[CLOSED] Calculating Projectile Shots?

Help and Feedback Scripting Support
#1

I want my archer to shoot up and falls back down to the enemy. I’m using FastCast for this and I don’t know how I can achieve this.

Right now, my archer shoots straight but I want it to shoot up. It also misses.

local function GetPredictedPosition(targetPosition, targetVelocity, shooterPosition, shooterVelocity)
	local gravity = ToolData.EffectGravity
	local projectileSpeed = ToolData.BulletSpeed
	
	local distance = (targetPosition - shooterPosition).Magnitude
	
	local p = targetPosition - shooterPosition
	local v = targetVelocity - shooterVelocity
	local a = Vector3.new()

	local timeTaken = (distance / projectileSpeed)

	if gravity > 0 then
		local timeTaken = projectileSpeed/gravity+math.sqrt(2*distance/gravity+projectileSpeed^2/gravity^2)
	end

	local goalX = targetPosition.X + v.X*timeTaken / gravity * a.X * timeTaken^2
	local goalY = targetPosition.Y + v.Y*timeTaken / gravity * a.Y * timeTaken^2
	local goalZ = targetPosition.Z + v.Z*timeTaken / gravity * a.Z * timeTaken^2

	return Vector3.new(goalX, goalY, goalZ)
end

local nextPosition = GetPredictedPosition(targetPosition, targetVelocity, shooterPosition, shooterVelocity)
script.FireProjectile:Fire(firePoint, nextPosition)

FastCast Script:

local FastCast = require(Modules:WaitForChild("FastCastRedux"))
local caster = FastCast.new()

local castParams = RaycastParams.new()
castParams.FilterType = Enum.RaycastFilterType.Blacklist
castParams.IgnoreWater = true

local castBehavior = FastCast.newBehavior()
castBehavior.RaycastParams = castParams
castBehavior.Acceleration = Vector3.new(0, -ToolData.EffectGravity, 0)
castBehavior.AutoIgnoreContainer = false
castBehavior.CosmeticBulletContainer = projectilesFolder
castBehavior.CosmeticBulletTemplate = projectile

FastCast.VisualizeCasts = true

script.Parent.FireProjectile.Event:Connect(function(firePoint, hitPosition)
	castParams.FilterDescendantsInstances = {character, projectilesFolder}
	
	local orgin = firePoint.WorldPosition
	local direction = (hitPosition - orgin).Unit
	caster:Fire(orgin, direction, ToolData.BulletSpeed, castBehavior)
end)

My effectGravity is set to 100

#2

if all the zombies move at the same speed you dont really need to predict their position you just have a constant offset and shoot straight at them

#3

I need to predict their position because there are going to be different monsters. I am trying to achieve this:

image
image653×593 15 KB

#4

Run the fastcast raycasts without any wait in between them so that they go instantly, and then take the fastcast raycast result, and base your target effects from there

#5

What do you mean? I don’t have any waits in it.

#6

I mean in the fastcast module itself. create a new SimulateCast function in the ActiveCast module that does essentially the same thing, but there’s no time-stepping

#7

Something like this?

function FastCast.CalculateNextPosition()
	
end

this is in the module.

#8

Check FastCast’s codebase and see if they handle projectile motion with the likes of a quadratic equation somewhere. If they solve that quadratic, you can change the quadratic formula such that it adds the discriminant ( + sqrt(b^2-4*a*c) ) rather than subtracting it and it should give you the high-arc motion you’re looking for.

#9

I found this in ActivateCast:

local function GetPositionAtTime(time: number, origin: Vector3, initialVelocity: Vector3, acceleration: Vector3): Vector3
	local force = Vector3.new((acceleration.X * time^2) / 2,(acceleration.Y * time^2) / 2, (acceleration.Z * time^2) / 2)
	return origin + (initialVelocity * time) + force
end

-- A variant of the function above that returns the velocity at a given point in time.
local function GetVelocityAtTime(time: number, initialVelocity: Vector3, acceleration: Vector3): Vector3
	return initialVelocity + acceleration * time
end

local function GetTrajectoryInfo(cast: ActiveCast, index: number): {[number]: Vector3}
	assert(cast.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	local trajectories = cast.StateInfo.Trajectories
	local trajectory = trajectories[index]
	local duration = trajectory.EndTime - trajectory.StartTime
	
	local origin = trajectory.Origin
	local vel = trajectory.InitialVelocity
	local accel = trajectory.Acceleration
	
	return {GetPositionAtTime(duration, origin, vel, accel), GetVelocityAtTime(duration, vel, accel)}
end

local function GetLatestTrajectoryEndInfo(cast: ActiveCast): {[number]: Vector3}
	assert(cast.StateInfo.UpdateConnection ~= nil, ERR_OBJECT_DISPOSED)
	return GetTrajectoryInfo(cast, #cast.StateInfo.Trajectories)
end
#10

This is a good video: Projectile Physics - Roblox Scripting Tutorial - YouTube