Inside object?

Blitz3D Forums/Blitz3D Programming/Inside object?

Guy Fawkes

(Posted 2012) [#1]

Hi all, I was looking into how I could play some music for each "zone" my character is in. I found this old code called CreateOBB. I've managed to modify it to not look horrible.

Problem is, I think the math is off... The player won't stay green for the WHOLE inside of the object...

Here's the code:

; This lib allows you to create and configure an OBB, and then test if a point or an entity has intruded into the OBB's space.

; An OBB is an Oriented Bounding Box. It is not locked to the dimensional axiis and consequently can be rotated.
; An AABB is an Axially Aligned Bounding Box. It is aligned to the dimensional axiis and consequently cannot be rotated.

; Note that an OBB is really just an AABB that exists in a different coordinate space. To test if a point has intruded into an OBB's space, you transform the point into the OBB's coordinate space and then perform the same box intrusion test that you would use with an AABB.


;_______________________________________________________
; *** EXAMPLE ***



Graphics3D 800, 600, 0, 2
SetBuffer BackBuffer()
HidePointer

Global G_camera = CreateCamera()
CameraRange G_camera,.1,50000
PositionEntity G_camera,0,1,0

AmbientLight 255,255,255

Global G_test_ball = CreateCube()
MoveEntity G_test_ball, 0.0, 0.0, 5.0
PositionEntity G_test_ball,0,1,0

; Create the OBB pivot and set it's transformation data.
Global G_obb = CreateOBB( 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 12.0, 12.0, 12.0 )

; -- Create a cube to display the position of the OBB.
Global G_display_cube = CreateCube( G_obb )
PositionEntity G_display_cube, 0.0, 1.0, 0.0
RotateEntity G_display_cube, 0.0, 0.0, 0.0
ScaleEntity G_display_cube, 12.0, 12.0, 12.0
FlipMesh G_display_cube
EntityAlpha G_display_cube, 0.8
EntityShininess G_display_cube,1
;^^^^^^

sky=CreateCube()
ScaleEntity sky,10000,10000,10000
EntityColor sky,102,102,255
FlipMesh sky

Global land = CreatePlane()
EntityColor land, 0,128,255

Global G_mouse_speed_x#, G_mouse_speed_y#

Local elapsed
Global G_deltatime#
Global G_old_time = MilliSecs()

While Not KeyHit(1)

	Cls
	
	SuperCam(G_camera,G_Test_Ball,.03,8,4,0,0)
	
	py# = EntityY#(G_Test_Ball, True)
	ey# = EntityY#(land, True)
	
	If py#<1.0 Then py# = 1.0
	If py#>2 Then py# = 2

	If ey#<1.0 Then ey# = 1.0
	If ey#>2 Then ey# = 2
	
	PositionEntity G_Test_Ball, EntityX#(G_Test_Ball, True), py#, EntityZ#(G_Test_Ball, True)
	
	MoveEntity G_Test_Ball, 0, (KeyDown(44)-KeyDown(45))*0.002, (KeyDown(17)-KeyDown(31) Or KeyDown(200)-KeyDown(208))*0.002
	
	TurnEntity G_Test_Ball, 0, (KeyDown(30)-KeyDown(32) Or KeyDown(203)-KeyDown(205))*0.05, 0

	; -- Update timing.
	elapsed = MilliSecs() - G_old_time
	If elapsed > 100 Then elapsed = 100
	G_deltatime# = elapsed / 1000.0
	G_old_time = MilliSecs()
	;^^^^^^


	; -- Do the OBB test.
	If EntityInOBB( G_obb, G_test_ball )
		EntityColor G_test_ball, 0.0, 255.0, 0.0
	Else
		EntityColor G_test_ball, 200.0, 0.0, 0.0
	EndIf
	;^^^^^^
	
	UpdateWorld
	RenderWorld
	Color 255,255,255
	Text 10, 10, "Press W, A, S, D, F, C keys to move. Press ESCAPE to exit."
	Text 10, 30, "The ball's color will change from red to green when it intrudes into the OBB."
	Text GraphicsWidth()/2, GraphicsHeight()/2, "X: "+EntityX#(G_Test_Ball, True), 1, 1
	Text GraphicsWidth()/2, GraphicsHeight()/2+20, "Y: "+EntityY#(G_Test_Ball, True), 1, 1
	Text GraphicsWidth()/2, GraphicsHeight()/2+40, "Z: "+EntityZ#(G_Test_Ball, True), 1, 1
	Flip 0
Wend

End

Function SuperCam(cam,ent,cspeed#,dist#,hite#,xrot#,tilt#)
	
	TFormPoint 0,hite#,-dist#,ent,0
	
	cx#=(TFormedX()-EntityX(cam))*cspeed#
	cy#=(TFormedY()-EntityY(cam))*cspeed#
	cz#=(TFormedZ()-EntityZ(cam))*cspeed#
	
