The Wigner function formalism which relates source size parameters to experimental ``HBT radii'' extracted from two-particle Bose--Einstein correlations is generalized to azimuthally deformed and longitudinally tilted sources. It is explained how this can be used to complement anisotropic flow measurements with relevant space-time information on the source.

PACS numbers: 25.75.-q, 25.75.Gz, 25.75.Ld, 24.10.Nz