Physics movement issue - GameCreators Forum

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gsdblack

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Joined: 6th Dec 2011

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Posted: 17th Apr 2013 17:27

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I'm working on platformer when the player is constantly moving right and can jump. I tried to do it with out physics but when I "jump' it doesn't really jump. It just places the player -y and isn't really jumping.

+ Code Snippet

agk::SetSpriteX(cynthiaSprite, agk::GetSpriteX ( cynthiaSprite ) + movePlayerx);

        //JUMP--------------------------------------------------------------------------------------------------------------
        if (agk::GetVirtualButtonPressed(6) == 1 )
        {
            if(dbljump)
            {
                agk::SetSpriteY(cynthiaSprite, agk::GetSpriteY(cynthiaSprite) -17);
                dbljump = false;
            }
            
            if(!inair)
            {
 agk::SetSpriteY(cynthiaSprite, agk::GetSpriteY(cynthiaSprite) -25)  ;
 dbljump = true;
            }
            
        }

I tried movement with velocity and impulse but the player wont jump.

+ Code Snippet

//move right
agk::SetSpritePhysicsVelocity(cynthiaSprite, 50, 0 );

//jump
agk::SetSpritePhysicsImpulse(cynthiaSprite, agk::GetSpriteX(cynthiaSprite), agk::GetSpriteY(cynthiaSprite) + 50, 0, -100);

Then I tried force and impulse but it seems the player only move in the air. I guessing it is because of friction but I don't know how to solve that.

+ Code Snippet

//move right
agk::SetSpritePhysicsForce(cynthiaSprite, agk::GetSpriteX(cynthiaSprite) + (agk::GetSpriteHeight(cynthiaSprite) /2),  0, 2000, 0 );

//
agk::SetSpritePhysicsImpulse(cynthiaSprite, agk::GetSpriteX(cynthiaSprite), agk::GetSpriteY(cynthiaSprite) + 50, 0, -100);

What am I doing wrong?

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Markus

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Posted: 17th Apr 2013 17:35 Edited at: 17th Apr 2013 17:39

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use physics movement only with force or impulse.
the best start of force is getspritexbyoffset() & getspriteybyoffset() , this is the standard middle of your sprite.

you forget to set the y pos. parameter.

agk::SetSpritePhysicsForce(cynthiaSprite, agk::getspritexbyoffset(cynthiaSprite), agk::getspriteybyoffset(cynthiaSprite), 2000, 0 );

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lilpissywilly

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Posted: 17th Apr 2013 18:11 Edited at: 17th Apr 2013 18:39

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Like Markus said you should use GetSpriteX&YbyOffset.

But also in your jump code, try this:

+ Code Snippet

agk::SetSpritePhysicsImpulse(cynthiaSprite, agk::GetSpriteXbyOffset(cynthiaSprite), agk::GetSpriteYbyOffset(cynthiaSprite), 0, -100);

If this does nothing, the force is too low for your object, so try -500 or something instead on the Y force.

Edit:
If you want your jump to behave the same no matter what other forces your object is subjected to, you can use setSpritePhysicsVelocity.

+ Code Snippet

agk::SetSpritePhysicsVelocity(cynthiaSprite, agk::getSpritePhysicsVelocityX(cynthiaSprite), -100)

My hovercraft is full of eels

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bitJericho

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Location: United States

Posted: 18th Apr 2013 04:47

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What I did to get very reasonable values was choose a scale for size and mass. I chose 1 unit is a meter and kg for mass. Then I made a reasonable sized and weighted sprite and let it drop. I then tweaked my friction value until terminal velocity was right. This will also confirm your gravity is right. Anyway, once your object is moving in the world correctly you can start tweaking impulses knowing you're using reasonable numbers. When tweaking impulses, you may also want to keep track of the sprite speed so you know how fast they are moving and are moving appropriately fast for your game.

Visit my blog http://www.canales.me.

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gsdblack

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Posted: 21st Apr 2013 21:10

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I've tried what you guys posted but it still doesn't look/feel right. How can I make the player jump without physics.

