Here's a little physics demo I wrote to kill some time at work... Enjoy.
Open the attached JAR file and/or download the source code.
PhysiX.b4j
Vector.bas
Open the attached JAR file and/or download the source code.
PhysiX.b4j
B4X:
#Region Project Attributes
#MainFormWidth: 600
#MainFormHeight: 400
#End Region
Sub Process_Globals
'Custom Types
Type PhysicalObject2D(posX As Double, posY As Double, sizeX As Double, sizeY As Double, Velocity As Vector, Gravity As Vector)
Type Line2D(aX As Double, aY As Double, bX As Double, bY As Double, Active As Boolean)
Type PerformanceMeasurement(Interval As Double, TimeStamp As Long)
'MainForm
Private fx As JFX
Private MainForm As Form
Dim cvs As Canvas
'Main Cycle
Dim DeltaTime As PerformanceMeasurement
Dim MainCycle As Timer
'Physical Elements
Dim LittleSquare As PhysicalObject2D
Dim Platform As PhysicalObject2D
Dim World As PhysicalObject2D
'Temporary Variables
Dim tempVelocity As Vector
Dim tempGravity As Vector
'Constants
Dim EarthMass = 5.972 * Power(10, 24) As Double
'User Input
Dim LaunchVisual As Line2D
Dim UserInput As Pane
End Sub
Sub AppStart (Form1 As Form, Args() As String)
'MainForm Settings
MainForm = Form1
MainForm.Resizable = False
MainForm.Title = "LittleSquare Physics Demo  Bruno Silva 2015"
MainForm.SetFormStyle("UNIFIED")
MainForm.Show
'Canvas
cvs.Initialize("cvs")
MainForm.RootPane.AddNode(cvs, 0, 0, MainForm.Width, MainForm.Height)
'User Input
UserInput.Initialize("UserInput")
MainForm.RootPane.AddNode(UserInput, 0, 0, MainForm.Width, MainForm.Height)
'World Gravity
tempGravity.setAngleAndMagnitudeD(90, 1600)
World.Gravity = tempGravity
'Player
LittleSquare.sizeX = 15
LittleSquare.sizeY = 15
LittleSquare.posX = Rnd(0, cvs.Width  LittleSquare.sizeX)
LittleSquare.posY = 0
'Player Velocity
tempVelocity.setAngleAndMagnitudeD(Rnd(0,360), 300)
LittleSquare.Velocity = tempVelocity
'Stage
Platform.sizeX = cvs.Width
Platform.sizeY = 100
Platform.posX = 0
Platform.posY = cvs.Height  Platform.sizeY
'Main Cycle
DeltaTime.Interval = (1 / 60)
MainCycle.Initialize("MainCycle", 16) 'DeltaTime.Interval * 1000)
MainCycle.Enabled = True
End Sub
Sub MainCycle_Tick
'Calculate DeltaTime Interval
If Not(DeltaTime.TimeStamp = 0) Then DeltaTime.Interval = (Max(1, DateTime.Now  DeltaTime.TimeStamp) / 1000)
DeltaTime.TimeStamp = DateTime.Now
'Clear Screen
cvs.ClearRect(0, 0, cvs.Width, cvs.Height)
'Apply Gravity Physics
tempVelocity.dirY = LittleSquare.Velocity.dirY + (World.Gravity.dirY * DeltaTime.Interval)
LittleSquare.Velocity = tempVelocity
