[NEED HELP] Shooting Projectiles in a certain direction

[mdgunn]

I would like to shoot a projectile towards a point in space (in a 2D game). I have something almost working but I can't get my head round how to fix it.

 

I would like to solve the following:

1) How to shoot in a certain direction not just where the mouse is (I could only get it working right with this mouse pointer method but in reality I just want to shoot something in a direction (and maybe not use mouse).

 

2) The projectiles shoot out sort of 90 degrees to where the mouse pointer is but I want them to shoot at where mouse pointer is. I seem to get automatically very confused when thinking about angles.

 

3) At certain positions (90 degrees?) the projectiles sort of flip to the other side when I really just want it to track smoothly all the way round.

 

Here is the code. Can anyone help? Maybe there is just a better way to do it?

 

function App:Start()
 --Create a window
 self.window = Window:Create()
 self.context = Context:Create(self.window)
 self.world = World:Create()
 local camera = Camera:Create()
 camera:SetRotation(35,0,0)
 camera:Move(0,0,-6)
 local light = DirectionalLight:Create()
 light:SetRotation(35,35,0)	
 --Create a model
 self.model = Model:Box()
 return true
end
function App:Loop()

 if self.window:Closed() or self.window:KeyHit(Key.Escape) then return false end
 --Get the vector between the mouse position and the center of the screen
 local v = self.window:GetMousePosition()
 local dx = v.x - self.context:GetWidth()/2.0
 local dy = self.context:GetHeight()/2.0 - v.y
 v = Vec3(dx,dy,0):Normalize()
 --Align the model to the vector
 self.model:AlignToVector(v,2)
-- Create projectile
 bullet = Model:Sphere()
bullet:SetPosition(5,0,0)
bullet:SetMass(1.0)
-- Align to mouse pointer vector
bullet:AlignToVector(v, 2)
-- Add velocity
bullet:SetVelocity(Vec3(0,10,0), false )
 Time:Update()
 self.world:Update()
 self.world:Render()
 self.context:Sync()
 return true
end

 

Thanks,

 

Michael

[Thirsty Panther]

I'm not good on the maths myself but if you change the bullet velocity line to this.

 

bullet:SetVelocity(Vec3(0,0,10), false)

 

It stops the flipping at 0 and 180 degrees.

[mdgunn]

Fantastic, it worked!

 

I was pretty sure I'd tried randomly swapping round my value into the different parameters already, but you're right switching the value to the last parameter (z?) stopped the weird behaviour.

 

This was pretty fundamental to my game so I can actually go ahead now.

 

Many thanks.

 

Now if only I can find enough time to get it finished/started for the tournament.

 

Thanks very much!

 

Cheers,

 

Michael