throwing something in a arche patern

It is typically done by using a rigid body dynamics simulation with either a physics engine, or possibly just a simplification of those equations.

The arch trajectory is incredibly simple to programm (*), but things get MUCH more complicated when you want the grenade to properly collide with other static or even moving objects in your scene and bounce on contact. Then you really need some kind of physics engine (albeit a very simple one).

[size=2](*) All you need is your initial velocity vector v (magnitude = how strongly you throw; orientation = which direction and under what angle you throw), initial position vector p (the grenade position in the player's hand) and a constant gravity acceleration vector g. Then each frame you just update the velocity and position vectors:
v += g * dt
p += v * dt
where dt is the time span between frames and the operations are vector operations.

(*) All you need is your initial velocity vector v (magnitude = how strongly you throw; orientation = which direction and under what angle you throw), initial position vector p (the grenade position in the player's hand) and a constant gravity acceleration vector g. Then each frame you just update the velocity and position vectors:
v += g * dt
p += v * dt
where dt is the time span between frames and the operations are vector operations.

[s]Gravity only affects the vertical component of velocity.[/s] Haha sorry my bad, I thought you defined g as a scalar. I must be tired - mods feel free to delete this post.