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Marl

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Location: Bradford, UK

Posted: 24th Apr 2013 20:42

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You can simulate physics. I've had a lot of success with a "stripped down" physics model for similar ideas that don't need the full physics effects.

Each object is assigned properties for position,speed and acceleration for the axes you want to work with. Then each loop - or at an interval which suits your game - you add the acceleration to the speed, then add the speed to the position.

Each property has a maximum and minimum value to stop it getting silly, but the rest is pretty much self working.

I used it for a space type movement system ( parameters for x, y and angle ) and it provided a very realistic feeling of inertia.

I'll see if I can dig out the code.

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gsdblack

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Posted: 8th May 2013 06:05

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Sounds complicated....

. Could you dig it up for me?

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Marl

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Posted: 8th May 2013 09:33 Edited at: 8th May 2013 09:34

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Here's the setup for the objects

+ Code Snippet

#constant V2_MAX_OBJECTS	100
#constant V2_ANGLE_RIGHT	0.0
#constant V2_ANGLE_UP		90.0
#constant V2_ANGLE_LEFT		180.0
#constant V2_ANGLE_DOWN		270.0

type V2CoordTypeF
	x#
	y#
	a#
	r#
endtype

type V2ControlTypeF
	maxObjects
	topObject
endtype

function Vect2_Init()
	global Vect2Init = 1
	global V2Control as V2ControlTypeF
	V2Control.maxObjects = V2_MAX_OBJECTS
	V2Control.topObject = 0
	dim V2Object[ V2_MAX_OBJECTS ] as V2ObjectTypeF
	thisCoord as V2CoordTypeF
	thisCoord = Vect2_NewCoordF()
	for thisObject = 0 to V2_MAX_OBJECTS
		V2Object[thisObject].isLive = 0
		V2Object[thisObject].isMoving = 0
		V2Object[thisObject].pos = thisCoord
		V2Object[thisObject].speed = thisCoord
		V2Object[thisObject].force = thisCoord
		V2Object[thisObject].debugSpriteS = 0
		V2Object[thisObject].debugSpriteF = 0
	next thisObject
endfunction

function Vect2_NewCoordF()
	thisCoordF as V2CoordTypeF
	thisCoordF.x# = 0.0
	thisCoordF.y# = 0.0
	thisCoordF.a# = 0.0
	thisCoordF.r# = 0.0
endfunction thisCoordF

And here's the loop code;

function Vect2_Update( thisTime# )
	// Updates Vector2 Objects based on time
	thisZoom# = 1.0 / getViewZoom()
	thisHeight# = thisZoom# * 2.0
	for thisObject = 0 to V2Control.topObject
		if V2Object[thisObject].isLive and V2Object[thisObject].isMoving
			// Apply Force
			thisIsMoving = 0
			thisFX# = V2Object[thisObject].force.x#
			if thisFX# = 0.0
				thisSX# = V2Object[thisObject].speed.x#
			else
				thisIsMoving = 1
				thisSX# = V2Object[thisObject].speed.x# + thisFX# * thisTime#
				V2Object[thisObject].speed.x# = thisSX#
			endif
			thisFY# = V2Object[thisObject].force.y#
			if thisFY# = 0.0
				thisSY# = V2Object[thisObject].speed.y#
			else
				thisIsMoving = 1
				thisSY# = V2Object[thisObject].speed.y# + thisFY# * thisTime#
				V2Object[thisObject].speed.y# = thisSY#
			endif
			// Apply Speed
			if thisSX# = 0.0
				thisPX# = V2Object[thisObject].pos.x#
			else
				thisIsMoving = 1
				thisPX# = V2Object[thisObject].pos.x# + thisSX# * thisTime#
				V2Object[thisObject].pos.x# = thisPX#
			endif
			if thisSY# = 0.0
				thisPY# = V2Object[thisObject].pos.y#
			else
				thisIsMoving = 1
				thisPY# = V2Object[thisObject].pos.y# + thisSY# * thisTime#
				V2Object[thisObject].pos.y# = thisPY#
			endif
			// Calculate actual speed
			thisSR# = Vect2_GetRadius( thisSX# , thisSY# )
			V2Object[thisObject].speed.r# = thisSR#
			// Calculate actual heading
			thisSA# = Vect2_TargetAngleR( thisSX# , thisSY# , thisSR# )
			V2Object[thisObject].speed.a# = thisSA#

