Directional Lightmap baking script problems

Hi, i've been working on a script to bake directional lightmaps (or Radiosity Normal maps as Valve called it) using 3ds Max but i'm having issues with the lightmaps it produces.

The script modifies the normals of the objects to face the 3 basis vectors before baking the lightmaps, but I think there is something amiss when doing this as the lightmaps aren't producing the required result.

The 3 lightmaps for an unwrapped box end up coming out like this:
 photo Box01_dlm1.jpg
 photo Box01_dlm2.jpg
 photo Box01_dlm3.jpg

And the final lightmap with shader looks like this:
 photo ProblemDLM.jpg

The code that modifies the normals is as follows:

-----------------------------------------------------------------------------------------------------
-- computeTangentSpace function taken from HalfVector on cgsociety
-- The face position has been removed from the resulting matrices
-- http://forums.cgsociety.org/showpost.php?p=3881243&postcount=11
function computeTangentSpace obj =
(
	local theMesh = snapshotAsMesh obj
 
	local tSpace = #()
 
	-- Do we have to flip faces?
	local flip = false
	local indices = #(1, 2, 3)
	if dot (cross obj.transform.row1 obj.transform.row2) obj.transform.row3 <= 0 do (
		indices[2] = 3
		indices[3] = 2
		flip = true
	)
 
	for nFace = 1 to theMesh.numFaces do (
		local face = getFace theMesh nFace
		local tface = getTVFace theMesh nFace
 
		local v1 = getVert theMesh face[indices[1]]
		local v2 = getVert theMesh face[indices[2]]
		local v3 = getVert theMesh face[indices[3]]
 
		local uv1 = getTVert theMesh tface[indices[1]]
		local uv2 = getTVert theMesh tface[indices[2]]
		local uv3 = getTVert theMesh tface[indices[3]]
 
		local dV1 = v1 - v2
		local dV2 = v1 - v3
 
		local dUV1 = uv1 - uv2
		local dUV2 = uv1 - uv3
 
		local area = dUV1.x * dUV2.y - dUV1.y * dUV2.x
		local sign = if area < 0 then -1 else 1
 
		local tangent = [0,0,1]
 
		tangent.x = dV1.x * dUV2.y - dUV1.y * dV2.x
		tangent.y = dV1.y * dUV2.y - dUV1.y * dV2.y
		tangent.z = dV1.z * dUV2.y - dUV1.y * dV2.z
 
		tangent = (normalize tangent) * sign
 
		local normal = normalize (getFaceNormal theMesh nFace)
		if flip do normal = -normal
 
		local binormal = (normalize (cross normal tangent)) * sign
 
		append tSpace (Matrix3 tangent binormal normal [0,0,0])
	)
 
	delete theMesh
 
	return tSpace
)
function SetNormalsModifier nodeList &editNormalsMod lightmapType =
(
	normalBasis = [0, 0, 1]
	if (lightmapType == 1) then
	(
		return 0
	)
	else if (lightmapType == 2) then
	( 
		normalBasis = [sqrt (2.0 / 3.0), 0, 1.0 / (sqrt 3.0)]
	)
	else if (lightmapType == 3) then
	(
		normalBasis = [-(1.0 / (sqrt 6.0)), 1.0f / (sqrt 2.0), 1.0f / (sqrt 3.0)]
	)
	else if (lightmapType == 4) then
	(
		normalBasis = [-(1.0 / (sqrt 6.0)), -(1.0f / (sqrt 2.0)), 1.0f / (sqrt 3.0)]
	)
 
	for j = 1 to nodeList.count do
	(
		obj = nodeList[j]
 
		-- Get the face TBN's
		meshFaceTBNs = computeTangentSpace obj
 
		normalFaceCount = editNormalsMod.getNumFaces node:obj
		normalVertexCount = editNormalsMod.getNumNormals node:obj
 
		-- Create an array of arrays to contain the vertex normals for averaging later
		normalsListArray = #()
 
		for i = 1 to normalVertexCount do
		(
			append normalsListArray #()
		)
 
		for i = 1 to normalFaceCount do
		(
			faceSelectionArray = #{i}
			normalSelection = #{}
 
			-- Get the normal indices of the selected face
			editNormalsMod.ConvertFaceSelection &faceSelectionArray &normalSelection node:obj
 
			-- Get the face TBN
			TBN = meshFaceTBNs[i]		
 
			for k in normalSelection do
			(
				-- Transform the normal basis into tangent space?
				normal = normalize(normalBasis * TBN)
 
				-- Append the new normal to a list for this vertex
				append normalsListArray[k] normal
			)
		)
 
		for i = 1 to normalVertexCount do
		(
			normal = [0, 0, 0]
 
			-- Average the normals from the list for this vertex
			for k = 1 to normalsListArray[i].count do
			(
				normal += normalsListArray[i][k]
			)
 
			normal /= normalsListArray[i].count
 
			-- Set the vertex normal
			editNormalsMod.SetNormal i (normalize normal) node:obj
		)
	)
)

I've also attached the script as-is and a DirectX shader to test with. The script is set up as a macroscript so will need to be added as a button to your UI. The shader requires lightmap coords and normal texture coords in channels 1 and 2, and has a checkbox to state which is which.

I have a feeling there is a matrix transform i'm missing to get the normal bases from Direct3D's coordinate system to 3ds' but nothing i've tried has magically fixed the problem and I don't understand everything here well enough to know the exact reason why it doesn't work.

AttachmentSize
renderlightmaps.zip7.94 KB