You need to make each side of your cube a separate (unwelded) quad, and then set the normals manually using the VertexNormal command. You can't simply use UpdateNormals as this will smooth them.
How to create lightable box?
Blitz3D Forums/Blitz3D Programming/How to create lightable box?The forum is locked. These are the original blitzbasic.com forums, kept so they can still be read. No new topics, replies or edits can be made here. To join in, head over to the Blitz3D+ forums.