// Calculate polar coordinates
			thisPR# = Vect2_GetRadius( thisPX# , thisPY# )
			V2Object[thisObject].pos.r# = thisPR#
			thisPA# = Vect2_TargetAngleR( thisPX# , thisPY# , thisPR# )
			V2Object[thisObject].pos.a# = thisPA#

// Move Debug Sprites
			thisSprite = V2Object[thisObject].debugSpriteS
			if thisSprite > 0
				thisWidth# = thisSR# * thisZoom#
				setSpriteSize( thisSprite , thisWidth# , thisHeight# )
				setSpriteOffset( thisSprite , 0.0 , thisHeight# * 0.5 )
				setSpritePositionByOffset( thisSprite , thisPX# , thisPY# )
				setSpriteAngle( thisSprite , thisSA# )
				setSpriteColor( thisSprite , 0 , 255 , 0 , 255 )
			endif
			thisSprite = V2Object[thisObject].debugSpriteF
			if thisSprite > 0
				thisFR# = V2Object[thisObject].force.r#
				thisFA# = V2Object[thisObject].force.a# + 180.0
				thisWidth# = thisFR# * thisZoom#
				setSpriteSize( thisSprite , thisWidth# , thisHeight# )
				setSpriteOffset( thisSprite , 0.0 , thisHeight# * 0.5 )
				setSpritePositionByOffset( thisSprite , thisPX# , thisPY# )
				setSpriteAngle( thisSprite , thisFA# )
				setSpriteColor( thisSprite , random( 0, 255 ) , random( 0, 255 ) , random( 0, 255 ) , 255 )
			endif
			V2Object[thisObject].isMoving = thisIsMoving
		endif
	next thisObject
endfunction

+ Code Snippet

function Vect2_Update( thisTime# )
	// Updates Vector2 Objects based on time
	thisZoom# = 1.0 / getViewZoom()
	thisHeight# = thisZoom# * 2.0
	for thisObject = 0 to V2Control.topObject
		if V2Object[thisObject].isLive and V2Object[thisObject].isMoving
			// Apply Force
			thisIsMoving = 0
			thisFX# = V2Object[thisObject].force.x#
			if thisFX# = 0.0
				thisSX# = V2Object[thisObject].speed.x#
			else
				thisIsMoving = 1
				thisSX# = V2Object[thisObject].speed.x# + thisFX# * thisTime#
				V2Object[thisObject].speed.x# = thisSX#
			endif
			thisFY# = V2Object[thisObject].force.y#
			if thisFY# = 0.0
				thisSY# = V2Object[thisObject].speed.y#
			else
				thisIsMoving = 1
				thisSY# = V2Object[thisObject].speed.y# + thisFY# * thisTime#
				V2Object[thisObject].speed.y# = thisSY#
			endif
			// Apply Speed
			if thisSX# = 0.0
				thisPX# = V2Object[thisObject].pos.x#
			else
				thisIsMoving = 1
				thisPX# = V2Object[thisObject].pos.x# + thisSX# * thisTime#
				V2Object[thisObject].pos.x# = thisPX#
			endif
			if thisSY# = 0.0
				thisPY# = V2Object[thisObject].pos.y#
			else
				thisIsMoving = 1
				thisPY# = V2Object[thisObject].pos.y# + thisSY# * thisTime#
				V2Object[thisObject].pos.y# = thisPY#
			endif
			// Calculate actual speed
			thisSR# = Vect2_GetRadius( thisSX# , thisSY# )
			V2Object[thisObject].speed.r# = thisSR#
			// Calculate actual heading
			thisSA# = Vect2_TargetAngleR( thisSX# , thisSY# , thisSR# )
			V2Object[thisObject].speed.a# = thisSA#

