Problem with SetSpriteShapeBox - GameCreators Forum

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Max Tillberg

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Posted: 3rd Sep 2013 15:28 Edited at: 3rd Sep 2013 15:30

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I wonder if someone could help me with the SetSpriteShapeBox command? For some reason it is centered at the middle of sprites and I wonder if it should. The problem is that it gets quite hard to calculate the angle.

If I tries the following, the box is offset from the sprite

+ Code Snippet

SetSpriteShapeBox( i, 0, 0, GetSpriteWidth(i), GetSpriteHeight(i), GetSpriteAngleRad( i ) )

This works better but the angle is off since the instert point differs.

+ Code Snippet

SetSpriteShapeBox( i, -1*(GetSpriteWidth(i)/2), -1*(GetSpriteHeight(i)/2), GetSpriteWidth(i)/2, GetSpriteHeight(i)/2, GetSpriteAngleRad( i ) )

I use the latest beta and Tier 1.

Sincerely,
Max Tillberg

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Markus

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Posted: 3rd Sep 2013 15:43

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i think the shape is set for non rotated sprites because it rotates with the sprite. the angle is a optional shift if the image is rotated.

the shape its centered by default.
there exists also a simple box shape command.
SetSpriteShape( iSpriteIndex, shape )
0=no shape, 1=circle, 2=box, 3=polygon

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Max Tillberg

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Posted: 3rd Sep 2013 15:55

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According to the help file "The box is defined by specifying its top left and bottom right coordinates in sprite space, relative to the top left corner of the sprite." Does not this indicate the the insert point is top left and not center of the sprite? The reason I can't use SetSpriteShape is that I want the physics box to be smaller than the sprite. I guess I could recalculate the angle myself but it is not that easy.

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Max Tillberg

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baxslash

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Posted: 3rd Sep 2013 16:04

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I actually reported this issue to Paul quite some time ago and he fixed it. My guess is that somehow the bug has crept back in. I will send him an email.

"Everything should be made as simple as possible, but not simpler."

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Max Tillberg

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Posted: 3rd Sep 2013 16:11

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Thanks a lot. I guess AppGameKit still have some issues but hopefully it will get out of beta soon.

Sincerely,
Max Tillberg

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Van B

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Posted: 3rd Sep 2013 16:12

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Might be easier specifying lines instead of the box, like the box sides in turn - then you can offset them however you like, even have an irregular box if you need it, or specify a more ideal shape for the sprite.

I am the one who knocks...

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baxslash

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Posted: 3rd Sep 2013 16:36

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In the above case you could just use:

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SetSpriteShape( iSpriteIndex, 2 ) `where 2 is box shape

The only time you need the other version is if you are using a none bounding box shape...

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Max Tillberg

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Posted: 3rd Sep 2013 16:36 Edited at: 3rd Sep 2013 16:37

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Van B, When you say "specifying lines", are you thinking of addSpriteShapePolygon or is there some other method?

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Max Tillberg

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baxslash

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Posted: 3rd Sep 2013 16:43

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I think that's what VanB means. This got me thinking though, have you tried using AddSpriteShapeBox rather than SetSpriteShapeBox? (You might have to SetSpriteShape(spriteID, 0) first)

I wonder if it was the Add command Paul fixed rather than the Set command (which deletes existing shapes on a sprite before creating a new one).

"Everything should be made as simple as possible, but not simpler."

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Max Tillberg

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Posted: 3rd Sep 2013 16:58

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I have the same problem with AddSpriteShapeBox (centered) plus I end up with two boxes even if I don't use SetSpriteShape. I tried to ClearSpriteShapes but only the manually added sprite is removed.

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Max Tillberg

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baxslash

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Posted: 3rd Sep 2013 17:18

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Max Tillberg, can you post some example code?

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Max Tillberg

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Posted: 3rd Sep 2013 17:54

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Sure thing, here is the complete code

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SetVirtualResolution( GetDeviceWidth(), GetDeviceHeight() )

CreateSprite ( 1, LoadImage ( "blue.png" ) )
CreateSprite ( 2, LoadImage ( "blue.png" ) )

SetSpritePosition ( 1, 10, 10 )
SetSpriteAngle( 1, 30 )
SetSpritePosition ( 2, 100, 100 )
SetSpriteAngle( 2, 30 )


SetPhysicsDebugOn()
//This should work but it does not
SetSpritePhysicsOn ( 1, 1 )
SetSpriteShapeBox( 1, 0, 0, GetSpriteWidth(1), GetSpriteHeight(1), GetSpriteAngleRad(1) )
//This almost work but the angle is wrong
SetSpritePhysicsOn ( 2, 1 )
SetSpriteShapeBox( 2, -1*(GetSpriteWidth(2)/2), -1*(GetSpriteHeight(2)/2), GetSpriteWidth(2)/2, GetSpriteHeight(2)/2, GetSpriteAngleRad(2) )

do
    Sync ( )
loop

Sincerely,
Max Tillberg

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baxslash

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Posted: 3rd Sep 2013 18:07

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This needs changing: GetSpriteAngleRad(1)
To this: GetSpriteAngle(1)

Can you post a screenshot, I haven't got AppGameKit at work and freedom engine seems to not display debug...

