Physics Behavior Question - GameCreators Forum

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SageTech

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Joined: 3rd Dec 2004

Location: Orlando, Florida

Posted: 8th Jun 2012 13:54 Edited at: 8th Jun 2012 13:56

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I'm trying to create a building structure made out of Metal Beams. Below is the Code which sets this up:

rem
rem AGK Application
rem

rem Portrait App
SetDisplayAspect(1.33)

//set sync rate
SetSyncRate( 1, 0 )

//Set Gravity
SetPhysicsGravity(0,8)

//Create Ground
GroundSprite = createsprite(0)
setspritesize(GroundSprite,100,10)
setspriteposition(GroundSprite,0,90)
setspritecolor(GroundSprite,239,228,176,255)
SetSpritePhysicsOn(GroundSprite,1)

//Create Girder Structure
for b = 17 to 77 step 7
    for i = 5 to 14
        GirderTall = createsprite(0)
        setspritecolor(GirderTall,random(1,255),random(1,255),random(1,255),255)
        setspritesize(GirderTall,1,6)
        setspriteposition(GirderTall,i*5,100-b+1)
        SetSpritePhysicsOn(GirderTall,2)
        SetSpritePhysicsRestitution(GirderTall,0)
        SetSpritePhysicsMass(GirderTall,0.2)
        SetSpritePhysicsFriction(GirderTall,1)
    next i

for i = 5 to 13
        GirderWide = createsprite(0)
        setspritecolor(GirderWide,random(1,255),random(1,255),random(1,255),255)
        setspritesize(GirderWide,5,1)
        setspriteposition(GirderWide,i*5+.5,100-b)
        SetSpritePhysicsOn(GirderWide,2)
        SetSpritePhysicsRestitution(GirderWide,0)
        SetSpritePhysicsMass(GirderWide,0.2)
        SetSpritePhysicsFriction(GirderWide,1)
    next i
    sync()
next b

do

//delete girder user selects
    if getpointerpressed()>0
        SelectedGirderDelete = GetSpriteHit(GetPointerX(),GetPointerY())
        if SelectedGirderDelete > 0
            deletesprite(SelectedGirderDelete)
        endif
    endif

// update the screen
    Print("FPS: " + str(ScreenFPS()))
    Print(GetPointerX())
    Print(GetPointerY())
    Sync()

loop

+ Code Snippet

rem
rem AGK Application
rem

rem Portrait App
SetDisplayAspect(1.33)



//set sync rate
SetSyncRate( 1, 0 )

//Set Gravity
SetPhysicsGravity(0,8)

//Create Ground
GroundSprite = createsprite(0)
setspritesize(GroundSprite,100,10)
setspriteposition(GroundSprite,0,90)
setspritecolor(GroundSprite,239,228,176,255)
SetSpritePhysicsOn(GroundSprite,1)

//Create Girder Structure
for b = 17 to 77 step 7
    for i = 5 to 14
        GirderTall = createsprite(0)
        setspritecolor(GirderTall,random(1,255),random(1,255),random(1,255),255)
        setspritesize(GirderTall,1,6)
        setspriteposition(GirderTall,i*5,100-b+1)
        SetSpritePhysicsOn(GirderTall,2)
        SetSpritePhysicsRestitution(GirderTall,0)
        SetSpritePhysicsMass(GirderTall,0.2)
        SetSpritePhysicsFriction(GirderTall,1)
    next i

    for i = 5 to 13
        GirderWide = createsprite(0)
        setspritecolor(GirderWide,random(1,255),random(1,255),random(1,255),255)
        setspritesize(GirderWide,5,1)
        setspriteposition(GirderWide,i*5+.5,100-b)
        SetSpritePhysicsOn(GirderWide,2)
        SetSpritePhysicsRestitution(GirderWide,0)
        SetSpritePhysicsMass(GirderWide,0.2)
        SetSpritePhysicsFriction(GirderWide,1)
    next i
    sync()
next b

do

    //delete girder user selects
    if getpointerpressed()>0
        SelectedGirderDelete = GetSpriteHit(GetPointerX(),GetPointerY())
        if SelectedGirderDelete > 0
            deletesprite(SelectedGirderDelete)
        endif
    endif

