3ds max select similar polygons from current editable poly polygon selection

selectsimilarpoly.ms

// chatgpt
(
    -- SETTINGS
    local tolerance = 0.001
    local ignoreSize = false

    fn compareFloat a b =
    (
        if a < b then -1
        else if a > b then 1
        else 0
    )

    fn getFaceSignature obj faceIndex ignoreSize =
    (
        local verts = polyOp.getFaceVerts obj faceIndex
        local distances = #()

        -- Get every vertex-to-vertex distance.
        -- This describes the polygon shape regardless of rotation/orientation.
        for i = 1 to (verts.count - 1) do
        (
            local p1 = polyOp.getVert obj verts[i]

            for j = (i + 1) to verts.count do
            (
                local p2 = polyOp.getVert obj verts[j]
                append distances (distance p1 p2)
            )
        )

        qsort distances compareFloat

        -- Normalize if we only care about shape and not actual size.
        if ignoreSize and distances.count > 0 do
        (
            local maxDistance = distances[distances.count]

            if maxDistance > 0.000001 do
            (
                for i = 1 to distances.count do
                    distances[i] /= maxDistance
            )
        )

        #(verts.count, distances)
    )

    fn signaturesMatch sigA sigB tolerance =
    (
        -- Different vertex count = different polygon.
        if sigA[1] != sigB[1] then
            return false

        local a = sigA[2]
        local b = sigB[2]

        if a.count != b.count then
            return false

        local epsilon = tolerance

        if a.count > 0 do
        (
            epsilon = a[a.count] * tolerance

            if epsilon < 0.000001 do
                epsilon = 0.000001
        )

        for i = 1 to a.count do
        (
            if abs(a[i] - b[i]) > epsilon then
                return false
        )

        true
    )

    if selection.count != 1 then
    (
        messageBox "Select one Editable Poly object."
    )
    else
    (
        local obj = selection[1]

        if classOf obj.baseObject != Editable_Poly then
        (
            messageBox "The selected object must be an Editable Poly."
        )
        else
        (
            local selectedFaces = polyOp.getFaceSelection obj

            if selectedFaces.numberSet != 1 then
            (
                messageBox "Select exactly one polygon first."
            )
            else
            (
                local referenceFace = 0

                for f in selectedFaces do
                    referenceFace = f

                local referenceSignature =
                    getFaceSignature obj referenceFace ignoreSize

                local result = #{}
                local faceCount = polyOp.getNumFaces obj

                for f = 1 to faceCount do
                (
                    local sig = getFaceSignature obj f ignoreSize

                    if signaturesMatch referenceSignature sig tolerance do
                        result[f] = true
                )

                polyOp.setFaceSelection obj result

                subObjectLevel = 4
                redrawViews()

                format "Selected % similar polygons.\n" result.numberSet
            )
        )
    )
)