s3d_load_line_normals - add normals to line
#include <s3d.h> int s3d_load_line_normals(int object, const float *nbuf, uint32_t start, uint16_t n);
Just as s3d_pep_line_normals(), with the difference you won´t alter the latest n lines but n lines starting with index start.
Simon Wunderlich Author of s3d