VB icon

Another Star Field (updated!) - well documented

Email
Submitted on: 1/2/2015 2:48:00 PM
By: Jeff Godfrey (from psc cd)  
Level: Not Given
User Rating: By 4 Users
Compatibility: VB 5.0, VB 6.0
Views: 1265
 
     Draws an animated StarField. A left-click with the mouse will move the StarField center to the mouse position, holding down the left mouse button while dragging the mouse will continually change the StarField center, holding down the right mouse button will activate a "hyperspace" effect (of sorts). The form can be resized. Each star's size and brightness is calculated according to its relative distance from you, the viewer. The number of stars in the StarField is easily changed.
 
code:
Can't Copy and Paste this?
Click here for a copy-and-paste friendly version of this code!
				
'**************************************
' Name: Another Star Field (updated!) - well documented
' Description:Draws an animated StarField. A left-click with the mouse will move the StarField center to the mouse position, holding down the left mouse button while dragging the mouse will continually change the StarField center, holding down the right mouse button will activate a "hyperspace" effect (of sorts). The form can be resized. Each star's size and brightness is calculated according to its relative distance from you, the viewer. The number of stars in the StarField is easily changed.
' By: Jeff Godfrey (from psc cd)
'
' Assumes:(1) Start a new project (2) Add a "timer" object to the existing form and set its "interval" property to "1" (3) Paste the supplied code into the Form code-window (4) Run it (5) Enjoy! (6) Notes: The vortex center can be changed by left-clicking with the mouse (or dragging the mouse with left button down) and the form can be resized, A HyperSpace effect (of sorts) can be activated by holding down the right mouse button, The number of stars can be changed by modifying the value of "gStarCount". "Submitting" this code seems to screw up its format (alignment and such), sorry....
'**************************************

Option Explicit
' Define a Star
Private Type StarType
xs As Long' X start coordinate
ys As Long' Y start coordinate
xe As Long' X end coordinate
ye As Long' Y end coordinate
Speed As Single' Star speed
End Type
'Number of Stars in the StarField
Const gStarCount = 150
' Define a "StarField" as a certain number of "Stars"
Dim StarField(gStarCount) As StarType
Dim gXCen As Long ' x center of vortex
Dim gYCen As Long ' y center of vortex
Dim gXVortexLow As Long' left most edge of vortex
Dim gXVortexHigh As Long' right most edge of vortex
Dim gYVortexLow As Long' top edge of vortex
Dim gYVortexHigh As Long' bottom edge of vortex
Dim gMaxRad As Long' used to adjust star "brightness"
Dim gHyperSpace As Boolean ' used to toggle hyperspace mode
Private Sub Form_Load()
' assign several Form properties
Me.BackColor = vbBlack
Me.Caption = "StarField - Jeff Godfrey"
Me.Show
Me.WindowState = vbMaximized
' assign vortex center to be the form center
GetNewVortex Me.ScaleWidth / 2, Me.ScaleHeight / 2
' initialize all Star objects
InitStars
End Sub
' initialize all Star objects
Sub InitStars()
Dim i As Integer
For i = 1 To gStarCount
' assign locations and speeds to all Stars in the StarField
StarField(i).xs = (gXVortexHigh - gXVortexLow - 1) * Rnd + gXVortexLow
StarField(i).ys = (gYVortexHigh - gYVortexLow - 1) * Rnd + gYVortexLow
StarField(i).xe = StarField(i).xs
StarField(i).ye = StarField(i).ys
StarField(i).Speed = Rnd + 0.1 ' (.1 - 1.1)
Next i
End Sub
' if the left mouse button was clicked, reassign vortex center
' to mouse location...
' if the right mouse button was clicked, activate
' "hyperspace" mode
Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
If (Button = vbLeftButton) Then
GetNewVortex X, Y
ElseIf (Button = vbRightButton) Then
gHyperSpace = True
End If
End Sub
' If the mouse is moved with the left button held down,
' continually change the vortex center
Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
If (Button = vbLeftButton) Then
GetNewVortex X, Y
End If
End Sub
' if the right button was just released...
' deactivate hyperspace mode and erase the hyperspace effect
Private Sub Form_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
If (Button = vbRightButton) Then
gHyperSpace = False
Me.Cls
End If
End Sub
' if the form is resized, reassign the vortex center to the new window center
Private Sub Form_Resize()
' recalculate new vortex information based on current form dimensions
GetNewVortex Me.ScaleWidth / 2, Me.ScaleHeight / 2
' if window is minimized or maximized, don't resize it
' (this will prevent a RunTime error...)
If (Me.WindowState = vbMaximized) Then Exit Sub
If (Me.WindowState = vbMinimized) Then Exit Sub
' ensure form is not made too small - this will
' prevent a possible "divide by 0" error...
If Me.Width < 500 Then Me.Width = 500
If Me.Height < 1500 Then Me.Height = 1500
End Sub
' Assign new vortex and other misc variables
' input: The X,Y coordinates of the new vortex center
' output: Nothing (reassigns global vortex variables)
Sub GetNewVortex(ByVal VortexgXCen As Long, ByVal VortexgYCen As Long)
Dim XOffset As Long ' a +/- X range from the vortex center
Dim YOffset As Long ' a +/- Y range from the vortex center
gXCen = VortexgXCen' the GLOBAL center of the vortex
gYCen = VortexgYCen' the GLOBAL center of the vortex
' calculate a range distance from the vortex center.
XOffset = Int(Me.Width * 0.1)
YOffset = Int(Me.Height * 0.1)
' calculate the GLOBAL actual range for both axis'
' a new star will always be "born" within this area...
gXVortexLow = gXCen - XOffset
gXVortexHigh = gXCen + XOffset
gYVortexLow = gYCen - YOffset
gYVortexHigh = gYCen + YOffset
' Assign a GLOBAL "maximum screen radius". This is
' used in the Star's brightness calculation
If (Me.ScaleWidth < Me.ScaleHeight) Then
gMaxRad = Int(Me.ScaleWidth / 2)
Else
gMaxRad = Int(Me.ScaleHeight / 2)
End If
End Sub
' when the timer fires, animate each Star in the StarField
' this is where all the interesting stuff happens...
Private Sub Timer1_Timer()
Dim i As Integer
Dim XVector As Long' current Star's X distance from "vortex" center
Dim YVector As Long' current Star's Y distance from "vortex" center
Dim NewXe As Long ' New X end coord of current Star
Dim NewYe As Long ' New Y end coord of current Star
Dim NewXs As Long ' New X start coord of current Star
Dim NewYs As Long ' New Y start coord of current Star
Dim Speed As Single' Speed of current Star
Dim Range As Integer ' Range of current Star
Dim DrawColor As Integer ' Color of current Star
Dim EraseColor As Integer ' Erase color (the form's background color)
' assign the erase color to be the form background color
EraseColor = Me.BackColor
 
