# 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:

And the final lightmap with shader looks like this:

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.

Attachment | Size |
---|---|

renderlightmaps.zip | 7.94 KB |