Determine If A Vector3 Is Co-planar Given Another Vector3 And Normal

Help and Feedback Scripting Support
#1

image
image590×520 112 KB

For my OBJ optimizer, I need a way to determine if a point is co-planar, with the input being a Vector3 point on the plane, a unit Vector3 for the normal, and a point to check if it is co-planar. I want to avoid CFrame math since I don’t want to re-implement CFrames in the language I am using.

#2

Not sure if correct.

function IsCoplanar(origin, normal, point)
    return (point-origin):Dot(normal) == 0
end
5 Likes
#3

Works for me.

Validation code:

function Coplanar(origin, normal, point)
    return (point-origin):Dot(normal) == 0
end

local Normal = Vector3.new(0,0,1)
local Point1 = Vector3.new(0,3,2)
local Point2 = Vector3.new(-2,3,2)
local Point3 = Vector3.new(3,5,2)
local Point4 = Vector3.new(2,4,5)

print("Same point: "..(Coplanar(Point1,Normal,Point1) and "Pass" or "Fail"))
print("Generic point 1: "..(Coplanar(Point1,Normal,Point2) and "Pass" or "Fail"))
print("Generic point 2: "..(Coplanar(Point1,Normal,Point3) and "Pass" or "Fail"))
print("Non co-planar point: "..(not Coplanar(Point1,Normal,Point4) and "Pass" or "Fail"))

Output:

1 Like
#4

I would probably replace the == 0 with math.abs(...) < eps for the more general solution, you don’t have to deal with floating point errors in your test cases because your normal is axis-aligned and all the coordinates are integers here. For the general case == 0 won’t be sufficient.

7 Likes