being drawn. Then I could move an object around in a circle. How can I do this?

Sparky84

Declare Function SetPixel Lib "gdi32" Alias "SetPixel" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal crColor As Long) As Long

As for the coords to use, I dont remember the exact equation, you might look for it on google, or just dig up an old geomtry book :)

VB Code:

Radian = Angle * (3.1415926 / 180)
PixelX = CentreX + Cos(Radian) * Radius
PixelY = CentreY + Sin(Radian) * Radius

Remember, if you're going to be dealing natively in radians, you'll want to remove the first line.

I appreciate the 2 replies, but I can not print the circle one dot at a time with the declare or code shown to me - it didn't do anything. I would need the code that could make it work - do I need to dim anything - do I use PSet - I would need all the code and know just how to do it.

Sparky84

Well, do a loop with my code, with Angle being 0 to 359, maybe step .5 if you want to do it a bit more smoothly. Then use PSET with whatever colour you want, and PixelX and PixelY being the X and Y values.

To draw the circle slowly what I have so far is:
Dim Radian As Double, PixelX As Single, PixelY As Single, Angle As Single
Under MouseDown to activate it I have - For Angle = 0 To 359 Step 0.5
Radian = Angle * (3.1415926 / 180)
PixelX = CentreX + Cos(Radian) * Radius
PixelY = CentreY + Cos(Radian) * Radius
PSet (PixelX, PixelY)
Next Angle
In Form Load I have
CentreX = 100
CentreY = 100
I did this to get it away from the side.

All it does is print one dot in the upper - left of the form.
Still hoping to learn how to make this work.

Sparky84

Here you go:

VB Code:

Declare Function SetPixel Lib "gdi32" Alias "SetPixel" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal crColor As Long) As Long
 
Private Sub Form_MouseDown(...)
Dim Radian As Double, PixelX As Single, PixelY As Single, Angle As Double
 
For Angle = 0 To 359.5 Step 0.5
    Radian = Angle * (3.1415926 / 180)
    PixelX = CentreX + Cos(Radian) * Radius
    PixelY = CentreY + Sin(Radian) * Radius
    SetPixelV Picture1.hDC, PixelX, PixelY, RGB(0, 0, 0)
Next Angle
 
End Sub
 
Private Sub Form_Load()
    CentreX = 100
    CentreY = 100
    Radius = 50
End Sub

I think that will work. Look at what I've changed, it'll help you to figure out where you went wrong.