	TranslateEntity cam,cx,cy,cz
	PointEntity cam,ent
	RotateEntity cam,xrot#,EntityYaw(cam),tilt#
	
End Function

Function CreateOBB( x#, y#, z#, pitch#, yaw#, roll#, width#, height#, depth#, parent = 0 )
; Creates an OBB and returns its entity handle. Note that an OBB is just a pivot entity.
; The position, rotation, and size of the OBB will be set using the supplied values. Note that these values are initially applied in global space, but will be relative to the parent space after the obb has been created.
; An optional parent entity can be specified. The obb will be attached to this parent, and its position, rotation, and size will update when the position, rotation, and\or size of the parent changes.

	Local obb_pivot = CreatePivot( parent )
	PositionEntity obb_pivot, x#, y#, z#, True
	RotateEntity obb_pivot, pitch#, yaw#, roll#, True
	ScaleEntity obb_pivot, width#, height#, depth#, True
	Return obb_pivot
End Function



Function PointInOBB( obb_pivot, x#, y#, z# )
; Tests if the specified x, y, z, point is inside the space of the specified OBB pivot entity.
; If so, a true result is returned. If not, a false result is returned.

	TFormPoint x#, y#, z#, 0, obb_pivot
	x# = TFormedX() : y# = TFormedY() : z# = TFormedZ()
	If ( x# >= -1.0 ) And ( x# <= 1.0 )
		If ( y# >= -1.0 ) And ( y# <= 1.0 )
			If ( z# >= -1.0 ) And ( z# <= 1.0 )
				Return True
			EndIf
		EndIf
	EndIf
	Return False
End Function



Function EntityInOBB( obb_pivot, entity_to_test )
; Tests if the specified entity to test is inside the space of the specified OBB pivot entity.
; If so, a true result is returned. If not, a false result is returned.

	TFormPoint EntityX#( entity_to_test, True ), EntityY#( entity_to_test, True ), EntityZ#( entity_to_test, True ), 0, obb_pivot
	x# = TFormedX() : y# = TFormedY() : z# = TFormedZ()
	If ( x# >= -1.0 ) And ( x# <= 1.0 )
		If ( y# >= -1.0 ) And ( y# <= 1.0 )
			If ( z# >= -1.0 ) And ( z# <= 1.0 )
				Return True
			EndIf
		EndIf
	EndIf
	Return False
End Function

Any help is greatly appreciated! :)

Thanks! :)

Guy Fawkes

(Posted 2012) [#2]

Bump :)

Stevie G

(Posted 2012) [#3]

Can I ask, did the code work before you modified it?

Guy Fawkes

(Posted 2012) [#4]

Yes. Alls I did was reposition the camera and the objects and gave the player a correct camera :)

Floyd

(Posted 2012) [#5]

What is it that doesn't work? The player moves around, with X and Z changing. When either value reaches +12 or -12 the color changes. Is that not the expected behavior based on

Global G_obb = CreateOBB( 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 12.0, 12.0, 12.0 )

Guy Fawkes

(Posted 2012) [#6]

Well, when u look REAL closely at the player model inside of the cube model that has OBB, does it not look as though the player turns red in areas it should NOT turn red?

Ross C

(Posted 2012) [#7]

.

Last edited 2012

Guy Fawkes

(Posted 2012) [#8]

Ross C

(Posted 2012) [#9]

It works fine:

change the CreateOBB() function to:


Function CreateOBB( x#, y#, z#, pitch#, yaw#, roll#, width#, height#, depth#, parent = 0 )
; Creates an OBB and returns its entity handle. Note that an OBB is just a pivot entity.
; The position, rotation, and size of the OBB will be set using the supplied values. Note that these values are initially applied in global space, but will be relative to the parent space after the obb has been created.
; An optional parent entity can be specified. The obb will be attached to this parent, and its position, rotation, and size will update when the position, rotation, and\or size of the parent changes.

	Local obb_pivot = CreateCube( parent )
	FlipMesh obb_pivot
	PositionEntity obb_pivot, x#, y#, z#, True
	RotateEntity obb_pivot, pitch#, yaw#, roll#, True
	ScaleEntity obb_pivot, width#, height#, depth#, True
	Return obb_pivot
End Function

That will show you a visual representation of what the OBB looks like.

Did you ScaleEntity the G_display_cube:

ScaleMesh G_display_cube, 12.0, 12.0, 12.0

Last edited 2012

Leon Drake

(Posted 2012) [#10]

Guy Fawkes

(Posted 2012) [#11]

yes i did Ross. and leon drake, go bother someone else. i am ignoring ALL idiot ppl in ALL parts of this forum.