'Collision Detection: Platform
If LittleSquare.posY + LittleSquare.sizeY >= Platform.posY Then
If LittleSquare.posY + LittleSquare.sizeY > Platform.posY And LittleSquare.Velocity.AngleD <= 180 Then
tempVelocity.dirY = PostCollisionVelocity(LittleSquare.Velocity.dirY, 0, 10, EarthMass, 0.6)
LittleSquare.Velocity = tempVelocity
End If
If Abs(LittleSquare.Velocity.dirY) < Abs(0.05 * World.Gravity.dirY) Then
tempVelocity.dirY = 0
LittleSquare.Velocity = tempVelocity
End If
LittleSquare.posY = Platform.posY  LittleSquare.sizeY
End If
'Collision Detection: Top
If LittleSquare.posY < 0 Then
LittleSquare.posY = 0
tempVelocity.dirY = PostCollisionVelocity(LittleSquare.Velocity.dirY, 0, 10, EarthMass, 0.6)
LittleSquare.Velocity = tempVelocity
End If
'Collision Detection: Walls
If LittleSquare.posX + LittleSquare.sizeX > cvs.Width Then
LittleSquare.posX = cvs.Width  LittleSquare.sizeX
tempVelocity.dirX = PostCollisionVelocity(LittleSquare.Velocity.dirX, 0, 10, EarthMass, 0.6)
LittleSquare.Velocity = tempVelocity
Else If LittleSquare.posX < 0 Then
LittleSquare.posX = 0
tempVelocity.dirX = PostCollisionVelocity(LittleSquare.Velocity.dirX, 0, 10, EarthMass, 0.6)
LittleSquare.Velocity = tempVelocity
End If
'Friction
If LittleSquare.posY + LittleSquare.sizeY >= Platform.posY Then
tempVelocity.dirX = LittleSquare.Velocity.dirX * 0.8
LittleSquare.Velocity = tempVelocity
End If
'Backup Coords
Dim oX = LittleSquare.posX As Double
Dim oY = LittleSquare.posY As Double
'Update Position
LittleSquare.posX = LittleSquare.posX + (LittleSquare.Velocity.dirX * DeltaTime.Interval)
LittleSquare.posY = LittleSquare.posY + (LittleSquare.Velocity.dirY * DeltaTime.Interval)
'Calculate the Velocity Angle
tempVelocity.AngleD = CalcAngleD(oX, oY, LittleSquare.posX, LittleSquare.posY)
LittleSquare.Velocity = tempVelocity
'Render on Screen
DrawShape(LittleSquare, fx.Colors.Blue)
DrawShape(Platform, fx.Colors.Green)
If LaunchVisual.Active Then
LaunchVisual.aX = LittleSquare.posX + (LittleSquare.sizeX / 2)
LaunchVisual.aY = LittleSquare.posY + (LittleSquare.sizeY / 2)
DrawLine(LaunchVisual, fx.Colors.Red, 2)
End If
'Debug
'Log(DeltaTime.Interval)
End Sub
'Given the Conservation of Momentum formula (m1*u1)+(m2*u2) = (m1*v1)+(m2*v2),
'we're able to calculate an object's post collision velocity.
'
'u1: ObjectA precollision velocity, u2: ObjectB precollision velocity, m1: ObjectA mass in kg, m2: ObjectB mass in kg.
'CoR: Coefficient of Restitution, a value between 0.00(0) and 1.00(0) where 1 represents a perfectly elastic collision.
