Program is break without any prompting

[NoIE]

code:

Script.parentObj = nil--entity

function Script:Start()
   self.center = self.entity:FindChild("center")
   if self.center~= nil then
       local pos = self.center:GetPosition(true)        
       self.jointBall = Joint:Ball(pos.x, pos.y,pos.z,self.entity,self.parentObj)    


    ------------------------------------------------------------------------------------------------------
    -- There are also "self.parentObj:Get...", but it will not cause problems.
       self.length = pos:DistanceToPoint(self.parentObj:GetPosition(true))
    ------------------------------------------------------------------------------------------------------

   end
end

--[[function Script:Collision(entity, position, normal, speed)
   --if speed> 0.01  and entity.script.tag ~= nil and entity.script.tag == "player" then

   --    entity.script:TakeDamage(3)

   --end
end]]--

function Script:UpdatePhysics()
   local pp = self.parentObj:GetPosition(true)
   local cp = self.center:GetPosition(true)
   local d = cp
   local length = d:Length()
   --if length > self.length+0.1 then
   --    local np =  pp + d:Normalize()*self.length - (cp - self.entity:GetPosition(true))
   --    self.entity:SetPosition( (self.entity:GetPosition(true)*3 + np  )/4 , true)
   --end
end

When I commented " local pp = self.parentObj:GetPosition(true)", it can run, otherwise break immediate. It without any warning.

[Rick]

What did you link to parentObj in the editor? If it's csg then it needs a mass or script attached otherwise it won't be treated as a valid entity as it gets collapsed into nothingness (I don't know, I hear it gets collapsed and not sure what that means but I know it means it's not treated as an entity).

[NoIE]

What did you link to parentObj in the editor? If it's csg then it needs a mass or script attached otherwise it won't be treated as a valid entity as it gets collapsed into nothingness (I don't know, I hear it gets collapsed and not sure what that means but I know it means it's not treated as an entity).

 

My program will start running and then close immediately. I think I linked parentObj, Because Start function uses parentObj.

 

I also checked the editor. Just now, I tried to remove the link, and then I find

Script Error

 

 

attempt to index field 'parentObj' (a nil value)

 

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