FindPartOnRay only detecting at a short distance

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#1

I am making a gun that will detect if a bullet has hit a player. However, when setting up the ray with length of 20, and printing the object hit while directing the gun at a dummy, it continuously prints nil until the Firer (the part with initial position of bullet when in the gun) is about 0.5 studs away from the dummy.

Script:

-- Take Firer to be a part on the gun with a position that a bullet will start firing from.
while true do
    local FTRay = Ray.new(Firer.CFrame.Position, Firer.CFrame.Position + (Firer.CFrame.UpVector * 20))
    local intPart, intPosition = workspace:FindPartOnRay(FTRay, character, false, true)
    print(intPart)
--Additional Test to visualise ray and see if it actually intersects through the object
-- This test shows the end position of the ray by creating a part
	local Test = Instance.new("Part")
	Test.Name = "RayReach"
	Test.Size = Vector3.new(1,1,1)
	Test.Position = Firer.CFrame.Position + (Firer.CFrame.UpVector * 20)
	Test.Parent = game.Workspace
	Test.Anchored = true
	Test.CanCollide = false
--
    wait(0.5)
end

When I adjusted the length of ray from 20 to 500 (replace above * 20 with * 500), the detection was slightly better and the ray could now detect the object from about a range of 15 studs. What is this discrepancy? Shouldn’t a ray detect parts within its length? Why do I need to adjust the length of ray significantly for the detection to work and only for such a small distance?

Thanks.

#2

Try removing the parentheses so you’re multiplying the unit instead of upvector.

#3

It still doesn’t work. I actually thought that adding the parenthesis previously would solve the problem but the problem is still there with or without parenthesis.

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#4

Oh wait, I forgot pemdas for a second, (Firer.CFrame.Position + Firer.CFrame.UpVector) * 20

Did some research and found out it is a param

#5

Yep, according to Roblox’s Developer Hub Tutorial on How to Make a Laser Gun, including this parameter is to ignore the player’s character when shooting the gun.

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#6

Here is the script in action with ray of length 20 studs. Notice that FindPartOnRay only registers for almost negligible distance away. (I’ve changed Firer to my character’s HumanoidRootPart)

#7

What’s the intended direction of the ray? The direction vector that you supplied to Ray.new() looks a little weird. If the direction supposed to be the direction that the front of the player’s torso is facing, then you should just do this:

Ray.new(Firer.CFrame.Position, Firer.CFrame.LookVector * 20)

Since the LookVector(or UpVector, or RightVector) is a directional unit vector, you should be able to simply take the vector as-is, multiply it by the distance, and put it in the Ray.new function.

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#8

Yep, I had changed it up just now to make it simpler. Now, instead of using a LookVector I do:

Ray.new(Firer.CFrame.Position, (Firer.CFrame * CFrame.new(0,1000,0)).Position)

The problem is still there though, although I am starting to think that it is just the nature of how the ray is built into Roblox. So instead of setting the ray to just a length of 20, I set it to 1000 and now, it can detect parts up to about 20 studs, good enough for me. If there is a solution, I am still open to it though.

#9

The second parameter of the ray is a direction vector, not a final position. In the paintball tutorial, you can get the direction towards your mouse with this snippet of code

local ray = Ray.new(tool.Handle.CFrame.p, (mouse.Hit.p - tool.Handle.CFrame.p).unit * 300)

As you can see, by subtracting the position of the mouse.Hit and the origin of the ray, you get a vector specifying the direction. You can get the unit vector by calling .unit, which returns a vector with magnitude 1. Getting the unit vector is important because, through scalar multiplication (multiplying by 300 in this case), you can get a vector with the exact magnitude you specify.

I think with your previous examples, you just got lucky and a ray given the POSITION you defined happened to be pointed in a way that intersected with the dummy.

#10

I think you are right. The previous code on LookVector was rather weird. Using the test part as above

I would sometimes get the part in front of my gun and at other times when I rearrange the code slightly, the test part spawns at a different position, a little to the right of the dummy which made the ray intersect the dummy to reach the part which prompted me to changed from LookVector to

So I agree with you, I definitely got lucky.
What I am still not sure, however, is why is LookVector * 20 not a direction vector? It is a unit vector that is scaled by 20, which would point in that direction, right?

#11

If you are referring to Aesthetical’s solution, Firer.CFrame.LookVector * 20 is a direction vector constructed the way you wanted. However, you replied to him saying that you used

(Firer.CFrame * CFrame.new(0,1000,0)).Position

instead of the lookvector.

In your sample, you used the UpVector and not the LookVector