Unable to wrap my head around prismatic joints

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Tikkiwich

19

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Joined: 30th Jan 2005

Location: Barnsley, South Yorkshire

Posted: 7th Jul 2009 00:40

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Hi, I have been trying to understand how to use prismatic joints and have failed miserably. In my test code below, the cubes seem to first jump to a central point then are attached to an axis along Z (Away from the camera). I assume that I'm doing something wrong with the "axisX#, axisY#, axisZ#" part of the PHY MAKE PRISMATIC JOINT command.
Does anyone know how to use this command and are willing to give an example or could point me in the direction of some tutorials? The tutorial that came with DarkPhysics (Dark Physics\Tutorials\Prismatic Joints) doesn't seem to build the joint and when I add a build command it has the same behaviour as my code.

#Constant RunSpeed = 40 `This value alters the amount the program 'sleeps' when Ctrl is pressed.

Phy Start
Phy Set Ground Plane 0

AutoCam Off
Position Camera 0, 0, 0, -20

Make Object Box 1, 20, 10, 20
Position Object 1, 0, -10, 0
Phy Make Rigid Body Static Box 1

Make Object Cube 2, 5
Color Object 2, RGB( 255,0,0 )
Position Object 2, 0, -2.5, 0
Phy Make Rigid Body Dynamic Box 2

Make Object Cube 3, 5
Color Object 3, RGB( 0, 255, 0 )
Position Object 3, 0, 10, 0
Phy Make Rigid Body Dynamic Box 3

Phy Make Prismatic Joint 1, 2, 3, 0, 0, 0, Object Position X( 3 ), Object Position Y( 3 ), Object Position Z( 3 )
Phy Build Prismatic Joint 1

Latch = 0

While Not EscapeKey()
    Text 1,1, "Press SHIFT to step, hold CONTROL to run."
    If ShiftKey() 
         If Latch = 0
              Phy Update
              Latch = 1
         EndIf
    Else
         Latch = 0
    EndIf
    If ControlKey()
        Phy Update
        Sleep RunSpeed
    EndIf
    Point Camera 0, Object Position X( 2 ), Object Position Y( 2 ), Object Position Z( 2 )
EndWhile

Phy End

+ Code Snippet

#Constant RunSpeed = 40 `This value alters the amount the program 'sleeps' when Ctrl is pressed.

Phy Start
Phy Set Ground Plane 0

AutoCam Off
Position Camera 0, 0, 0, -20

Make Object Box 1, 20, 10, 20
Position Object 1, 0, -10, 0
Phy Make Rigid Body Static Box 1

Make Object Cube 2, 5
Color Object 2, RGB( 255,0,0 )
Position Object 2, 0, -2.5, 0
Phy Make Rigid Body Dynamic Box 2

Make Object Cube 3, 5
Color Object 3, RGB( 0, 255, 0 )
Position Object 3, 0, 10, 0
Phy Make Rigid Body Dynamic Box 3

Phy Make Prismatic Joint 1, 2, 3, 0, 0, 0, Object Position X( 3 ), Object Position Y( 3 ), Object Position Z( 3 )
Phy Build Prismatic Joint 1

Latch = 0

While Not EscapeKey()
    Text 1,1, "Press SHIFT to step, hold CONTROL to run."
    If ShiftKey() 
         If Latch = 0
              Phy Update
              Latch = 1
         EndIf
    Else
         Latch = 0
    EndIf
    If ControlKey()
        Phy Update
        Sleep RunSpeed
    EndIf
    Point Camera 0, Object Position X( 2 ), Object Position Y( 2 ), Object Position Z( 2 )
EndWhile

Phy End

Thanks in advance!

Foil wrapped for crunchiness

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HowDo

21

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Joined: 28th Nov 2002

Location: United Kingdom

Posted: 7th Jul 2009 10:47 Edited at: 7th Jul 2009 10:49

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see if this help you to get were you want.

