Shortest rotation path

[Rick]

Just testing something. Imagine you had a top down camera view and you moved the character controller with WASD. No rotation just forward/backward strafe left/right. However, the player avatar isn't the controller. It's separate but it's position is set to the controllers. However if you rotate the model to face the direction the controller is going then if the controller is strafing left the model rotates left, if going forward the model faces forward, etc (includes diagonals).

So I have a check on the move and strafe variables that get passed to SetInput() that determines what the angle is to rotate the model. Values 0 - 315 increasing by 45 degrees. They are hardcoded though. If press 'S' then the angle is 0, if 'W' then the angle is 180, if 'A' then the angle is 90 and if 'D' then the angle is 270. If the current angle is > 180 and you press 'S' key to move it back to 0, it will take the long way around to get back to 0 (I use Math:Curve to smooth the current/target values). So the question is how can I get this rotation so it doesn't take the long way around.

function Script:Start()
	self.window = Window:GetCurrent()
	self.model = Model:Load("Models/Knight/Knight Arthur Mecanim.mdl")
	self.model:SetScale(Vec3(0.01, 0.01, 0.01))

	self.model:SetPosition(self.entity:GetPosition(true), true)

	self.damping = 5
	self.rot = 0
	self.targetRot = 0
	self.pos = self.entity:GetPosition(true)
end

function Script:CalcShortestRot(current, target)
	local dist = target - current + 180
	dist = dist - math.floor(dist / 2 / 180) * 2 * 180 - 180

	if dist < 0 then
		return current - dist
	elseif dist > 0 then
		return current + dist
	else
		return target
	end
end

function Script:UpdateWorld()
	local move = ((window:KeyDown(Key.W) and 1 or 0) - (window:KeyDown(Key.S) and 1 or 0))*4
	local strafe = ((window:KeyDown(Key.D)and 1 or 0) - (window:KeyDown(Key.A) and 1 or 0))*4
	local jump = (window:KeyHit(Key.Space) and 1 or 0)*8

	self.entity:SetInput(0,move,strafe,jump,false)

	-- position the model at the character controllers position
	local pos = self.entity:GetPosition(true)
	self.pos.x = Math:Curve(pos.x, self.pos.x, self.damping)
	self.pos.y = Math:Curve(pos.y, self.pos.y, self.damping)
	self.pos.z = Math:Curve(pos.z, self.pos.z, self.damping)

	self.model:SetPosition(self.pos)

	-- determine the model rotation based on direction we are going
	if move > 0 then
		if strafe > 0 then
			self.targetRot = self:CalcShortestRot(self.targetRot, 225)
			--self.targetRot = 225
		elseif strafe < 0 then
			--self.targetRot = 135
			self.targetRot = self:CalcShortestRot(self.targetRot, 135)
		else
			--self.targetRot = 180
			self.targetRot = self:CalcShortestRot(self.targetRot, 180)
		end
	elseif move < 0 then
		if strafe > 0 then
			--self.targetRot = 315
			self.targetRot = self:CalcShortestRot(self.targetRot, 315)
		elseif strafe < 0 then
			--self.targetRot = 45
			self.targetRot = self:CalcShortestRot(self.targetRot, 45)
		else
			--self.targetRot = 360
			self.targetRot = self:CalcShortestRot(self.targetRot, 360)
		end
	elseif strafe > 0 then
		--self.targetRot = 270
		self.targetRot = self:CalcShortestRot(self.targetRot, 270)
	elseif strafe < 0 then
		--self.targetRot = 90
		self.targetRot = self:CalcShortestRot(self.targetRot, 90)
	end

	self.rot = Math:Curve(self.targetRot, self.rot, self.damping)

	self.model:SetRotation(Vec3(0, self.rot, 0), true)
end

 

[macklebee]

Refer to the LE2 math.lua script which had useful functions to address this.

 

math.lua

 

Granted looking over the wiki, LE4 may already have this code incorporated into Math:DeltaAngle(), Math:CurveAngle(), and Math:IncAngle(). It appears you are trying to re-invent what Josh has already provided to you.

[Rick]

Adding the value Math:DeltaAngle() returned did the trick thanks. For future reference and others who may wish to know:

    -- determine the model rotation based on direction we are going
	if move > 0 then
		if strafe > 0 then
			self.targetRot = self.targetRot + Math:DeltaAngle(self.targetRot, 225)
		elseif strafe < 0 then
			self.targetRot = self.targetRot + Math:DeltaAngle(self.targetRot, 135)
		else
			self.targetRot = self.targetRot + Math:DeltaAngle(self.targetRot, 180)
		end
	elseif move < 0 then
		if strafe > 0 then
			self.targetRot = self.targetRot + Math:DeltaAngle(self.targetRot, 315)
		elseif strafe < 0 then
			self.targetRot = self.targetRot + Math:DeltaAngle(self.targetRot, 45)
		else
			self.targetRot = self.targetRot + Math:DeltaAngle(self.targetRot, 0)
		end
	elseif strafe > 0 then
		self.targetRot = self.targetRot + Math:DeltaAngle(self.targetRot, 270)
	elseif strafe < 0 then
		self.targetRot = self.targetRot + Math:DeltaAngle(self.targetRot, 90)
	end

    self.rot = Math:Curve(self.targetRot, self.rot, self.damping)

	self.model:SetRotation(Vec3(0, self.rot, 0), true)