Sub PostCollisionVelocity(u1 As Double, u2 As Double, m1 As Double, m2 As Double, CoR As Double) As Double
Dim v1 = ((u1 * (m1  m2)) + (2 * m2 * u2)) / (m1 + m2) As Double
Return v1 * CoR
End Sub
Sub Userinput_MousePressed (EventData As MouseEvent)
Dim dist, aX, aY, bX, bY As Double
aX = (LittleSquare.posX + LittleSquare.sizeX / 2)
aY = (LittleSquare.posY + LittleSquare.sizeY / 2)
bX = (EventData.X)
bY = (EventData.Y)
dist = Sqrt(Power((bXaX),2) + Power((bYaY),2))
If dist <= LittleSquare.sizeX Then
LaunchVisual.aX = aX
LaunchVisual.aY = aY
LaunchVisual.bX = aX
LaunchVisual.bY = aY
LaunchVisual.Active = True
End If
End Sub
Sub Userinput_MouseDragged (EventData As MouseEvent)
Dim aX, aY, bX, bY As Double
aX = (LittleSquare.posX + LittleSquare.sizeX / 2)
aY = (LittleSquare.posY + LittleSquare.sizeY / 2)
bX = (EventData.X)
bY = (EventData.Y)
If LaunchVisual.Active Then
LaunchVisual.aX = aX
LaunchVisual.aY = aY
LaunchVisual.bX = bX
LaunchVisual.bY = bY
End If
End Sub
Sub Userinput_MouseReleased (EventData As MouseEvent)
Dim angle, dist, aX, aY, bX, bY As Double
aX = (LittleSquare.posX + LittleSquare.sizeX / 2)
aY = (LittleSquare.posY + LittleSquare.sizeY / 2)
bX = (EventData.X)
bY = (EventData.Y)
angle = CalcAngleD(aX, aY, bX, bY)
dist = Sqrt(Power((bXaX),2) + Power((bYaY),2))
If LaunchVisual.active Then
LaunchVisual.bX = bX
LaunchVisual.bY = bY
Dim tempVelocity As Vector
tempVelocity.setAngleAndMagnitudeD(angle, dist * 5)
LittleSquare.Velocity = tempVelocity
End If
LaunchVisual.Active = False
LaunchVisual.aX = 0
LaunchVisual.aY = 0
LaunchVisual.bX = 0
LaunchVisual.bY = 0
End Sub
Public Sub CalcAngleD(aX As Double, aY As Double, bX As Double, bY As Double) As Double
Dim dirX = bX  aX As Double
Dim dirY = bY  aY As Double
Return ATan2D(dirY, dirX)
End Sub
Sub DrawShape(input As PhysicalObject2D, color As Paint)
cvs.DrawRect(input.posX, input.posY, input.sizeX, input.sizeY, color, True, 0)
End Sub
Sub DrawLine(line As Line2D, color As Paint, thickness As Int)
cvs.DrawLine(line.aX, line.aY, line.bX, line.bY, color, thickness)
End Sub
B4X:
'Class module
Private Sub Class_Globals
Private fx As JFX
Dim Description As String
Dim Units As String
Dim Size As Double
Dim AngleD As Double
Dim AngleR As Double
Dim dirX As Double
Dim dirY As Double
End Sub
'Sets this vector's description and units
Public Sub setDescription(Vector_Description As String, Vector_Units As String)
Description = Vector_Description
Units = Vector_Units
End Sub
'Sets this vector's directional components, magnitude and angle from an imaginary line between two points in space, given their X, Y coordinates.
Public Sub setVectorFromLine(aX As Double, aY As Double, bX As Double, bY As Double)
dirX = bX  aX
dirY = bY  aY
AngleD = ATan2D(dirY, dirX)
AngleR = ATan2 (dirY, dirX)
Size = Sqrt(Power(dirX, 2) + Power(dirY, 2))
End Sub
'Sets this vector's directional components based on the given size and angle in degrees.
Public Sub setAngleAndMagnitudeD(Degrees As Double, Magnitude As Double)
AngleD = Degrees
AngleR = Degrees * cPI / 180
Size = Magnitude
dirX = CosD(Degrees) * Magnitude
dirY = SinD(Degrees) * Magnitude
End Sub
'Sets this vector's directional components based on the given size and angle in radians.
Public Sub setAngleAndMagnitudeR(Magnitude As Double, Radians As Double)
AngleD = Radians * 180 / cPI
AngleR = Radians
Size = Magnitude
dirX = Cos(Radians) * Magnitude
dirY = Sin(Radians) * Magnitude
End Sub
'Updates the vector's directional components, magnitude and angle in radians based on the given angle in degrees.
Public Sub setAngleD(Degrees As Double)
AngleD = Degrees
AngleR = Degrees * cPI / 180
dirX = CosD(Degrees) * Size
dirY = SinD(Degrees) * Size
End Sub
'Updates the vector's directional components, magnitude and angle in degrees based on the given angle in radians.
Public Sub setAngleR(Radians As Double)
AngleD = Radians * 180 / cPI
AngleR = Radians
dirX = Cos(Radians) * Size
dirY = Sin(Radians) * Size
End Sub
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