body box vs createcube set scale

[Rick]

Why does the below code produce a larger physics box than cube mesh?

 

object.cube = CreateCube()
object.cube:SetScale(Vec3(2,2,2))				-- default size
object.body = CreateBodyBox(2,2,2)

[Canardia]

It should be the same size.

EDIT: And I verified that it is, by adding those 3 lines to the windmill script (replace object with entity).

The only explanation to your phenomena I can imagine is that you see only half of the mesh, since the lower half is under the terrain, since you created the mesh at 0/0/0.

[Rick]

No, the cube is in the middle of the body box for me so that's not it.

 

This is what it looks like for me.

http://dl.dropbox.com/u/1293842/img.jpg

[Rick]

Can you try it in your editor. Drop this folder anywhere in your leadwerks folder.

 

http://dl.dropbox.com/u/1293842/Pi-Cube.zip

[Canardia]

It seems to me that :SetScale is doing ScaleEntity, which is usually the wrong thing to do. Lua seems to be missing ScaleMesh, which would do it right. As a workaround you can just do:

object.body = CreateBodyBox(1,1,1)

[Rick]

The size will need to be variable though. You'll be able to size it to whatever you want from properties.

 

I thought you said it worked for you with those 3 lines of code, but now you seem to be saying it's not?

[Canardia]

Yes, it works when you add those 3 lines to windmill, without all the other stuff you have, ESPECIALLY without parenting.

[Rick]

lol, well the parenting is kind of key

 

I see now that if I comment out the parenting it's the right size, but I have to have the parenting, so like you said ScaleMesh would probably do it.

 

Although looking at the wiki, it uses ScaleEntity() and parenting just like I'm doing:

 

http://www.leadwerks.com/wiki/index.php?title=CreateBodyBox

[macklebee]

object.body:SetParent(object.cube,1)

[Rick]

Thank macklebee, that did it! I wonder why the wiki tutorial doesn't do that and it works there?

[Rick]

The issue I have now, is when I set the bodymass to 1, the body falls, but the cube doesn't go with it. Any ideas?

 

require("scripts/class")
require("Scripts/hooks")
require("Scripts/linkedlist")


local class=CreateClass(...)


function class:InitDialog(grid)
self.super:InitDialog(grid)

group = grid:AddGroup("Cube")
group:AddProperty("size", PROPERTY_VEC3, "0", "Cube Scale")
group:AddProperty("mat", PROPERTY_FILE, "", "Material")
group:AddProperty("body_mass", PROPERTY_FLOAT, "", "Body Mass")
group:AddProperty("entity_type", PROPERTY_INTEGER, "", "Entity Type")
group:Expand(1)
end

function class:CreateObject(model)
local object=self.super:CreateObject(model)


function object:CreateCube(size, mass, type)
	-- delete if already exists
	if object.cube ~= nil then
		object.cube:Free()
		object.cube = nil
		object.body:Free()
		object.body = nil
	end

	-- create
	object.body = CreateBodyBox(size.x, size.y, size.z)
	object.body:SetMass(mass)
	EntityType(object.body, type)
	object.cube = CreateCube()
	object.cube:SetScale(size)

	object.body:SetParent(object.cube, 1)

	-- paint
	object.mat = LoadMaterial(object.matFile)
	object.cube:Paint(object.mat)

	-- position
	local scale = object.cube:GetScale()
	local pos = object.model:GetPosition()
	pos.y = pos.y - (scale.y / 2)
	object.cube:SetPosition(pos)
	object.cube:SetRotation(object.model:GetRotation())
end

-- defaults
object.model = model
object.matFile = "abstract::cobblestones.mat"
object.bodyMass = 1
object.entityType = 1
object.size = Vec3(2, 2, 2)
object.cube = nil
object.body = nil
object.material = nil