    // update the screen
    Print("FPS: " + str(ScreenFPS()))
    Print(GetPointerX())
    Print(GetPointerY())
    Sync()

loop

EDIT: I'm running this in a 1024X768 Resolution

I've set the sync rate to 1 to slow it down so that you can see whats happening more clearly. Basically, before I had enabled physics all the beams were lined up perfectly so that they should be be supported and the building should stay erect. However, from what I can tell the problem is as the physics simulation adds more shapes on top it sort of bounces the beams below, additionally the shapes seem to twitch and not stay where they were originally positioned. Is this just the standard functionality of the physics system or is their some property I can adjust to make the beams act more realistically?

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baxslash

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Bronze Codemaster

17

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Joined: 26th Dec 2006

Location: Duffield

Posted: 8th Jun 2012 15:00

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It might work better if you don't turn physics on until after everything is in place. That will help in two ways; first your structure is more likely to settle quickly if everything is placed correctly; second you can leave physics off to see if your positioning code is correct.

I would add all items to an array as they are created and then turn physics on by looping through the array.

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Ancient Lady

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Joined: 17th Mar 2004

Location: Anchorage, Alaska, USA

Posted: 8th Jun 2012 18:06

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I tried baxslash's suggestion and added some frame rate changes this way:

dim the_sprites[1000] AS integer
i_spr = 0
rem Portrait App
SetDisplayAspect(1.33)

//set sync rate
SetSyncRate( 10, 0 )

//Set Gravity
SetPhysicsGravity(0,8)

//Create Ground
GroundSprite = createsprite(0)
setspritesize(GroundSprite,100,10)
setspriteposition(GroundSprite,0,90)
setspritecolor(GroundSprite,239,228,176,255)
SetSpritePhysicsOn(GroundSprite,1)

//Create Girder Structure
for b = 17 to 77 step 7
    for i = 5 to 14
        GirderTall = createsprite(0)
        setspritecolor(GirderTall,random(1,255),random(1,255),random(1,255),255)
        setspritesize(GirderTall,1,6)
        setspriteposition(GirderTall,i*5,100-b+1)
		  the_sprites[i_spr] = GirderTall
 		  INC i_spr
    next i

for i = 5 to 13
        GirderWide = createsprite(0)
        setspritecolor(GirderWide,random(1,255),random(1,255),random(1,255),255)
        setspritesize(GirderWide,5,1)
        setspriteposition(GirderWide,i*5+.5,100-b)
 		  the_sprites[i_spr] = GirderWide
		  INC i_spr
    next i
    sync()
next b

DEC i_spr
for i=0 to i_spr
    SetSpritePhysicsOn(the_sprites[i],2)
    SetSpritePhysicsRestitution(the_sprites[i],0)
    SetSpritePhysicsMass(the_sprites[i],0.2)
    SetSpritePhysicsFriction(the_sprites[i],1)
next i
sync()
SetSyncRate( 30, 0 )

do

//delete girder user selects
    if getpointerpressed()>0
        SelectedGirderDelete = GetSpriteHit(GetPointerX(),GetPointerY())
        if SelectedGirderDelete > 0
            deletesprite(SelectedGirderDelete)
        endif
    endif

// update the screen
    Print("FPS: " + str(ScreenFPS()))
    Print(GetPointerX())
    Print(GetPointerY())
    Sync()

loop

+ Code Snippet

dim the_sprites[1000] AS integer
i_spr = 0
rem Portrait App
SetDisplayAspect(1.33)

//set sync rate
SetSyncRate( 10, 0 )

//Set Gravity
SetPhysicsGravity(0,8)

//Create Ground
GroundSprite = createsprite(0)
setspritesize(GroundSprite,100,10)
setspriteposition(GroundSprite,0,90)
setspritecolor(GroundSprite,239,228,176,255)
SetSpritePhysicsOn(GroundSprite,1)