Ross C

(Posted 2012) [#12]

Well, that's your problem then. That's not the bounding box, but a representation of it.

Last edited 2012

Guy Fawkes

(Posted 2012) [#13]

i did as u said and replaced the function. its working but only til my object is HALF out of the G_display_cube

Ross C

(Posted 2012) [#14]

It's only a maths check using the centrepoint of the object.

Read the function description:


Function PointInOBB( obb_pivot, x#, y#, z# )
; Tests if the specified x, y, z, point is inside the space of the specified OBB pivot entity.
; If so, a true result is returned. If not, a false result is returned.

If it's a cube, you could test all 8 corners of the cube and if all of them are outside, then turn it red.

Guy Fawkes

(Posted 2012) [#15]

How do I get all 8 corners?

Matty

(Posted 2012) [#16]

To get the corners of a cube there are a number of ways of doing so.

One way would be to loop through the vertices and check against the x/y/z coordinates of each vertex.

Another way would be to use the tformpoint commands in combination with your knowledge of the basic properties of a cube.

Kryzon

(Posted 2012) [#17]

The original function can get the 8 corners. Even though the pivot is scaled in world coordinates, its local scale is always [1.0,1.0,1.0]. Since it compares the 3 axes, it's viewing pivot's scale as a cube and comparing with that.

That's why Stevie G's PointInOBB function compares the position of the point relative to [-1.0, 1.0] values, because locally, for the pivot, that's what its scale is: normalized.

He used the TFormPoint command to transform the XYZ coordinates of the point in question from world-space to zone-space so the comparison is easier to make: the zone (a box-like shape) can have any orientation in world-space the user wants, but when the function looks at it locally, the orientation is always identity\null, with the point in question being the one flying around, potentially inside\outside the zone.

Last edited 2012

Guy Fawkes

(Posted 2012) [#18]

Ok. its still doing that object is half in and half out thing...

Here's the code:

; This lib allows you to create and configure an OBB, and then test if a point or an entity has intruded into the OBB's space.

; An OBB is an Oriented Bounding Box. It is not locked to the dimensional axiis and consequently can be rotated.
; An AABB is an Axially Aligned Bounding Box. It is aligned to the dimensional axiis and consequently cannot be rotated.

; Note that an OBB is really just an AABB that exists in a different coordinate space. To test if a point has intruded into an OBB's space, you transform the point into the OBB's coordinate space and then perform the same box intrusion test that you would use with an AABB.


;_______________________________________________________
; *** EXAMPLE ***



Graphics3D 800, 600, 0, 2
SetBuffer BackBuffer()
HidePointer

Global G_camera = CreateCamera()
CameraRange G_camera,.1,50000
PositionEntity G_camera,0,1,0

AmbientLight 255,255,255

Global G_test_ball = CreateCube()
MoveEntity G_test_ball, 0.0, 0.0, 5.0
PositionEntity G_test_ball,0,1,0

; Create the OBB pivot and set it's transformation data.
Global G_obb = CreateOBB( 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 12.0, 12.0, 12.0 )

; -- Create a cube to display the position of the OBB.
Global G_display_cube = CreateCube( G_obb )
PositionEntity G_display_cube, 0.0, 1.0, 0.0
RotateEntity G_display_cube, 0.0, 0.0, 0.0
ScaleMesh G_display_cube, 12.0, 12.0, 12.0
FlipMesh G_display_cube
EntityAlpha G_display_cube, 0.8
EntityShininess G_display_cube,1
;^^^^^^

sky=CreateCube()
ScaleEntity sky,10000,10000,10000
EntityColor sky,102,102,255
FlipMesh sky

Global land = CreatePlane()
EntityColor land, 0,128,255

Global G_mouse_speed_x#, G_mouse_speed_y#

Local elapsed
Global G_deltatime#
Global G_old_time = MilliSecs()

While Not KeyHit(1)

	Cls
	
	SuperCam(G_camera,G_Test_Ball,.03,8,4,0,0)
	
	py# = EntityY#(G_Test_Ball, True)
	ey# = EntityY#(land, True)
	
	If py#<1.0 Then py# = 1.0
	If py#>2 Then py# = 2

	If ey#<1.0 Then ey# = 1.0
	If ey#>2 Then ey# = 2
	
	PositionEntity G_Test_Ball, EntityX#(G_Test_Ball, True), py#, EntityZ#(G_Test_Ball, True)
	
	MoveEntity G_Test_Ball, 0, (KeyDown(44)-KeyDown(45))*0.002, (KeyDown(17)-KeyDown(31) Or KeyDown(200)-KeyDown(208))*0.002
	
	TurnEntity G_Test_Ball, 0, (KeyDown(30)-KeyDown(32) Or KeyDown(203)-KeyDown(205))*0.05, 0