"Everything should be made as simple as possible, but not simpler."

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Paul Johnston

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Posted: 3rd Sep 2013 18:27 Edited at: 3rd Sep 2013 18:29

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The help files are incorrect in this case, the box is now relative to the offset point rather than the top left corner. However the angle parameter is handled by Box2D which always rotates the box around its center.

This only matters if you want the box to be at a different angle than the sprite since it will still rotate with the sprite. It seems in this case you want the box to line up with the sprite by using GetSpriteAngle, this is not necessary and an angle of 0 should line it up.

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Max Tillberg

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Posted: 3rd Sep 2013 18:32 Edited at: 3rd Sep 2013 18:33

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I changed to GetSpriteAngle in a third example but I am rather sure the angle should be in degrees. Anyway, the angle is still wrong.

+ Code Snippet

SetVirtualResolution( GetDeviceWidth(), GetDeviceHeight() )

CreateSprite ( 1, LoadImage ( "blue.png" ) )
CreateSprite ( 2, LoadImage ( "blue.png" ) )
CreateSprite ( 3, LoadImage ( "blue.png" ) )

SetSpritePosition ( 1, 10, 10 )
SetSpriteAngle( 1, 45 )
SetSpritePosition ( 2, 100, 100 )
SetSpriteAngle( 2, 45 )
SetSpritePosition ( 3, 200, 200 )
SetSpriteAngle( 3, 45 )

SetPhysicsDebugOn()
//This should work but it does not
SetSpritePhysicsOn ( 1, 1 )
SetSpriteShapeBox( 1, 0, 0, GetSpriteWidth(1), GetSpriteHeight(1), GetSpriteAngleRad(1) )
//This almost work but the angle is wrong
SetSpritePhysicsOn ( 2, 1 )
SetSpriteShapeBox( 2, -1*(GetSpriteWidth(2)/2), -1*(GetSpriteHeight(2)/2), GetSpriteWidth(2)/2, GetSpriteHeight(2)/2, GetSpriteAngleRad(2) )
//Same thing but angle in degrees
SetSpritePhysicsOn ( 3, 1 )
SetSpriteShapeBox( 3, -1*(GetSpriteWidth(3)/2), -1*(GetSpriteHeight(3)/2), GetSpriteWidth(3)/2, GetSpriteHeight(3)/2, GetSpriteAngle(3) )

do
    Sync ( )
loop

Sincerely,
Max Tillberg

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Max Tillberg

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Posted: 3rd Sep 2013 18:41

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Thanks Paul,
There is still two things that I do not understand. I have not changed the offset, should it not 0,0 be in the upper left corner of the sprites. I am rather sure that in my example it is in the middle of the first sprite. My second question is how I set the angle in SetSpriteShapeBox so it is alligned to the sprite?

Sincerely,
Max Tillberg

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baxslash

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Posted: 3rd Sep 2013 19:01

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Quote: "There is still two things that I do not understand. I have not changed the offset, should it not 0,0 be in the upper left corner of the sprites. I am rather sure that in my example it is in the middle of the first sprite."

No, the offset is in the centre of the sprite by default.

Quote: "My second question is how I set the angle in SetSpriteShapeBox so it is alligned to the sprite?"

The angle should be zero as it is relative to the sprite not the world.

"Everything should be made as simple as possible, but not simpler."

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Markus

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Posted: 3rd Sep 2013 19:12

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+ Code Snippet

rem
rem AGK Application 108B15
rem


SetVirtualResolution( GetDeviceWidth(), GetDeviceHeight() )

img=loadimage("bitmap.bmp")
CreateSprite ( 1, img )
CreateSprite ( 2, img )
CreateSprite ( 3, img )
setspritesize(1,20,20)
setspritesize(2,20,20)
setspritesize(3,20,20)

SetSpritePosition ( 1, 10, 10 )
SetSpriteAngle( 1, 45 )
SetSpritePosition ( 2, 100, 100 )
SetSpriteAngle( 2, 45+10 )
SetSpritePosition ( 3, 200, 200 )
SetSpriteAngle( 3, 45+20 )

SetPhysicsDebugOn()

SetSpritePhysicsOn ( 1, 1 )
ShapeBox(1)

SetSpritePhysicsOn ( 2, 1 )
ShapeBox(2)

SetSpritePhysicsOn ( 3, 1 )
ShapeBox(3)

do
    Sync ( )
loop

function ShapeBox(nr)

    SetSpriteShapeBox( nr, -GetSpriteWidth(nr)/2.0, -GetSpriteHeight(nr)/2.0, GetSpriteWidth(nr)/2.0, GetSpriteHeight(nr)/2.0, 0 )

endfunction

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Max Tillberg

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Posted: 3rd Sep 2013 19:15

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Thanks a lot everybody, now it works.

Sincerely,
Max Tillberg

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AppGameKit Classic Chat / Problem with SetSpriteShapeBox