			// Calculate polar coordinates
			thisPR# = Vect2_GetRadius( thisPX# , thisPY# )
			V2Object[thisObject].pos.r# = thisPR#
			thisPA# = Vect2_TargetAngleR( thisPX# , thisPY# , thisPR# )
			V2Object[thisObject].pos.a# = thisPA#

			// Move Debug Sprites
			thisSprite = V2Object[thisObject].debugSpriteS
			if thisSprite > 0
				thisWidth# = thisSR# * thisZoom#
				setSpriteSize( thisSprite , thisWidth# , thisHeight# )
				setSpriteOffset( thisSprite , 0.0 , thisHeight# * 0.5 )
				setSpritePositionByOffset( thisSprite , thisPX# , thisPY# )
				setSpriteAngle( thisSprite , thisSA# )
				setSpriteColor( thisSprite , 0 , 255 , 0 , 255 )
			endif
			thisSprite = V2Object[thisObject].debugSpriteF
			if thisSprite > 0
				thisFR# = V2Object[thisObject].force.r#
				thisFA# = V2Object[thisObject].force.a# + 180.0
				thisWidth# = thisFR# * thisZoom#
				setSpriteSize( thisSprite , thisWidth# , thisHeight# )
				setSpriteOffset( thisSprite , 0.0 , thisHeight# * 0.5 )
				setSpritePositionByOffset( thisSprite , thisPX# , thisPY# )
				setSpriteAngle( thisSprite , thisFA# )
				setSpriteColor( thisSprite , random( 0, 255 ) , random( 0, 255 ) , random( 0, 255 ) , 255 )
			endif
			V2Object[thisObject].isMoving = thisIsMoving
		endif
	next thisObject
endfunction

and here are some functions used by the loop

function Vect2_GetRadius( offsetX# , offsetY# )
	if offsetX# = 0.0 and offsetY# = 0.0
		offsetR# = 0.0
	elseif offsetX# = 0.0
		offsetR# = abs( offsetY# )
	elseif offsetY# = 0.0
		offsetR# = abs( offsetX# )
	else
		offsetR# = sqrt( offsetX# * offsetX# + offsetY# * offsetY# )
	endif
endfunction offsetR#

function Vect2_TargetAngle( offsetX# , offsetY# )
	offsetR# = Vect2_GetRadius( offsetX# , offsetY# )
	thisAngle# = Vect2_TargetAngleR( offsetX# , offsetY# , offsetR# )
endfunction thisAngle#

function Vect2_TargetAngleR( offsetX# , offsetY# , offsetR# )
	if offsetR# = 0.0
		thisAngle# = 0.0
	elseif offsetY# > 0.0
		thisAngle# = acos( offsetX# / offsetR# )
	elseif offsetY# < 0.0
		thisAngle# = 360.0 - acos( offsetX# / offsetR# )
	elseif offsetX# > 0.0
		thisAngle# = 0.0
	elseif offsetX# < 0.0
		thisAngle# = 180.0
	else
		// should never happen
		thisAngle# = 0.0
	endif
endfunction thisAngle#

function Vect2_AddObject()
	thisObject = Vect2_FindFreeObject()
	if thisObject > 0
		if thisObject > V2Control.topObject then V2Control.topObject = thisObject
		V2Object[thisObject].isLive = 1
		V2Object[thisObject].isMoving = 0
		thisCoord as V2CoordTypeF
		thisCoord = Vect2_NewCoordF()
		V2Object[thisObject].pos = thisCoord
		V2Object[thisObject].speed = thisCoord
		V2Object[thisObject].force = thisCoord
	endif
endfunction thisObject

function Vect2_FindFreeObject()
	for thisObject = 1 to V2Control.topObject
		if V2Object[thisObject].isLive = 0 then exit
	next thisObject
	if thisObject > V2_MAX_OBJECTS then thisObject = 0
endfunction thisObject

function Vect2_ZeroForce( thisObject )
	if thisObject > 0 and thisObject <= V2Control.topObject
		V2Object[thisObject].force.r# = 0
		V2Object[thisObject].force.a# = 0
		V2Object[thisObject].force.x# = 0
		V2Object[thisObject].force.y# = 0
	endif
endfunction

