NUBIGON can calculate normal vectors for your point clouds while opening them. But if your ASCII file (XYZ, PTS, TXT) already contains normal vectors, NUBIGON can also read this information.
Step 1: File > Open point cloud(s) and specify normal channels
When opening point clouds with normal vectors, specify the channels containing the normal information in the ASCII file dialogue.
Step 2: Configure octree generation settings
Uncheck Compute normals in the Octree Generation Settings dialogue to avoid an override and press OK to generate the octree.