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Trouble finding a random point on the top surface of a brick?

Asked by
Trainsparency 39
6 years ago

So what i'm trying to create is a function that spits out a random point on the top surface of a brick, regardless of the brick's rotation, position, or size, which is why I am using directions perpendicular to the faces (lookVector, rightVector, etc)

However, my problem with it is that when the brick is rotated 90* of -90*, the random point always becomes the center of the face.

I'm probably doing something stupid, but here's my code:

function getRandomPointOnTopSurface(Part)

    local Point = nil

    if Part.Shape == Enum.PartType.Block then
        local minLook = Part.CFrame - (Part.CFrame.lookVector * Part.Size.Z/2)
        local maxLook = Part.CFrame + (Part.CFrame.lookVector * Part.Size.Z/2)
        local minRight = Part.CFrame - (Part.CFrame.rightVector * Part.Size.X/2)
        local maxRight = Part.CFrame + (Part.CFrame.rightVector * Part.Size.X/2)

        if minLook.z > maxLook.z then -- switches values so the min isn't greater than the max in math.random()
            maxLook = (-Part.CFrame.lookVector * Part.Size.Z/2)
            minLook = (Part.CFrame.lookVector * Part.Size.Z/2)
        end
        if minRight.x > maxRight.x then
            maxRight = Part.CFrame + (-Part.CFrame.rightVector * Part.Size.X/2)
            minRight = Part.CFrame + (Part.CFrame.rightVector * Part.Size.X/2)
        end


        Point = Vector3.new(math.random(minRight.x, maxRight.x), (Part.CFrame + (Part.CFrame.upVector * Part.Size.Y/2)).y, math.random(minLook.z, maxLook.z))
        print(Point)
    end

    return Point
end

getRandomPointOnTopSurface(workspace.Grass)

Please note I'm not asking for anyone to completely redo my code; I just want to know the flaw with the function -- I can fix it from there

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Answered by
Trainsparency 39
6 years ago
Edited 6 years ago

Nevermind, i found a solution, and apparently its a lot shorter than i imagined! I'll leave the code here --

Edit: It also works with weddges!


function getRandomPoint(Part)

    local Point = nil

    if Part:IsA("Part") then
        Point = Part.Position - (Part.CFrame.lookVector * Part.Size.Z/2) - (Part.CFrame.rightVector * Part.Size.X/2)

        local howfarlook = math.random(0, Part.Size.Z)
        local howfarright = math.random(0, Part.Size.X)

        Point = Point + (Part.CFrame.lookVector * howfarlook) + (Part.CFrame.rightVector * howfarright) + (Part.CFrame.upVector * Part.Size.Y/2)

    elseif Part:IsA("WedgePart") then
        Point = Part.Position - (Part.CFrame.lookVector * Part.Size.Z/2) - (Part.CFrame.rightVector * Part.Size.X/2)

        local howfarlook = math.random(0, Part.Size.Z)
        local howfarright = math.random(0, Part.Size.X)

        local hypot = math.sqrt(Part.Size.Z^2 + Part.Size.Y^2) -- Length of hypotenuse

        local newslantlength = hypot / (Part.Size.Z/howfarlook) -- Length of hypotenuse covering same (relative) z-distance as the selected point
        local subtractY = math.sqrt(newslantlength^2 - howfarlook^2) -- Amount needed to subtract from (relative) y-height to put it on the hypotenuse

        Point = Point + (Part.CFrame.lookVector * howfarlook) + (Part.CFrame.rightVector * howfarright) + (Part.CFrame.upVector * (Part.Size.Y/2 - subtractY))

        print(Point)
    else
        error("Attmpted to generate point on unsupported part: "..Part.Name)
    end

    return Point
end
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