function Vect2_ZeroSpeed( thisObject )
	if thisObject > 0 and thisObject <= V2Control.topObject
		V2Object[thisObject].speed.r# = 0
		V2Object[thisObject].speed.a# = 0
		V2Object[thisObject].speed.x# = 0
		V2Object[thisObject].speed.y# = 0
	endif
endfunction

function Vect2_ZeroAll( thisObject )
	if thisObject > 0 and thisObject <= V2Control.topObject
		Vect2_ZeroSpeed( thisObject )
		Vect2_ZeroForce( thisObject )
		V2Object[thisObject].isMoving = 0
	endif
endfunction

function Vect2_SetPolarForce( thisObject , thisForce# , thisAngle# )
	if thisObject > 0 and thisObject <= V2Control.topObject
		V2Object[thisObject].force.r# = thisForce#
		V2Object[thisObject].force.a# = thisAngle#
		if thisForce# = 0.0
			V2Object[thisObject].force.x# = 0.0
			V2Object[thisObject].force.y# = 0.0
		else
			V2Object[thisObject].isMoving = 1
			V2Object[thisObject].force.x# = thisForce# * cos( thisAngle# )
			V2Object[thisObject].force.y# = thisForce# * sin( thisAngle# )
		endif
	endif
endfunction

function Vect2_SetPolarSpeed( thisObject , thisSpeed# , thisAngle# )
	if thisObject > 0 and thisObject <= V2Control.topObject
		if thisSpeed# = 0.0
			V2Object[thisObject].speed.x# = 0.0
			V2Object[thisObject].speed.y# = 0.0
		else
			V2Object[thisObject].isMoving = 1
			V2Object[thisObject].speed.x# = thisSpeed# * cos( thisAngle# )
			V2Object[thisObject].speed.y# = thisSpeed# * sin( thisAngle# )
		endif
	endif
endfunction

function Vect2_SetPolarPos( thisObject , thisRadius# , thisAngle# )
	if thisObject > 0 and thisObject <= V2Control.topObject
		if thisRadius# = 0.0
			V2Object[thisObject].pos.x# = 0.0
			V2Object[thisObject].pos.y# = 0.0
		else
			V2Object[thisObject].pos.x# = thisRadius# * cos( thisAngle# )
			V2Object[thisObject].pos.y# = thisRadius# * sin( thisAngle# )
		endif
	endif
endfunction

function Vect2_SetCartPos( thisObject , thisX# , thisY# )
	if thisObject > 0 and thisObject <= V2Control.topObject
		V2Object[thisObject].pos.x# = thisX#
		V2Object[thisObject].pos.y# = thisY#
	endif
endfunction

function Vect2_AngleForSprite( thisAngle# )
	thisAngle# = WrapAngleFloat( thisAngle# + 90 )
endfunction thisAngle#

+ Code Snippet

function Vect2_GetRadius( offsetX# , offsetY# )
	if offsetX# = 0.0 and offsetY# = 0.0
		offsetR# = 0.0
	elseif offsetX# = 0.0
		offsetR# = abs( offsetY# )
	elseif offsetY# = 0.0
		offsetR# = abs( offsetX# )
	else
		offsetR# = sqrt( offsetX# * offsetX# + offsetY# * offsetY# )
	endif
endfunction offsetR#

function Vect2_TargetAngle( offsetX# , offsetY# )
	offsetR# = Vect2_GetRadius( offsetX# , offsetY# )
	thisAngle# = Vect2_TargetAngleR( offsetX# , offsetY# , offsetR# )
endfunction thisAngle#

function Vect2_TargetAngleR( offsetX# , offsetY# , offsetR# )
	if offsetR# = 0.0
		thisAngle# = 0.0
	elseif offsetY# > 0.0
		thisAngle# = acos( offsetX# / offsetR# )
	elseif offsetY# < 0.0
		thisAngle# = 360.0 - acos( offsetX# / offsetR# )
	elseif offsetX# > 0.0
		thisAngle# = 0.0
	elseif offsetX# < 0.0
		thisAngle# = 180.0
	else
		// should never happen
		thisAngle# = 0.0
	endif
endfunction thisAngle#

