Making an object always stay on the same position and rotation on the camera (First person objects).

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SmileSlime

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Posted: 1st Nov 2017 04:06

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I want to have my first-person game to show a 3D object that stays in the same position and rotation on the screen. Like a sword that the player holds. I've tried to do this but most of the time the object would rotate too far away from the camera, making it look weird.

I don't really know if I worded this right, but I'd like to know how I can do this.

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Markus

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Posted: 1st Nov 2017 11:45

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i think you can set the same position as the camera, then rotate same as camera, then
RotateObjectLocal & MoveObjectLocal in front of camera

AGK (Steam) V2017.09.25 : Windows 10 Pro 64 Bit : AMD (17.9.3) Radeon R7 265 : Mac mini OS High Sierra (10.13)

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SmileSlime

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Posted: 1st Nov 2017 16:51

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Quote: "i think you can set the same position as the camera, then rotate same as camera, then
RotateObjectLocal & MoveObjectLocal in front of camera"

That doesn't sound that clear to me. I tried what you said but it doesn't seem to work.
I hope someone comes up with an example.

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Jack

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Posted: 1st Nov 2017 17:12 Edited at: 1st Nov 2017 17:22

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This may help you.

+ Code Snippet

// fix an object to the camera code 0.1 (untested)
yourgun = LoadObject("MyGunWithCorrectOrigin.Format")
BestOffsetX# = 0.0
BestOffsetY# = 0.0
BestOffsetZ# = 0.0
setobjectposition(yourgun,BestOffsetX#,BestOffsetY#,BestOffsetZ#) // set it to 0.0 and if you need an offset of your gun, then use the z axis to move
FixObjectPivot( yourgun ) // fixes a new pivot, so no movelocal stuff in the loop
do

cpx# = GetCameraX(1)
cpy# = GetCameraY(1)
cpz# = GetCameraZ(1)

crx# = GetCameraAngleX(1)
cry# = GetCameraAngleY(1)
crz# = GetCameraAngleZ(1)

.... your loop code

setobjectposition(yourgun,cpx#,cpy#,cpz#)
setobjectrotation(yourgun,crx#,cry#,crz#)

sync()
loop

I also think, that you need some sort of depth control, so your gun always stays infront of the walls of your level.
Just go though each 3d command in the code reference, the description will tell what they can.
I think setobjectdepth() will be enough for this task.
The next think would be to replace crx#, cry#, crz# with a curveangle function value, so the gun would smoothly rotate with the camera.

The most elegant way would be a shader for the camera fix, as it saves the most ressources and keeps your code clean from visual operations.
But the AppGameKit solution will help you better to understand how it works.

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Markus

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Posted: 1st Nov 2017 17:46

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example from me

rem
rem AGK Application 2017.09.25
rem MR 01.11.2017

rem Landscape App
SetWindowSize(1280,720,0)
SetDisplayAspect( 16.0/9.0 )
SetVirtualResolution(1280,720)

SetSunDirection(0,-.9,.1)
SetSunColor(255,255,255)

setcameraposition(1,0,1.80,0)
SetCameraLookAt(1,0,1.0,10,0)
SetCameraFOV(1, 80 )
SetCameraRange(1,0.1,1000.0)

Main()
End

Function Main()

ground=CreateObjectPlane(1000,1000) //XY
	SetObjectLightMode(ground,1)
	RotateObjectGlobalX(ground,90)
	SetObjectColor(ground,100,120,50,255)

human = CreateObjectCylinder(1.8,.4,8)
	SetObjectColor(human,255,192,192,255)
	SetObjectLightMode(human,1)
	SetObjectPosition(human,0,.6,0)

sword = CreateObjectCylinder(1,.1,8)
	SetObjectColor(sword,192,192,192,255)
	SetObjectLightMode(sword,1)

RandomCubes()

local a as float

rem A Wizard Did It!
	do
	 Print("hello 3d sword , esc to exit")

RotateObjectGlobalY(human,-10.0/60.0)

HumanForward(human,1.0/60.0)
	 Sword(human,sword,sin(a)*60.0)
	 CameraBehind(human)

a = a + 45.0 / 60.0
	 if a > 360.0 then a = a -360.0
	
	 if GetRawKeyPressed ( 27 ) then exit 
		
	 Sync()
	loop
	
EndFunction

Function RandomCubes()

for i = 1 to 1000 
	o=CreateObjectBox(.5,.5,.5)
	SetObjectPosition(o,Random2(-100,100),0.25,Random2(-100,100))
	SetObjectLightMode(o,1)
	SetObjectColor(o,Random2(20,255),Random2(20,255),Random2(20,255),255)
 next
	
EndFunction

Function CameraBehind(human)

local x as float,y as float,z as float
	
	x=getobjectx(human)
	y=getobjecty(human)
	z=getobjectz(human)
	
	setcameraposition(1,x,y,z)
	
	x=GetObjectAngleX(human)
	y=GetObjectAngleY(human)
	z=GetObjectAngleZ(human)

