You're not even describing pixel shaders. Vertex normals are what prevents two faces having a seam between them and of course Blitz supports them. Normal mapping is also not required, though it is possible with Blitz, setting the smoothing groups or vertex normals within your modelling program and then exporting to b3d will ensure that there are no seams where there should not be ( and conversely that there are seams where you want seams. )