SLIC (Simple Line Interface Calculation) is an alternating-direction method for geometrically approximating fluid interfaces in one, two, or three space dimensions. Key features of SLIC include: 1. Fluid surfaces are locally represented for each mixed-fluid zone, defined as a composition of one-dimensional components in each coordinate direction. 2. These one-dimensional components are composed entirely of straight lines, either perpendicular or parallel to the coordinate direction. 3. The one-dimensional surface approximations for a mixed fluid cell are determined by testing the presence or absence of fluids in the adjacent zones. 4. The one-dimensional nature of SLIC simplifies the time advancement of fluid surfaces, making it practical for numerical solutions of fluid dynamical problems. The paper discusses the challenges of defining fluid interfaces in multifluid Eulerian hydrodynamic calculations and highlights the simplicity and effectiveness of SLIC compared to other methods like PIC, CEL, and KRAKEN. SLIC's alternating-direction approach ensures that the limited information from the left and right neighbors is sufficient to construct reasonable representations of fluid surface configurations.SLIC (Simple Line Interface Calculation) is an alternating-direction method for geometrically approximating fluid interfaces in one, two, or three space dimensions. Key features of SLIC include: 1. Fluid surfaces are locally represented for each mixed-fluid zone, defined as a composition of one-dimensional components in each coordinate direction. 2. These one-dimensional components are composed entirely of straight lines, either perpendicular or parallel to the coordinate direction. 3. The one-dimensional surface approximations for a mixed fluid cell are determined by testing the presence or absence of fluids in the adjacent zones. 4. The one-dimensional nature of SLIC simplifies the time advancement of fluid surfaces, making it practical for numerical solutions of fluid dynamical problems. The paper discusses the challenges of defining fluid interfaces in multifluid Eulerian hydrodynamic calculations and highlights the simplicity and effectiveness of SLIC compared to other methods like PIC, CEL, and KRAKEN. SLIC's alternating-direction approach ensures that the limited information from the left and right neighbors is sufficient to construct reasonable representations of fluid surface configurations.