  We consider different approaches to simulate a modern X-ray beamline. Several
methodologies with increasing complexity are applied to discuss the relevant
parameters that quantify the beamline performance. Parameters such as flux,
dimensions and intensity distribution of the focused beam and coherence
properties are obtained from simple analytical calculations to sophisticated
computer simulations using ray-tracing and wave optics techniques. A
latest-generation X-ray nanofocusing beamline for coherent applications (ID16A
at the ESRF) has been chosen to study in detail the issues related to highly
demagnifying synchrotron sources and exploiting the beam coherence. The
performance of the beamline is studied for two storage rings: the old ESRF-1
(emittance 4000~pm) and the new ESRF-EBS (emittance 150~pm). In addition to
traditional results in terms of flux and beam sizes, an innovative study on the
partial coherence properties based on the propagation of coherent modes is
presented. The different algorithms and methodologies are implemented in the
software suite OASYS. Those are discussed with emphasis placed upon the their
benefits and limitations of each.
