Game object not showing (SOLVED)

Questions
1

I’m trying to move a game object (with a sprite) using the following code:

go.property("speed", 5)

function init(self)
	msg.post(".", "acquire_input_focus")
	self.velocity = vmath.vector3()
end

function update(self, dt)
	self.velocity = vmath.normalize(self.velocity)
	local position = go.get_position()
	print(position)
	position = position + self.velocity * self.speed * dt
	go.set_position(position)
	self.velocity = vmath.vector3()
end

function on_input(self, action_id, action)
	if action_id == hash("up") then
		self.velocity.y = 1
	end
	if action_id == hash("down") then
		self.velocity.y = -1
	end
	if action_id == hash("left") then
		self.velocity.x = -1
	end
	if action_id == hash("right") then
		self.velocity.x = 1
	end
end

However, when I add this script component to the game object. The sprite is no longer visible.
I tried to print the position value (as shown here) but it prints a vector with nil values.
I cannot manage th find my error. Any help?

2

Can we normalize a zero vector? Maybe that’s the error?

3

OK. I added this and now the sprite is showing correctly:

	if vmath.length_sqr(self.velocity) > 1 then
		self.velocity = vmath.normalize(self.velocity)
	end

however, my game object still doesn’t move upon input.

4

Well, in fact, the object is moving. It’s just that the speed value is too low to really notice it.
Guess the rubber duck technique really works.^^

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5

Normalizing a vector involves taking the square root of the length of the vector. And if the length of the vector is 0, you get a division by zero, which will cause a NaN.

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6

Yes. I realized this a few seconds after posting. :smile:
A zero length vector cannot become a unit length vector since it doesn’t even have a direction to begin with. :slight_smile:
Thanks!

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