function Vect2_AddObject()
	thisObject = Vect2_FindFreeObject()
	if thisObject > 0
		if thisObject > V2Control.topObject then V2Control.topObject = thisObject
		V2Object[thisObject].isLive = 1
		V2Object[thisObject].isMoving = 0
		thisCoord as V2CoordTypeF
		thisCoord = Vect2_NewCoordF()
		V2Object[thisObject].pos = thisCoord
		V2Object[thisObject].speed = thisCoord
		V2Object[thisObject].force = thisCoord
	endif
endfunction thisObject

function Vect2_FindFreeObject()
	for thisObject = 1 to V2Control.topObject
		if V2Object[thisObject].isLive = 0 then exit
	next thisObject
	if thisObject > V2_MAX_OBJECTS then thisObject = 0
endfunction thisObject

function Vect2_ZeroForce( thisObject )
	if thisObject > 0 and thisObject <= V2Control.topObject
		V2Object[thisObject].force.r# = 0
		V2Object[thisObject].force.a# = 0
		V2Object[thisObject].force.x# = 0
		V2Object[thisObject].force.y# = 0
	endif
endfunction

function Vect2_ZeroSpeed( thisObject )
	if thisObject > 0 and thisObject <= V2Control.topObject
		V2Object[thisObject].speed.r# = 0
		V2Object[thisObject].speed.a# = 0
		V2Object[thisObject].speed.x# = 0
		V2Object[thisObject].speed.y# = 0
	endif
endfunction

function Vect2_ZeroAll( thisObject )
	if thisObject > 0 and thisObject <= V2Control.topObject
		Vect2_ZeroSpeed( thisObject )
		Vect2_ZeroForce( thisObject )
		V2Object[thisObject].isMoving = 0
	endif
endfunction

function Vect2_SetPolarForce( thisObject , thisForce# , thisAngle# )
	if thisObject > 0 and thisObject <= V2Control.topObject
		V2Object[thisObject].force.r# = thisForce#
		V2Object[thisObject].force.a# = thisAngle#
		if thisForce# = 0.0
			V2Object[thisObject].force.x# = 0.0
			V2Object[thisObject].force.y# = 0.0
		else
			V2Object[thisObject].isMoving = 1
			V2Object[thisObject].force.x# = thisForce# * cos( thisAngle# )
			V2Object[thisObject].force.y# = thisForce# * sin( thisAngle# )
		endif
	endif
endfunction

function Vect2_SetPolarSpeed( thisObject , thisSpeed# , thisAngle# )
	if thisObject > 0 and thisObject <= V2Control.topObject
		if thisSpeed# = 0.0
			V2Object[thisObject].speed.x# = 0.0
			V2Object[thisObject].speed.y# = 0.0
		else
			V2Object[thisObject].isMoving = 1
			V2Object[thisObject].speed.x# = thisSpeed# * cos( thisAngle# )
			V2Object[thisObject].speed.y# = thisSpeed# * sin( thisAngle# )
		endif
	endif
endfunction

function Vect2_SetPolarPos( thisObject , thisRadius# , thisAngle# )
	if thisObject > 0 and thisObject <= V2Control.topObject
		if thisRadius# = 0.0
			V2Object[thisObject].pos.x# = 0.0
			V2Object[thisObject].pos.y# = 0.0
		else
			V2Object[thisObject].pos.x# = thisRadius# * cos( thisAngle# )
			V2Object[thisObject].pos.y# = thisRadius# * sin( thisAngle# )
		endif
	endif
endfunction

function Vect2_SetCartPos( thisObject , thisX# , thisY# )
	if thisObject > 0 and thisObject <= V2Control.topObject
		V2Object[thisObject].pos.x# = thisX#
		V2Object[thisObject].pos.y# = thisY#
	endif
endfunction

function Vect2_AngleForSprite( thisAngle# )
	thisAngle# = WrapAngleFloat( thisAngle# + 90 )
endfunction thisAngle#

It's stripped out of a project, there should be enough to get something going - I hope you can make sense of it.

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