' for each Star in the StarField...
For i = 1 To gStarCount
 
' set new startpoint equal to the Star's previous endpoint
NewXs = StarField(i).xe
NewYs = StarField(i).ye
Speed = StarField(i).Speed
' calculate X and Y distances from the current "vortex" center
XVector = Abs(gXCen - NewXs)
YVector = Abs(gYCen - NewYs)
' calculate Star's X direction and length based on current "vortex" X center
If (NewXs > gXCen) Then
NewXe = NewXs + Int(XVector * 0.2) * Speed
Else
NewXe = NewXs - Int(XVector * 0.2) * Speed
End If
' calcuate Star's Y direction and length based on current "vortex" Y center
If (NewYs > gYCen) Then
NewYe = NewYs + Int(YVector * 0.2) * Speed
Else
NewYe = NewYs - Int(YVector * 0.2) * Speed
End If
' if not in hyperspace mode...
' erase previous copy of the current Star (draw in backcolor)
If (Not gHyperSpace) Then
Me.Line (StarField(i).xs, StarField(i).ys)- _
(StarField(i).xe, StarField(i).ye), EraseColor
End If
' if new start coord is off the screen, reset it "near" the "vortex" center
If (NewXs < 0 Or NewXs > Me.ScaleWidth Or _
NewYs < 0 Or NewYs > Me.ScaleHeight) Then
StarField(i).xs = (gXVortexHigh - gXVortexLow - 1) * Rnd + gXVortexLow
StarField(i).ys = (gYVortexHigh - gYVortexLow - 1) * Rnd + gYVortexLow
StarField(i).xe = StarField(i).xs
StarField(i).ye = StarField(i).ys
' if new start coord is on the screen, draw new Star vector
Else
 
' see how far the Star is from the "vortex" center
' this is used to determine its "brightness"...
Range = GetStarRange(NewXs, NewYs)
DrawColor = Range * 25
' draw the Star at its new location
' the Star color can be changed here (currently yellow...)
Me.Line (NewXs, NewYs)-(NewXe, NewYe), RGB(DrawColor, DrawColor, 0)
' store Star endpoints for next erase cycle...
StarField(i).xs = NewXs
StarField(i).ys = NewYs
StarField(i).xe = NewXe
StarField(i).ye = NewYe
End If
Next i
End Sub
' determine how far the Star is from the "vertex" center
' used to determine the Star's brightness
' Note: Since this routine is called within the main animation
'loop, it is VERY EXPENSIVE (in CPU cycles) due the
'muliply, divide, and square root math. There should
'be a better way, but this will work for now...
' Input: X and Y coordinate of current star
' Output: An integer in the range of 1-10
Function GetStarRange(ByVal X As Long, ByVal Y As Long) As Integer
Dim Dist As Long
Dim XVector As Long
Dim YVector As Long
XVector = Abs(gXCen - X)
YVector = Abs(gYCen - Y)
' Calculate distance from "vortex" center
Dist = Sqr(XVector * XVector + YVector * YVector)
' return value in the range of 1-10
GetStarRange = Int((Dist / gMaxRad) * 10)
If (GetStarRange < 1) Then GetStarRange = 1
If (GetStarRange > 10) Then GetStarRange = 10
End Function


Report Bad Submission
Use this form to tell us if this entry should be deleted (i.e contains no code, is a virus, etc.).
This submission should be removed because:

Your Vote

What do you think of this code (in the Not Given category)?
(The code with your highest vote will win this month's coding contest!)
Excellent  Good  Average  Below Average  Poor (See voting log ...)
 

Other User Comments


 There are no comments on this submission.
 

Add Your Feedback
Your feedback will be posted below and an email sent to the author. Please remember that the author was kind enough to share this with you, so any criticisms must be stated politely, or they will be deleted. (For feedback not related to this particular code, please click here instead.)
 

To post feedback, first please login.