3D collision detection - GameCreators Forum

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dbenv9

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Posted: 24th Dec 2019 13:41

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Is there any function that detects me if an object collides with another object? Something like: "getCollision(obj1,obj2)", or something similar.
(In my project I use .obj models and I haven't enabled physics)

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fubarpk

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Posted: 24th Dec 2019 14:59

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the following function checks if an object has collided with another object and returns the object id

//EDITED as I noticed I was using x when y and z calculations were needed 
function checkCollision(objID as integer)

local width# as float
local height# as float
local depth# as float
local x# as float
local y# as float
local z# as float
local start_x# as float
local start_y# as float
local start_z# as float
local end_x# as float
local end_y# as float
local end_z# as float 
local object_Hit as integer

//this checks for colliion between an object with any other object and returns its id
width#=(GetObjectMeshSizeMaxX(objID,1)-GetObjectMeshSizeMinX(objID,1))/2 
height#=(GetObjectMeshSizeMaxY(objID,1)-GetObjectMeshSizeMinY(objID,1))/2 
depth#=(GetObjectMeshSizeMaxZ(objID,1)-GetObjectMeshSizeMinZ(objID,1))/2 
 
x#=getObjectWorldX(objID)
y#=GetObjectWorldY(objID)
z#=getObjectWorldZ(objID)

// calculate the start of the ray cast
start_x# = x#-width#
start_y# = y#+height#
start_z# = z#-depth#

// calculate the end of the ray cast
end_x# = x#+width#   
end_y# = y#-height#
end_z# = z#+depth#
 
// determine which object has been hit
object_Hit = ObjectRayCast(0,start_x#,start_y#,start_z#,end_x#,end_y#,end_z#)
endfunction object_Hit

+ Code Snippet

//EDITED as I noticed I was using x when y and z calculations were needed 
function checkCollision(objID as integer)

local width# as float
local height# as float
local depth# as float
local x# as float
local y# as float
local z# as float
local start_x# as float
local start_y# as float
local start_z# as float
local end_x# as float
local end_y# as float
local end_z# as float 
local object_Hit as integer	

//this checks for colliion between an object with any other object and returns its id
width#=(GetObjectMeshSizeMaxX(objID,1)-GetObjectMeshSizeMinX(objID,1))/2 
height#=(GetObjectMeshSizeMaxY(objID,1)-GetObjectMeshSizeMinY(objID,1))/2 
depth#=(GetObjectMeshSizeMaxZ(objID,1)-GetObjectMeshSizeMinZ(objID,1))/2 
 
x#=getObjectWorldX(objID)
y#=GetObjectWorldY(objID)
z#=getObjectWorldZ(objID)


// calculate the start of the ray cast
start_x# = x#-width#
start_y# = y#+height#
start_z# = z#-depth# 

// calculate the end of the ray cast
end_x# = x#+width#   
end_y# = y#-height#
end_z# = z#+depth#
 
// determine which object has been hit
object_Hit = ObjectRayCast(0,start_x#,start_y#,start_z#,end_x#,end_y#,end_z#)
endfunction object_Hit

if you change this line

+ Code Snippet

object_Hit = ObjectRayCast(0,start_x#,start_y#,start_z#,end_x#,end_y#,end_z#)

to

+ Code Snippet

object_Hit = ObjectRayCast(objectID2,start_x#,start_y#,start_z#,end_x#,end_y#,end_z#)

it checks if objID collides with ObjectID2

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dbenv9

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Posted: 24th Dec 2019 21:50

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Thank you very much for the answer, but in this way the collision is only detected along one line, and not on the whole 3D object. Is there a slightly more precise method?

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fubarpk

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Posted: 24th Dec 2019 22:12 Edited at: 24th Dec 2019 22:40

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

If your program uses physics
https://www.appgamekit.com/documentation/Reference/3DPhysics/GetObject3DPhysicsContactObjectB.htm

which is more accurate

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dbenv9

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Posted: 25th Dec 2019 12:13

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Ok, thanks

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Virtual Nomad

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Posted: 28th Dec 2019 06:56 Edited at: 28th Dec 2019 07:07

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Quote: "Something like: "getCollision(obj1,obj2)""

in case you're not working on a full-blown 3d physics project, there IS an easy way to return whether or not 2 objects are colliding but it does use a few commands from the 3d physics command set:

+ Code Snippet

// set display properties
SetVirtualResolution( 1080, 720 ) // doesn't have to match the window
SetOrientationAllowed( 1, 1, 1, 1 ) // allow both portrait and landscape on mobile devices
SetSyncRate( 30, 0 ) // 30fps instead of 60 to save battery
SetScissor( 0,0,0,0 ) // use the maximum available screen space, no black borders
UseNewDefaultFonts( 1 ) // since version 2.0.22 we can use nicer default fonts

Create3DPhysicsWorld() 

Box1 = CreateObjectBox(32,32,32)
	Create3DPhysicsKinematicBody(Box1)
	
Box2 = CreateObjectBox(32,32,32)
	SetObjectPosition(Box2,35,0,0)
	Create3DPhysicsKinematicBody(Box2)

ThisV3 = CreateVector3()

MoveCameraLocalZ(1,-200)

do
    MoveObjectLocalX(Box1, GetRawKeyState(39)-GetRawKeyState(37) ) `RightKey-LeftKey
	
	If GetObjects3DPhysicsContactPositionVector(Box1,Box2,ThisV3) = 1
		SetObjectColor(Box2,255,0,0,255)
	Else
		SetObjectColor(Box2,255,255,255,255)
	Endif
	
    Step3DPhysicsWorld()
    Sync()
loop

specifically: GetObjects3DPhysicsContactPositionVector()

fubarpk's GetObject3DPhysicsContactObjectB method above is generally more involved, cycling through potentially numerous contacts, extracting object #'s, etc.. it will work the same but if you're looking for getCollision(obj1,obj2) behavior, i'd keep it simple.

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AppGameKit Classic Chat / [SOLVED] 3D collision detection