  We have studied the field-orientational dependence of zero-energy density of
states (FODOS) for a series of systems with different Fermi surface and
superconducting gap structures. Instead of phenomenological Doppler-shift
method, we use an approximate analytical solution of Eilenberger equation
together with self-consistent determination of order parameter and a
variational treatment of vortex lattice. First, we compare zero-energy density
of states (ZEDOS) when a magnetic field is applied in the nodal direction
($\nu_{node}(0)$) and in the antinodal direction ($\nu_{anti}(0)$), by taking
account of the field-angle dependence of order parameter. As a result, we found
that there exists a crossover magnetic field $H^*$ so that $\nu_{anti}(0) >
\nu_{node}(0)$ for $H < H^*$, while $\nu_{node}(0) > \nu_{anti}(0)$ for $H >
H^*$, consistent with our previous analyses. Next, we showed that $H^*$ and the
shape of FODOS are determined by contribution from the small part of Fermi
surface where Fermi velocity is parallel to field-rotational plane. In
particular, we found that $H^*$ is lowered and FODOS has broader minima, when a
superconducting gap has point nodes, in contrast to the result of the
Doppler-shift method. We also studied the effects of in-plane anisotropy of
Fermi surface. We found that in-plane anisotropy of quasi-two dimensional Fermi
surface sometimes becomes larger than the effects of Doppler-shift and can
destroy the Doppler-shift predominant region. In particular, this tendency is
strong in a multi-band system where superconducting coherence lengths are
isotropic. Finally, we addressed the problem of cusp-like singularity in
YNi$_2$B$_2$C and present a possible explanation of this phenomenon.