	; -- Update timing.
	elapsed = MilliSecs() - G_old_time
	If elapsed > 100 Then elapsed = 100
	G_deltatime# = elapsed / 1000.0
	G_old_time = MilliSecs()
	;^^^^^^


	; -- Do the OBB test.
	If PointInOBB( G_obb, EntityX#(G_test_ball, True), EntityY#(G_test_ball, True), EntityZ#(G_test_ball, True))
		EntityColor G_test_ball, 0.0, 255.0, 0.0
	Else
		EntityColor G_test_ball, 200.0, 0.0, 0.0
	EndIf
	;^^^^^^
	
	UpdateWorld
	RenderWorld
	Color 255,255,255
	Text 10, 10, "Press W, A, S, D, F, C keys to move. Press ESCAPE to exit."
	Text 10, 30, "The ball's color will change from red to green when it intrudes into the OBB."
	Text GraphicsWidth()/2, GraphicsHeight()/2, "X: "+EntityX#(G_Test_Ball, True), 1, 1
	Text GraphicsWidth()/2, GraphicsHeight()/2+20, "Y: "+EntityY#(G_Test_Ball, True), 1, 1
	Text GraphicsWidth()/2, GraphicsHeight()/2+40, "Z: "+EntityZ#(G_Test_Ball, True), 1, 1
	Flip 0
Wend

End

Function SuperCam(cam,ent,cspeed#,dist#,hite#,xrot#,tilt#)
	
	TFormPoint 0,hite#,-dist#,ent,0
	
	cx#=(TFormedX()-EntityX(cam))*cspeed#
	cy#=(TFormedY()-EntityY(cam))*cspeed#
	cz#=(TFormedZ()-EntityZ(cam))*cspeed#
	
	TranslateEntity cam,cx,cy,cz
	PointEntity cam,ent
	RotateEntity cam,xrot#,EntityYaw(cam),tilt#
	
End Function

Function CreateOBB( x#, y#, z#, pitch#, yaw#, roll#, width#, height#, depth#, parent = 0 )
; Creates an OBB and returns its entity handle. Note that an OBB is just a pivot entity.
; The position, rotation, and size of the OBB will be set using the supplied values. Note that these values are initially applied in global space, but will be relative to the parent space after the obb has been created.
; An optional parent entity can be specified. The obb will be attached to this parent, and its position, rotation, and size will update when the position, rotation, and\or size of the parent changes.

	Local obb_pivot = CreateCube( parent )
	FlipMesh obb_pivot
	PositionEntity obb_pivot, x#, y#, z#, True
	RotateEntity obb_pivot, pitch#, yaw#, roll#, True
	ScaleEntity obb_pivot, width#, height#, depth#, True
	Return obb_pivot
End Function



Function PointInOBB( obb_pivot, x#, y#, z# )
; Tests if the specified x, y, z, point is inside the space of the specified OBB pivot entity.
; If so, a true result is returned. If not, a false result is returned.

	TFormPoint x#, y#, z#, 0, obb_pivot
	x# = TFormedX() : y# = TFormedY() : z# = TFormedZ()
	If ( x# >= -1.0 ) And ( x# <= 1.0 )
		If ( y# >= -1.0 ) And ( y# <= 1.0 )
			If ( z# >= -1.0 ) And ( z# <= 1.0 )
				Return True
			EndIf
		EndIf
	EndIf
	Return False
End Function



Function EntityInOBB( obb_pivot, entity_to_test )
; Tests if the specified entity to test is inside the space of the specified OBB pivot entity.
; If so, a true result is returned. If not, a false result is returned.

	TFormPoint EntityX#( entity_to_test, True ), EntityY#( entity_to_test, True ), EntityZ#( entity_to_test, True ), 0, obb_pivot
	x# = TFormedX() : y# = TFormedY() : z# = TFormedZ()
	If ( x# >= -1.0 ) And ( x# <= 1.0 )
		If ( y# >= -1.0 ) And ( y# <= 1.0 )
			If ( z# >= -1.0 ) And ( z# <= 1.0 )
				Return True
			EndIf
		EndIf
	EndIf
	Return False
End Function

Ross C

(Posted 2012) [#19]

You need to check the corners of the box. If you know the centre point and the width,height and depth of the box, it's just a case of halving the width depth and height to find the corners of the box. Test each of these points, as I said last time, and if all are inside, then it remains green.

eg

centre_x = 3
centre_y = 3
width# = 1
height# = 1
depth# = 1
corner_1_x = centre_x -(width/2)
corner_1_y = centre_y -(height/2)
corner_1_z = centre_z -(depth/2)

Guy Fawkes

(Posted 2012) [#20]

ok. how do u get the center x and center y?

Ross C

(Posted 2012) [#21]

EntityX()... EntityY()... EntityZ(). If your going by your created cube.