The Ultimate Guide to Vector3:Cross() and Vector3:Dot()

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#12

Yeah ofc, just use:

local vectorA = Vector3.new(0, 1, 0)
local vectorB = Vector3.new(0, 0, -1)
local yourVectorC = vectorA:Lerp(vectorB, 0.5).Unit * vectorA.Magnitude
print(yourVectorC)
4 Likes
#13

Finally, a good tutorial explaining :Cross() and :Dot(), really good guide :+1: (also your rocket building skills are 10x better than mine)

3 Likes
#14

preciate that bro! :joy:

charactacter30

2 Likes
#15

I give you a whopping 1000/10 of your explanation

4 Likes
#16

Uh @Moonvane , what if their angle are 45, will it be -0.5

3 Likes
#17

Yes it will be 0.5 if the angles are 45 from each other and -0.5 if the angles are 135 degrees from eachother (135 is just the flipped version of 45)

2 Likes
#18

I made a car, and I would like to detect next waypoints, the car moves by waypoints, if the next way point is to the right side of car, car should turn right

How do I detect if the waypoint is right side of the car

1 Like
#19

Ok this actually doesn’t even need to use Dot, what you can do is just number the waypoints in order and then tween the car to the next waypoint.

1 Like
#20

No like, the car moves through tween, but the thing is, the steering inside the car should also move like auto pilot, so I need to detect left or right the car moves in order to find which side its going

How do I do it?

1 Like
#21

You can use dot product to find the angle, and cross product to find the direction left or right.

Ex from Sleitnick is AngleBetween signed:

local function AngleBetween(vectorA, vectorB)
	return math.acos(math.clamp(vectorA:Dot(vectorB), -1, 1))
end

local function AngleBetweenSigned(vectorA, vectorB, axis)
	local unsigned = AngleBetween(vectorA, vectorB)
	local cross = vectorA:Cross(vectorB)
	local sign = math.sign((axis.X * cross.X) + (axis.Y * cross.Y) + (axis.Z * cross.Z))
	return (unsigned * sign)
end
4 Likes
#22

It does not work either it gets the correct angle

2 Likes
#23

Well that is the simplest explanation of cross and dot I have ever seen. Incredible.
Great job, best tutorial on the devforum by far.

1 Like
#24

I appreciate it dude!!
This is enough chrar

1 Like
#25

I really used to think these are complicated and for crazy good scripters who know what they are doing but turns out its simple as heck ty man have a great life!

1 Like
#26

hi i was wondering if you knew how to find if the player is going down a slope, I need it to make the player go faster when they are sliding down a slope. this is what I have but what would go in the NORMAL part of the script

local incline = Vector3.new(1, 0, 0):Cross(Vector3.new(NORMAL)

				if incline.magnitude == 0 then
					incline = Vector3.new(1, 0, 0)
				end

				local angle = math.acos(Vector3.new(0, 1, 0):Dot(incline))
				if angle > math.pi / 1.5 then
					print("Angle")
					Slide.Velocity = angle * Slide.Velocity * 1.15
				else
					print("No Angle")
					Slide.Velocity = Slide.Velocity * 0.99
				end
1 Like
#27

Ok so this is a perfect example of somewhere where you can utilize Dot, and I love the way you did it in your code. Personally, I would just use a raycast from your HumanoidRootPart directly downward and then just use the normal from that.
(
local ray = workspace:Raycast(HRP.Position, Vector3.new(0, -hipheight - 1, 0), params)
local normal = ray and ray.Normal
)

1 Like
#28

thank you so much i will try that

#29

Its not working but im pretty sure this is my fault, as I’m very new to raycasting I think my variables are off.

local HumanoidRootPart = Character.PrimaryPart
local HipHeight = Humanoid.HipHeight
local Params = RaycastParams.new()
local ray = workspace:Raycast(HumanoidRootPart.Position, Vector3.new(0, -HipHeight - 1, 0), Params)
local normal = ray and ray.Normal

				local incline = Vector3.new(1, 0, 0):Cross(Vector3.new(normal))

				if incline.magnitude == 0 then
					incline = Vector3.new(1, 0, 0)
				end

				local angle = math.acos(Vector3.new(0, 1, 0):Dot(incline))
				if angle > math.pi / 1.5 then
					print("Angle")
					Slide.Velocity = angle * Slide.Velocity * 1.15
				else
					print("No Angle")
					Slide.Velocity = Slide.Velocity * 0.95
				end
1 Like
#30

Ok yes do for the raycast, you will want to include an ignorelist. Do it like this:

local params = RaycastParams.new()
params.FilterDescendantsInstances = {player.Character}
params.FilterType = Enum.RaycastFilterType.Blacklist

#31

ok thanks im trying it out now