Getting a very bad framerate in VB.net physics simulation. Any suggestions? - vb.net

Question

I am making a gravity/solar system simulation and when the simulation runs I am only getting about 5 fps. Here is the relevant part of my code:
Private Sub Form1_Paint(sender As Object, e As PaintEventArgs) Handles picSpace.Paint
earth.displayX = Math.Round(earth.positionX)
earth.displayY = Math.Round(earth.positionY)
e.Graphics.FillEllipse(Brushes.Blue, earth.displayX - 5, earth.displayY - 5, 10, 10)
e.Graphics.FillEllipse(Brushes.Yellow, sunX - 10, sunY - 10, 20, 20)
distance()
position()
End Sub
Sub distance()
dX = sunX - earth.positionX
dY = sunY - earth.positionY
If (earth.positionX >= sunX) And (earth.positionY <= sunY) Then
dX *= -1
Else
If (earth.positionX >= sunX) And (earth.positionY >= sunY) Then
dX *= -1
dY *= -1
Else
If (earth.positionX <= sunX) And (earth.positionY >= sunY) Then
dY *= -1
Else
If (earth.positionX <= sunX) And (earth.positionY <= sunY) Then
'do nothing
End If
End If
End If
End If
d = Math.Sqrt((((dY) * 1000000) ^ 2) + (((dX) * 1000000) ^ 2))
d = d * 1000
End Sub
Sub position()
If first = False Then
earth.positionX += ((((earth.oldVelocityX + earth.velocityX) / 2) * simulationSpeed) / 1000000000)
earth.positionY += ((((earth.oldVelocityY + earth.velocityY) / 2) * simulationSpeed) / 1000000000)
orbit(0, counter) = earth.positionX
orbit(1, counter) = earth.positionY
counter += 1
ReDim Preserve orbit(1, counter)
lblPositionX.Text = "X: " & Math.Truncate(earth.positionX)
lblPositionY.Text = "Y: " & Math.Truncate(earth.positionY)
End If
F = (earth.mass * sunMass * G) / (d ^ 2)
theta = Math.Atan(dX / dY)
If (earth.positionX >= sunX) And (earth.positionY <= sunY) Then
earth.forceX = F * Math.Sin(theta) * -1
earth.forceY = F * Math.Cos(theta)
Else
If (earth.positionX >= sunX) And (earth.positionY >= sunY) Then
earth.forceX = F * Math.Sin(theta) * -1
earth.forceY = F * Math.Cos(theta) * -1
Else
If (earth.positionX <= sunX) And (earth.positionY >= sunY) Then
earth.forceX = F * Math.Sin(theta)
earth.forceY = F * Math.Cos(theta) * -1
Else
If (earth.positionX <= sunX) And (earth.positionY <= sunY) Then
earth.forceX = F * Math.Sin(theta)
earth.forceY = F * Math.Cos(theta)
End If
End If
End If
End If
a = F / earth.mass
earth.accelerationX = earth.forceX / earth.mass
earth.accelerationY = earth.forceY / earth.mass
earth.oldVelocityX = earth.velocityX
earth.oldVelocityY = earth.velocityY
earth.velocityX = earth.oldVelocityX + (earth.accelerationX * simulationSpeed)
earth.velocityY = earth.oldVelocityY + (earth.accelerationY * simulationSpeed)
first = False
Me.Refresh()
End Sub
Originally I had a large portion of the code in a do...loop and the framerate was fine, but I could not interact with any controls while the loop was running. Doing it as shown above lets me interact with controls but the framerate is very choppy. Any help would be greatly appreciated.

Answer 1

Calling Refresh from within Paint is very odd. One possible performance issue is that this forces the entire form to repaint including the background. I would suggest 2 things:
Create a timer object, and perform the calculation and updates from within Timer_Tick event.
Then remove the Me.Refresh command from sub position(), so that position() and distance() just do calculations. Add a call to Me.Invalidate() at the beginning and end of the Timer_Tick passing it the rectangle containing the location of the earth. This will force only the old and new locations to be repainted and won't repaint a lot of unchanged background. Your Paint method is then likely to just be the 2 FillEllipse lines.