code: public static void setIdentityM(float[] sm, int smOffset) {
          for (int i=0 ; i<16 ; i++) {
              sm[smOffset + i] = 0;
          }
          for(int i = 0; i < 16; i += 5) {
              sm[smOffset + i] = 1.0f;
          }
      }
docs: Sets matrix m to the identity matrix.
  @param sm returns the result
  @param smOffset index into sm where the result matrix starts