Quaternions / rotation problem using FixObjectToObject()

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PSY

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7

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Joined: 3rd Jul 2016

Location: Laniakea Supercluster

Posted: 27th Jan 2024 00:07 Edited at: 27th Jan 2024 00:08

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Hey guys,

I'm having trouble understanding rotation after using FixObjectToObject().

In the following example, Earth rotates around the Sun.
I also attached the complete project with the media files as .zip.
There's no copyright issue with the .png files!

#option_explicit

type ObjectType
	gfx	as integer
	ID	as integer
	x	as float
	y	as float
	z	as float
endtype

global sun 		as ObjectType
global earth		as ObjectType

SetWindowSize 		( 0, 0, 1 )
SetSyncRate 			( 144, 1 )
SetDisplayAspect		( GetMaxDeviceWidth() * 1.0 / GetMaxDeviceHeight() )
SetRawMouseVisible	( 0 )
SetCameraPosition	( 1, 0, 0, -100 )
SetCameraRange		( 1, 1, 1000 )
SetCameraLookAt		( 1, 0, 0, 0, 0 )
SetRawMouseVisible	( 0 )

// sun
sun.gfx					= LoadImage ( "sun.png" )
sun.ID					= CreateObjectSphere ( 5.0 , 64, 64 )
sun.x 					= 0.0
sun.y 					= 0.0
sun.z					= 0.0
SetObjectPosition		( sun.ID, sun.x, sun.y, sun.z )
SetObjectImage			( sun.ID, sun.gfx, 0 )
SetObjectColorEmissive	( sun.ID, 155, 155, 0 )
		
// earth		
earth.y				= 20.0
earth.gfx 			= LoadImage ( "earth_day.png" )
earth.ID			= CreateObjectSphere ( 10.0, 64, 64 )
SetObjectImage		( earth.ID, earth.gfx, 0 )
SetObjectPosition	( earth.ID, earth.x, earth.y, earth.z )

// create pivot
FixObjectToObject	( earth.ID, sun.ID )

repeat
	RotateObjectlocalZ 		( sun.ID, 0.5 )
	SetObjectRotationQuat	( earth.ID, 0, 0, 0, 0 )
	RotateObjectlocalY 		( earth.ID, 5.0 )

Sync()
	
until GetRawKeyPressed ( 27 )
END

+ Code Snippet

#option_explicit

type ObjectType
	gfx	as integer
	ID	as integer
	x	as float
	y	as float
	z	as float
endtype	

global sun 		as ObjectType
global earth		as ObjectType


SetWindowSize 		( 0, 0, 1 )
SetSyncRate 			( 144, 1 )
SetDisplayAspect		( GetMaxDeviceWidth() * 1.0 / GetMaxDeviceHeight() )
SetRawMouseVisible	( 0 )
SetCameraPosition	( 1, 0, 0, -100 )
SetCameraRange		( 1, 1, 1000 )
SetCameraLookAt		( 1, 0, 0, 0, 0 )
SetRawMouseVisible	( 0 )


// sun
sun.gfx					= LoadImage ( "sun.png" )
sun.ID					= CreateObjectSphere ( 5.0 , 64, 64 )
sun.x 					= 0.0
sun.y 					= 0.0
sun.z					= 0.0
SetObjectPosition		( sun.ID, sun.x, sun.y, sun.z )
SetObjectImage			( sun.ID, sun.gfx, 0 )
SetObjectColorEmissive	( sun.ID, 155, 155, 0 )
		
// earth		
earth.y				= 20.0
earth.gfx 			= LoadImage ( "earth_day.png" )
earth.ID			= CreateObjectSphere ( 10.0, 64, 64 )
SetObjectImage		( earth.ID, earth.gfx, 0 )
SetObjectPosition	( earth.ID, earth.x, earth.y, earth.z )

// create pivot
FixObjectToObject	( earth.ID, sun.ID )	



repeat
	RotateObjectlocalZ 		( sun.ID, 0.5 )
	SetObjectRotationQuat	( earth.ID, 0, 0, 0, 0 )
	RotateObjectlocalY 		( earth.ID, 5.0 )

	Sync()
	
until GetRawKeyPressed ( 27 )
END

I used

+ Code Snippet

SetObjectRotationQuat ( earth.ID, 0, 0, 0, 0 )

to rotate Earth back to its default angle.
That worked, but after using the Quat command I'm unable to rotate Earth using

+ Code Snippet

RotateObjectlocalY ( earth.ID, 5.0 )

If I comment the Quat command,

+ Code Snippet

RotateObjectlocalY ( earth.ID, 5.0 )

works, but Earth angles are useless due to the Sun - Earth pivot.

Can anybody explain why the Euler rotation doesn't work anymore after setting the Quat rotation?
I can fix the problem by calculating the Earth orbit with sin and cos, but I want to understand what's going on.

Thanks!
PSY

PSY LABS Games
Coders don't die, they just gosub without return

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PSY

Developer

7

Years of Service

User Offline

Joined: 3rd Jul 2016

Location: Laniakea Supercluster

Posted: 27th Jan 2024 03:17 Edited at: 27th Jan 2024 03:21

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This post has been marked by the post author as the answer.

I managed to get the code running by using the pivot method, but without using Quaternions.
I simply rotate Earth back around the Z axis by the same amount it was turned by using the pivot.
Then I rotate Earth around Y.
Just use the media files from the above post.