SetCameraRotation(1,x,y,z)

MoveCameraLocalY(1,.90) //move to head
	MoveCameraLocalZ(1,-1.5) //behind
	
EndFunction

function HumanForward(human as integer,amount as float)
	
	MoveObjectLocalZ(human,amount)
	
endfunction

Function Sword(human,sword,angle)
		
	local x as float,y as float,z as float
	
	x=getobjectx(human)
	y=getobjecty(human)
	z=getobjectz(human)
	
	SetObjectPosition(sword,x,y,z) //same as human
	
	x=GetObjectAngleX(human)
	y=GetObjectAngleY(human)
	z=GetObjectAngleZ(human)

SetObjectRotation(sword,x,y,z) //same as human

RotateObjectLocalY(sword,-20) //turn into front

MoveObjectLocalX(sword,.30) //move right
	MoveObjectLocalY(sword,.9) //move up
	MoveObjectLocalZ(sword,.2) //move forward

RotateObjectLocalX(sword,angle) //swing

EndFunction

+ Code Snippet

rem
rem AGK Application 2017.09.25
rem MR 01.11.2017

rem Landscape App
SetWindowSize(1280,720,0)
SetDisplayAspect( 16.0/9.0 )
SetVirtualResolution(1280,720)

SetSunDirection(0,-.9,.1)
SetSunColor(255,255,255)

setcameraposition(1,0,1.80,0)
SetCameraLookAt(1,0,1.0,10,0)
SetCameraFOV(1, 80 )
SetCameraRange(1,0.1,1000.0)

Main()
End

Function Main()

	ground=CreateObjectPlane(1000,1000) //XY
	SetObjectLightMode(ground,1)
	RotateObjectGlobalX(ground,90)
	SetObjectColor(ground,100,120,50,255)

	human = CreateObjectCylinder(1.8,.4,8)
	SetObjectColor(human,255,192,192,255)
	SetObjectLightMode(human,1)
	SetObjectPosition(human,0,.6,0)

	sword = CreateObjectCylinder(1,.1,8)
	SetObjectColor(sword,192,192,192,255)
	SetObjectLightMode(sword,1)

	RandomCubes()

	local a as float

	rem A Wizard Did It!
	do
	 Print("hello 3d sword , esc to exit")

	 RotateObjectGlobalY(human,-10.0/60.0)

	 HumanForward(human,1.0/60.0)
	 Sword(human,sword,sin(a)*60.0)
	 CameraBehind(human)

	 a = a + 45.0 / 60.0
	 if a > 360.0 then a = a -360.0
	
	 if GetRawKeyPressed ( 27 ) then exit 
		
	 Sync()
	loop
	
EndFunction 

Function RandomCubes()

 for i = 1 to 1000 
	o=CreateObjectBox(.5,.5,.5)
	SetObjectPosition(o,Random2(-100,100),0.25,Random2(-100,100))
	SetObjectLightMode(o,1)
	SetObjectColor(o,Random2(20,255),Random2(20,255),Random2(20,255),255)
 next
	
EndFunction 

Function CameraBehind(human)

	local x as float,y as float,z as float
	
	x=getobjectx(human)
	y=getobjecty(human)
	z=getobjectz(human)
	
	setcameraposition(1,x,y,z)
	
	x=GetObjectAngleX(human)
	y=GetObjectAngleY(human)
	z=GetObjectAngleZ(human)

	SetCameraRotation(1,x,y,z)

	MoveCameraLocalY(1,.90) //move to head
	MoveCameraLocalZ(1,-1.5) //behind
	
EndFunction 

function HumanForward(human as integer,amount as float)
	
	MoveObjectLocalZ(human,amount)
	
endfunction

Function Sword(human,sword,angle)
		
	local x as float,y as float,z as float
	
	x=getobjectx(human)
	y=getobjecty(human)
	z=getobjectz(human)
	
	SetObjectPosition(sword,x,y,z) //same as human
	
	x=GetObjectAngleX(human)
	y=GetObjectAngleY(human)
	z=GetObjectAngleZ(human)

	SetObjectRotation(sword,x,y,z) //same as human

	RotateObjectLocalY(sword,-20) //turn into front

	MoveObjectLocalX(sword,.30) //move right
	MoveObjectLocalY(sword,.9) //move up
	MoveObjectLocalZ(sword,.2) //move forward

	RotateObjectLocalX(sword,angle) //swing

EndFunction

AGK (Steam) V2017.09.25 : Windows 10 Pro 64 Bit : AMD (17.9.3) Radeon R7 265 : Mac mini OS High Sierra (10.13)

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SmileSlime

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Joined: 10th May 2017

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Posted: 1st Nov 2017 19:32

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Quote: "This may help you."

Quote: "example from me"

Thank you both, I will try to integrate these into my projects.

I love games, who doesn't?

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AppGameKit Classic Chat / Making an object always stay on the same position and rotation on the camera (First person objects).