Frictionless space physics - GameCreators Forum

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Mcine

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Posted: 17th Jan 2016 13:23

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Hey,

How can I do frictionless physics for my spacegame ?
I have zeroed the gravity and sprite frictions.
I have 2 sprites joined with distancejoint and other sprite is static.
When I give the dynamic sprite an impulse (upwards), it will rotate around the static one, but the movement keeps getting slower.
How can I remove all frictions, so that the velocity is constant.

- McIne

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Ancient Lady

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Location: Anchorage, Alaska, USA

Posted: 31st Jan 2016 22:24

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Look at the SetSpritePhysicsRestitution and SetSpritePhysicsDamping commands in addition to the SetSpritePhysicsFriction that I suspect you are using.

The first sets the bounciness and the second is the one that will cause something to slow down.

Cheers,
Ancient Lady

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Mcine

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Posted: 1st Feb 2016 13:25

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Thanks for the answer. I need to check all those through.
I think I have damping and friction set to 0, but have not set restitution since I thought it would not matter.

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Mcine

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Posted: 1st Feb 2016 19:05

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That did not help..

I create the sprites like this (one static and one dynamic)
SetSpriteSize(p1,50,50)
SetSpritePositionByOffset(p1,300,300)
setspritephysicson (p1, 2)
SetSpriteShapeCircle(p1,0,0,25)
SetSpritePhysicsFriction(p1,0)
SetSpritePhysicsDamping(p1,0)
SetSpritePhysicsMass(p1,1)
SetSpritePhysicsRestitution (p1,1)

And I create a distance joint between them and put other in motion and it slows down.

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CJB

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Posted: 3rd Feb 2016 11:33

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You could cheat with a Joint Motor:

// Project: spacefriction 
// Created: 2016-02-03
// set window properties
SetWindowTitle( "spacefriction" )
SetWindowSize( 1024, 768, 0 )

SetPhysicsScale(0.4)

p1 = createsprite(0)
setspritecolor(p1,255,255,255,255)
SetSpriteSize(p1,50,50)
SetSpritePositionByOffset(p1,500,500)
setspritephysicson (p1, 2)
SetSpriteShapeCircle(p1,0,0,25)
SetSpritePhysicsFriction(p1,0)
SetSpritePhysicsDamping(p1,0)
SetSpritePhysicsMass(p1,10)
SetSpritePhysicsRestitution(p1,0)
SetSpritePhysicsAngularDamping(p1,0)

p2 = createsprite(0)
setspritecolor(p2,255,255,255,255)
SetSpriteSize(p2,50,50)
SetSpritePositionByOffset(p2,300,300)
setspritephysicson (p2, 1)
SetSpriteShapeCircle(p2,0,0,25)
SetSpritePhysicsFriction(p2,0)
SetSpritePhysicsDamping(p2,0)
SetSpritePhysicsMass(p2,10)
SetSpritePhysicsRestitution(p2,0)
SetSpritePhysicsAngularDamping(p2,0)

CreateRevoluteJoint(1,p1,p2,GetSpriteXByOffset(p2),GetSpriteYByOffset(p2),0)

SetPhysicsGravity(0,0)

SetJointMotorOn( 1, -10, 10000 )

SetViewZoom(1.1) // just using this to quickly turn off physics walls.

// set display properties
SetVirtualResolution( 1024, 768 )
SetOrientationAllowed( 1, 1, 1, 1 )

do
    Print( ScreenFPS() )
    StepPhysics(0.16)
    Sync()
loop

+ Code Snippet

// Project: spacefriction 
// Created: 2016-02-03
// set window properties
SetWindowTitle( "spacefriction" )
SetWindowSize( 1024, 768, 0 )

SetPhysicsScale(0.4)

p1 = createsprite(0)
setspritecolor(p1,255,255,255,255)
SetSpriteSize(p1,50,50)
SetSpritePositionByOffset(p1,500,500)
setspritephysicson (p1, 2)
SetSpriteShapeCircle(p1,0,0,25)
SetSpritePhysicsFriction(p1,0)
SetSpritePhysicsDamping(p1,0)
SetSpritePhysicsMass(p1,10)
SetSpritePhysicsRestitution(p1,0)
SetSpritePhysicsAngularDamping(p1,0)

p2 = createsprite(0)
setspritecolor(p2,255,255,255,255)
SetSpriteSize(p2,50,50)
SetSpritePositionByOffset(p2,300,300)
setspritephysicson (p2, 1)
SetSpriteShapeCircle(p2,0,0,25)
SetSpritePhysicsFriction(p2,0)
SetSpritePhysicsDamping(p2,0)
SetSpritePhysicsMass(p2,10)
SetSpritePhysicsRestitution(p2,0)
SetSpritePhysicsAngularDamping(p2,0)

CreateRevoluteJoint(1,p1,p2,GetSpriteXByOffset(p2),GetSpriteYByOffset(p2),0)

SetPhysicsGravity(0,0)

SetJointMotorOn( 1, -10, 10000 ) 

SetViewZoom(1.1) // just using this to quickly turn off physics walls.

// set display properties
SetVirtualResolution( 1024, 768 )
SetOrientationAllowed( 1, 1, 1, 1 )

do
    Print( ScreenFPS() )
    StepPhysics(0.16)
    Sync()
loop

V2 T1 (Mostly)
Phone Tap!
Uzmadesign

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Ancient Lady

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Joined: 17th Mar 2004

Location: Anchorage, Alaska, USA

Posted: 4th Feb 2016 02:43

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And it might be possible that the 'SetSpritePhysicsMass(p1,1)' command is resetting the Friction and Damping. Try moving it to just after the 'SetSpriteSize(p1,50,50)' call.

Cheers,
Ancient Lady

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