+ Code Snippet

Rem Project: prismaticjoint
Rem Created: 25/02/2009 16:41:16

Rem ***** Main Source File *****

sync on
sync rate 60

autocam off
position camera 0,6,-40
point camera 0,0,0
phy enable debug
phy start




    make object box 1, 10,10,10

            position object 1, -10, 0, 0

            phy make rigid body dynamic box 1



            make object box 2, 9,9,9

            position object 2, 10, 0, 0

            phy make rigid body dynamic box 2



            phy make prismatic joint 1, 1, 2

            phy set prismatic joint global axis 1, 0, 1, 0, 0

            phy set prismatic joint global axis 1, 1, 1, 0, 0

            phy build prismatic joint 1

make object box 10,100,1,100
position object 10,0,-5,0
phy make rigid body static box 10

do
`phy set rigid body position 1,0,5,0
PHY SET RIGID BODY ROTATION 1,0,0, wrapvalue(object angle z(1)+1)

phy update
sync
loop

edit
full length command does not seem to work so you have to do it bits.

Dark Physics makes any hot drink go cold.

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HowDo

21

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Joined: 28th Nov 2002

Location: United Kingdom

Posted: 7th Jul 2009 11:03

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this seem to make do something.

#Constant RunSpeed = 40 `This value alters the amount the program 'sleeps' when Ctrl is pressed.

Phy Start
Phy Set Ground Plane 0
enable_First_object=0
enable_decond_object=1
AutoCam Off
Position Camera 0, 0, 0, -20

Make Object Box 1, 20, 10, 20
Position Object 1, 0, -10, 0
Phy Make Rigid Body Static Box 1

Make Object Cube 2, 5
Color Object 2, RGB( 255,0,0 )
Position Object 2, 0, -2.5, 0
Phy Make Rigid Body Dynamic Box 2

Make Object Cube 3, 5
Color Object 3, RGB( 0, 255, 0 )
Position Object 3, 0, 10, 0
Phy Make Rigid Body Dynamic Box 3

Phy Make Prismatic Joint 1, 2, 3
phy set prismatic joint global axis 1, enable_First_object, Object Position X( 3 ), Object Position Y( 3 ), Object Position Z( 3 )
phy set prismatic joint global axis 1, enable_decond_object, Object Position x( 2 ), Object Position y( 2 ), Object Position z( 2 )

Phy Build Prismatic Joint 1

Latch = 0

While Not EscapeKey()
    Text 1,1, "Press SHIFT to step, hold CONTROL to run."
    If ShiftKey()
         If Latch = 0
              Phy Update
              Latch = 1
         EndIf
    Else
         Latch = 0
    EndIf
    If ControlKey()
        Phy Update
        Sleep RunSpeed
    EndIf
    Point Camera 0, Object Position X( 2 ), Object Position Y( 2 ), Object Position Z( 2 )
EndWhile

Phy End

+ Code Snippet

#Constant RunSpeed = 40 `This value alters the amount the program 'sleeps' when Ctrl is pressed.

Phy Start
Phy Set Ground Plane 0
enable_First_object=0
enable_decond_object=1
AutoCam Off
Position Camera 0, 0, 0, -20

Make Object Box 1, 20, 10, 20
Position Object 1, 0, -10, 0
Phy Make Rigid Body Static Box 1

Make Object Cube 2, 5
Color Object 2, RGB( 255,0,0 )
Position Object 2, 0, -2.5, 0
Phy Make Rigid Body Dynamic Box 2

Make Object Cube 3, 5
Color Object 3, RGB( 0, 255, 0 )
Position Object 3, 0, 10, 0
Phy Make Rigid Body Dynamic Box 3

Phy Make Prismatic Joint 1, 2, 3
phy set prismatic joint global axis 1, enable_First_object, Object Position X( 3 ), Object Position Y( 3 ), Object Position Z( 3 )
phy set prismatic joint global axis 1, enable_decond_object, Object Position x( 2 ), Object Position y( 2 ), Object Position z( 2 )

Phy Build Prismatic Joint 1

Latch = 0

While Not EscapeKey()
    Text 1,1, "Press SHIFT to step, hold CONTROL to run."
    If ShiftKey()
         If Latch = 0
              Phy Update
              Latch = 1
         EndIf
    Else
         Latch = 0
    EndIf
    If ControlKey()
        Phy Update
        Sleep RunSpeed
    EndIf
    Point Camera 0, Object Position X( 2 ), Object Position Y( 2 ), Object Position Z( 2 )
EndWhile

Phy End

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Tikkiwich

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Joined: 30th Jan 2005

Location: Barnsley, South Yorkshire

Posted: 7th Jul 2009 19:41

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Thanks, HowDo - works perfectly! You have saved me alot of stress

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Dark Physics & Dark A.I. & Dark Dynamix / Unable to wrap my head around prismatic joints