-- create default cube
object:CreateCube(object.size, object.bodyMass, object.entityType)

function object:SetKey(key,value)
	if key == "mat" then
		object.matFile = "abstract::"..value
		object.mat = LoadMaterial(object.matFile)
		object.cube:Paint(object.mat)
	elseif key == "size" then
		object.size = StringToVec3(value)
		object:CreateCube(object.size, object.bodyMass, object.entityType)
	elseif key == "body_mass" then
		object.bodyMass = tonumber(value)
		object:CreateCube(object.size, object.bodyMass, object.entityType)
	elseif key == "entity_type" then
		object.entityType = tonumber(value)
		object:CreateCube(object.size, object.bodyMass, object.entityType)
	else
		return self.super:SetKey(key,value)
	end
	return 1
end

function object:GetKey(key,value)
	if key=="" then
	else
		return self.super:GetKey(key,value)
	end
	return value
end

function object:Update()
	if GetGlobalString("mode") == "GAME_MODE" then
	else	-- editor mode
		-- moves the editor model to the top of the cube
		local scale = object.cube:GetScale()
		local pos = object.model:GetPosition()
		pos.y = pos.y - (scale.y / 2)
		--object.cube:SetPosition(pos)
		--object.body:SetPosition(pos)
		--object.cube:SetRotation(object.model:GetRotation())
	end
end
function object:Free(model)
	if object.cube ~= nil then
		object.cube:Free()
		object.cube = nil
	end
	if object.body ~= nil then
		object.body:Free()
		object.body = nil
	end
	--if object.mat ~= nil then
	--	object.mat:Free()
	--end
	self.super:Free()
end

end

[Niosop]

Parent it the other way and just set the body scale and not the model scale.

[Rick]

Parenting the other way works, except the box and the cube aren't together (the physics body moves with my editor object but the box is created at the origin, however when I move the physics body the box does move also), but from my understanding you can't scale bodies after they are created. You can, but the physics gets messed up from what I remember. That shouldn't be an issue though as I just recreate the physics body when the size changes anyway. Just need to get the cube at the same position as the body now.

 

[EDIT]

I got it. Thank you!

[Rick]

Here's something interesting. So I uncomment the code in the update method that positions the body so I can move the body around in the editor. When I run the game everything drops and works as expected except for 1 detail. The longer I'm in editor mode and then switch to game mode, the faster the objects drop to the ground. For example, if I sit in editor mode for 1 second, then switch to game mode, the objects fall at a decent speed. Then if I go back to editor mode and wait 10 seconds and then go back into game mode, the objects fly to the ground really fast. It's almost because I SetPosition() of the body in editor mode that it's really building up speed behind the scenes, and when I don't call SetPosition() anymore, it still has the speed at which it would be falling. How can I get around this? Ideally I would think that once SetPosition() is called it resets any velocity the body would have so when it's not called on the body anymore the velocity is starting from scratch.

[Rick]

Has anyone experienced issues when setting the position of a physics body and then not setting the position and letting physics happen on the body, but the body velocity is really fast now. Almost like while set position was being called on it, it was increases it's velocity even though it was standing still?

[Canardia]

This fast movement happens when you don't call fw.Update() in each frame. It then tries to catch up the lost time when you next time call fw.Update().

[Rick]

I can't think of a reason why fw.Update() isn't being called. Nothing is blocking it from being called.

[Canardia]

If you do SetPosition on a physics body in each frame, then it might also do the same, as a missing fw.Update().

You should use AddBodyForce with CalcBodyVelocity to simulate SetPosition on physics bodies.

[Rick]

hmm, well this is all just for editor mode so you can position the cube where you want it to be when the game runs. I need the cube to follow the position of the editor object model. Would you think there would be a way to reset the physics body so it doesn't have this high velocity after SetPosition() is stopped being called on the body? That way I could do that on the first run inside the update method.

[Rick]

I found a work around. I set the mass to 0 when in editor mode, and the first time in Update in game mode is where I set the mass to whatever the user sets in the properties. That seems to work out well.