A magnetic assembly for producing an optical effect layer exhibiting an ortho-parallactic effect on a substrate surface, said magnetic assembly comprising: a) a first magnetic-field generating device comprising n sets of spaced apart bar dipole magnets, with n being an integer equal to or bigger than 1, wherein each of said bar dipole magnets has its North-South magnetic axis substantially parallel to the substrate surface, wherein, for each set of said n sets, bar dipole magnets have their North pole pointing in a same direction and are substantially parallel to each other, and wherein the bar dipole magnets of the first magnetic-field generating device are at least partially or fully embedded in a polygonal-shaped supporting matrix, and b) a second magnetic-field generating device comprising one or more square-shaped or rectangle-shaped dipole magnets having their North-South magnetic axis substantially parallel to the substrate surface; wherein the vector sum H1 of the magnetic axes of the bar dipole magnets of the first magnetic-field generating device and the vector sum H2 of the one or more square-shaped or rectangle-shaped dipole magnets form an angle α in the range from about 5° to about 175° or in the range from about 185° to about 355°, preferably in the range from about 60° to about 120° or in the range from about 240° to about 300°, wherein the first magnetic-field generating device is placed below or on top of the second magnetic-field generating device, and wherein the first magnetic-field generating device and the second magnetic-field generating device are stacked with respect to one another. a) a first magnetic-field generating device comprising n sets of spaced apart bar dipole magnets, with n being an integer equal to or bigger than 1, wherein each of said bar dipole magnets has its North-South magnetic axis substantially parallel to the substrate surface, wherein, for each set of said n sets, bar dipole magnets have their North pole pointing in a same direction and are substantially parallel to each other, and wherein the bar dipole magnets of the first magnetic-field generating device are at least partially or fully embedded in a polygonal-shaped supporting matrix, and wherein each of said bar dipole magnets has its North-South magnetic axis substantially parallel to the substrate surface, wherein, for each set of said n sets, bar dipole magnets have their North pole pointing in a same direction and are substantially parallel to each other, and wherein the bar dipole magnets of the first magnetic-field generating device are at least partially or fully embedded in a polygonal-shaped supporting matrix, and b) a second magnetic-field generating device comprising one or more square-shaped or rectangle-shaped dipole magnets having their North-South magnetic axis substantially parallel to the substrate surface; wherein the vector sum H1 of the magnetic axes of the bar dipole magnets of the first magnetic-field generating device and the vector sum H2 of the one or more square-shaped or rectangle-shaped dipole magnets form an angle α in the range from about 5° to about 175° or in the range from about 185° to about 355°, preferably in the range from about 60° to about 120° or in the range from about 240° to about 300°, wherein the first magnetic-field generating device is placed below or on top of the second magnetic-field generating device, and wherein the first magnetic-field generating device and the second magnetic-field generating device are stacked with respect to one another. wherein the vector sum H1 of the magnetic axes of the bar dipole magnets of the first magnetic-field generating device and the vector sum H2 of the one or more square-shaped or rectangle-shaped dipole magnets form an angle α in the range from about 5° to about 175° or in the range from about 185° to about 355°, preferably in the range from about 60° to about 120° or in the range from about 240° to about 300°, wherein the first magnetic-field generating device is placed below or on top of the second magnetic-field generating device, and wherein the first magnetic-field generating device and the second magnetic-field generating device are stacked with respect to one another.