//Create Girder Structure
for b = 17 to 77 step 7
    for i = 5 to 14
        GirderTall = createsprite(0)
        setspritecolor(GirderTall,random(1,255),random(1,255),random(1,255),255)
        setspritesize(GirderTall,1,6)
        setspriteposition(GirderTall,i*5,100-b+1)
		  the_sprites[i_spr] = GirderTall
 		  INC i_spr
    next i

    for i = 5 to 13
        GirderWide = createsprite(0)
        setspritecolor(GirderWide,random(1,255),random(1,255),random(1,255),255)
        setspritesize(GirderWide,5,1)
        setspriteposition(GirderWide,i*5+.5,100-b)
 		  the_sprites[i_spr] = GirderWide
		  INC i_spr
    next i
    sync()
next b

DEC i_spr
for i=0 to i_spr
    SetSpritePhysicsOn(the_sprites[i],2)
    SetSpritePhysicsRestitution(the_sprites[i],0)
    SetSpritePhysicsMass(the_sprites[i],0.2)
    SetSpritePhysicsFriction(the_sprites[i],1)
next i
sync()
SetSyncRate( 30, 0 )

do

    //delete girder user selects
    if getpointerpressed()>0
        SelectedGirderDelete = GetSpriteHit(GetPointerX(),GetPointerY())
        if SelectedGirderDelete > 0
            deletesprite(SelectedGirderDelete)
        endif
    endif

    // update the screen
    Print("FPS: " + str(ScreenFPS()))
    Print(GetPointerX())
    Print(GetPointerY())
    Sync()

loop

When I left the frame rate at 1, the building built stabily, but once physics was turned on, it crumbled.

When I changed the frame rate, it worked very nicely. Cool physics demo!

Cheers,
Ancient Lady

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Ancient Lady

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Joined: 17th Mar 2004

Location: Anchorage, Alaska, USA

Posted: 8th Jun 2012 18:09 Edited at: 8th Jun 2012 18:11

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You can actually have quite a bit of fun playing with deleting select girders!

But, then again, I am so easily entertained.

EDIT: This looks like a good start for a kid's game.

Cheers,
Ancient Lady

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polomint

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Joined: 3rd Apr 2012

Location: Lancashire, United Kingdom

Posted: 8th Jun 2012 20:12

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Ooooo, I must have a play,

Blackberry App Development & ZX Spectrum Game Development.

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Ancient Lady

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Years of Service

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Joined: 17th Mar 2004

Location: Anchorage, Alaska, USA

Posted: 8th Jun 2012 21:15

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It's fun. But, as I said, I'm easily entertained (just ask anyone in my family).

Cheers,
Ancient Lady

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SageTech

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Joined: 3rd Dec 2004

Location: Orlando, Florida

Posted: 10th Jun 2012 10:31

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Thanks, it started off as just a tech demo, where I was experimenting with buildings that could be damaged in real time during an action game. But, I found that it was kind of fun to just randomly delete select girders and see how you can effectively implode the tower. I'm working on a game now using this concept, I'll post a wip when I make a little more progress

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Impetus73

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Joined: 28th Aug 2011

Location: Volda, Norway

Posted: 10th Jun 2012 12:55

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Physics are inherently inaccurate, but here is my best shoot! I don't think the percentage system works too good with physics, so I use virtual resolution system, to get pixel perfection.

The sprites are setup at pixel perfection, but as soon as the physics system is activated, some forces messes with that.

// Rewrite to resolution based, by: impetus73

dim the_sprites[1000] AS integer
i_spr = 0
rem Portrait App
SetVirtualResolution(1024,768)

//set sync rate
SetSyncRate( 60, 0 )

//Set Gravity
SetPhysicsGravity(0,100)

//Create Ground
GroundSprite = createsprite(0)
setspritesize(GroundSprite,1024,75)
setspriteposition(GroundSprite,0,693)
setspritecolor(GroundSprite,239,228,176,255)

SetSpritePhysicsOn(GroundSprite,1)