#option_explicit
 
type ObjectType
    gfx as integer
    ID  as integer
    x   as float
    y   as float
    z   as float
endtype
 
global sun   		as ObjectType
global earth			as ObjectType
global angle			as float
global pivot_angle	as float 
 
SetWindowSize       ( 0, 0, 1 )
SetSyncRate         ( 144, 1 )
SetDisplayAspect    ( GetMaxDeviceWidth() * 1.0 / GetMaxDeviceHeight() )
SetRawMouseVisible  ( 0 )
SetCameraPosition   ( 1, 0, 0, -100 )
SetCameraRange      ( 1, 1, 1000 )
SetCameraLookAt     ( 1, 0, 0, 0, 0 )
SetRawMouseVisible  ( 0 )
 
 
// sun
sun.gfx                 = LoadImage ( "sun.png" )
sun.ID                  = CreateObjectSphere ( 5.0 , 64, 64 )
sun.x                   = 0.0
sun.y                   = 0.0
sun.z                   = 0.0
SetObjectPosition       ( sun.ID, sun.x, sun.y, sun.z )
SetObjectImage          ( sun.ID, sun.gfx, 0 )
SetObjectColorEmissive  ( sun.ID, 155, 155, 0 )
         
// earth        
earth.y             = 20.0
earth.gfx           = LoadImage ( "earth_day.png" )
earth.ID            = CreateObjectSphere ( 10.0, 64, 64 )
SetObjectImage      ( earth.ID, earth.gfx, 0 )
SetObjectPosition   ( earth.ID, earth.x, earth.y, earth.z )

// create pivot
FixObjectToObject   ( earth.ID, sun.ID )

repeat
	angle = fmod ( angle + 1.0, 360.0 )		// used for Earth Y Rotation
	RotateObjectlocalZ ( sun.ID, .5 )		// rotate pivot
	pivot_angle = atan2 ( GetObjectWorldY ( earth.ID ) - sun.y, GetObjectWorldX (earth.ID) - sun.x ) 	// calculate pivot angle
	SetObjectRotation ( earth.ID, 0, 0, 90 - pivot_angle )	// rotate Earth back around Z using pivot angle
   	RotateObjectlocalY ( earth.ID, angle )	// rotate Earth around Y
   
    Sync()
     
until GetRawKeyPressed ( 27 )
END

+ Code Snippet

#option_explicit
 
type ObjectType
    gfx as integer
    ID  as integer
    x   as float
    y   as float
    z   as float
endtype
 
global sun   		as ObjectType
global earth			as ObjectType
global angle			as float
global pivot_angle	as float 
 
SetWindowSize       ( 0, 0, 1 )
SetSyncRate         ( 144, 1 )
SetDisplayAspect    ( GetMaxDeviceWidth() * 1.0 / GetMaxDeviceHeight() )
SetRawMouseVisible  ( 0 )
SetCameraPosition   ( 1, 0, 0, -100 )
SetCameraRange      ( 1, 1, 1000 )
SetCameraLookAt     ( 1, 0, 0, 0, 0 )
SetRawMouseVisible  ( 0 )
 
 
// sun
sun.gfx                 = LoadImage ( "sun.png" )
sun.ID                  = CreateObjectSphere ( 5.0 , 64, 64 )
sun.x                   = 0.0
sun.y                   = 0.0
sun.z                   = 0.0
SetObjectPosition       ( sun.ID, sun.x, sun.y, sun.z )
SetObjectImage          ( sun.ID, sun.gfx, 0 )
SetObjectColorEmissive  ( sun.ID, 155, 155, 0 )
         
// earth        
earth.y             = 20.0
earth.gfx           = LoadImage ( "earth_day.png" )
earth.ID            = CreateObjectSphere ( 10.0, 64, 64 )
SetObjectImage      ( earth.ID, earth.gfx, 0 )
SetObjectPosition   ( earth.ID, earth.x, earth.y, earth.z )


// create pivot
FixObjectToObject   ( earth.ID, sun.ID )    
 

repeat
	angle = fmod ( angle + 1.0, 360.0 )		// used for Earth Y Rotation
	RotateObjectlocalZ ( sun.ID, .5 )		// rotate pivot
	pivot_angle = atan2 ( GetObjectWorldY ( earth.ID ) - sun.y, GetObjectWorldX (earth.ID) - sun.x ) 	// calculate pivot angle
	SetObjectRotation ( earth.ID, 0, 0, 90 - pivot_angle )	// rotate Earth back around Z using pivot angle
   	RotateObjectlocalY ( earth.ID, angle )	// rotate Earth around Y
   
    Sync()
     
until GetRawKeyPressed ( 27 )
END

But I still wonder why I cant use Euler rotation after using SetObjectRotationQuat ( earth.ID, 0, 0, 0, 0 )...
I know I didn't increase the angle in the first code, but that doesn't matter at all. I simply can't rotate Euler after using Quat rotation.

PSY

PSY LABS Games
Coders don't die, they just gosub without return

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Globbits

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Joined: 30th Jan 2009

Location: Cambridge

Posted: 22nd Feb 2024 11:16

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I think the code you're using:

+ Code Snippet

SetObjectRotationQuat ( earth.ID, 0, 0, 0, 0 )

Should be

+ Code Snippet

SetObjectRotationQuat ( earth.ID, 1, 0, 0, 0 )

The default value of W is 1, not 0

I hope this helps.

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PSY

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Joined: 3rd Jul 2016

Location: Laniakea Supercluster

Posted: 22nd Feb 2024 15:54

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Nope, that makes it even worse

Thanks for trying though

Maybe I'll have a look at it another day. I solved the problem without having to use quaternions, so it's all good

PSY LABS Games
Coders don't die, they just gosub without return

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blink0k

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Joined: 22nd Feb 2013

Location: the land of oz

Posted: 22nd Feb 2024 19:22

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I found that using RotateLocal would cause the object to "flip" when the Y rotation crossed the X axis. I solved this by saving the x/yz rotation values and using SetObjectRotation()

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AppGameKit Studio Chat / [SOLVED] Quaternions / rotation problem using FixObjectToObject()

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