//Create Girder Structure

for x=1 to 10
    for y=1 to 9
        GirderTall=createsprite(0)
        setspritecolor(GirderTall,random(1,200)+55,random(1,200)+55,random(1,200)+55,255)
        setspritesize(GirderTall,10,40)
        setspriteposition(GirderTall,270+(x*44),693-(y*50))
        the_sprites[i_spr] = GirderTall
 		INC i_spr
    next y
next x
for x=1 to 9
    for y=1 to 10
        GirderWide=createsprite(0)
        setspritecolor(GirderWide,random(1,200)+55,random(1,200)+55,random(1,200)+55,255)
        setspritesize(GirderWide,40,10)
        setspriteposition(GirderWide,277+(x*44),733-(y*50))
        the_sprites[i_spr] = GirderWide
 		INC i_spr
    next y
next x

DEC i_spr
while getpointerpressed()=0
    Print("Press screen to activate physics!")
    sync()
endwhile

for i=0 to i_spr
    SetSpritePhysicsOn(the_sprites[i],2)
    SetSpritePhysicsRestitution(the_sprites[i],0)
    SetSpritePhysicsMass(the_sprites[i],10)
    SetSpritePhysicsFriction(the_sprites[i],0.1)
next i

do
    //delete girder user selects
    if getpointerpressed()>0
        SelectedGirderDelete = GetSpriteHit(GetPointerX(),GetPointerY())
        if SelectedGirderDelete > 0
            deletesprite(SelectedGirderDelete)
        endif
    endif

// update the screen
    Print("FPS: " + str(ScreenFPS()))
    Print(GetPointerX())
    Print(GetPointerY())
    Sync()
loop

+ Code Snippet


// Rewrite to resolution based, by: impetus73

dim the_sprites[1000] AS integer
i_spr = 0
rem Portrait App
SetVirtualResolution(1024,768)

//set sync rate
SetSyncRate( 60, 0 )

//Set Gravity
SetPhysicsGravity(0,100)

//Create Ground
GroundSprite = createsprite(0)
setspritesize(GroundSprite,1024,75)
setspriteposition(GroundSprite,0,693)
setspritecolor(GroundSprite,239,228,176,255)

SetSpritePhysicsOn(GroundSprite,1)

//Create Girder Structure

for x=1 to 10
    for y=1 to 9
        GirderTall=createsprite(0)
        setspritecolor(GirderTall,random(1,200)+55,random(1,200)+55,random(1,200)+55,255)
        setspritesize(GirderTall,10,40)
        setspriteposition(GirderTall,270+(x*44),693-(y*50))
        the_sprites[i_spr] = GirderTall
 		INC i_spr
    next y
next x
for x=1 to 9
    for y=1 to 10
        GirderWide=createsprite(0)
        setspritecolor(GirderWide,random(1,200)+55,random(1,200)+55,random(1,200)+55,255)
        setspritesize(GirderWide,40,10)
        setspriteposition(GirderWide,277+(x*44),733-(y*50))
        the_sprites[i_spr] = GirderWide
 		INC i_spr
    next y
next x

DEC i_spr
while getpointerpressed()=0
    Print("Press screen to activate physics!")
    sync()
endwhile

for i=0 to i_spr
    SetSpritePhysicsOn(the_sprites[i],2)
    SetSpritePhysicsRestitution(the_sprites[i],0)
    SetSpritePhysicsMass(the_sprites[i],10)
    SetSpritePhysicsFriction(the_sprites[i],0.1)
next i

do
    //delete girder user selects
    if getpointerpressed()>0
        SelectedGirderDelete = GetSpriteHit(GetPointerX(),GetPointerY())
        if SelectedGirderDelete > 0
            deletesprite(SelectedGirderDelete)
        endif
    endif

    // update the screen
    Print("FPS: " + str(ScreenFPS()))
    Print(GetPointerX())
    Print(GetPointerY())
    Sync()
loop

Maybe if one carefully activate physics for each sprite in the right order from the bottom and up, then call Sync() between sets of sprites, it would end up perfectly balanced?

----------------
AGK user - novice
Did Amiga / AMOS programming in the 90's, just started programming again with AGK.

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