Method for cutting a patch from a planar film, said patch being intended to be applied to a curved face of a substrate, which face is bounded by a peripheral edge, the method comprising a step consisting in transferring an outline to the film and cutting the patch depending on said outline, characterized in that it comprises the following steps: /1/ obtaining the three-dimensional coordinates of a set of points forming a mesh of the face of the substrate; /2/ defining a reference point on the face of the substrate, a reference axis (Δ 0) passing through the face of the substrate at said reference point, a reference plane (Π 0) tangent to the face of the substrate at said reference point, and a series of sampling points (B 1, B 2, B 3,...) along the peripheral edge of said face of the substrate; the following steps /3/ to /5/ being carried out for each sampling point (B 1, B 2, B 3,...) on the peripheral edge: /3/ defining a development plane (Π 1, Π 2, Π 3,...) containing the reference axis (Δ 0) and passing through said sampling point (B 1, B 2, B 3,...) on the peripheral edge; /4/ from the coordinates obtained in step /1/ of the points of the mesh, calculating a curvilinear length (l 1, 12, l 3,...), between the reference point and said sampling point (B 1, B 2, B 3,...) on the peripheral edge, by following a curved segment (S 1, S 2, S 3,...) of intersection of the face of the substrate with the development plane (Π 1, Π 2, Π 3,...); /5/ transferring the curvilinear length (l 1, l 2, l 3,...) from the reference point, along a rectilinear line (Δ 1, Δ 2. Δ 3,...) of intersection between the development plane (Π 1, Π 2, Π 3,...) and the reference plane (Π 0) so as to form a rectilinear segment (Σ 1, Σ 2, Σ 3,...) originating from said reference point and having the length calculated in step /4/; the method then comprising the following steps: /6/ connecting those ends (C 1, C 2, C 3...) of the rectilinear segments (Σ 1, Σ 2, Σ 3,...) which are opposite the reference point with an interpolation outline contained in the reference plane (Π 0); and /7/ transferring the interpolation outline to the film and cutting the patch depending on said interpolation outline. /1/ obtaining the three-dimensional coordinates of a set of points forming a mesh of the face of the substrate; /2/ defining a reference point on the face of the substrate, a reference axis (Δ 0) passing through the face of the substrate at said reference point, a reference plane (Π 0) tangent to the face of the substrate at said reference point, and a series of sampling points (B 1, B 2, B 3,...) along the peripheral edge of said face of the substrate; /3/ defining a development plane (Π 1, Π 2, Π 3,...) containing the reference axis (Δ 0) and passing through said sampling point (B 1, B 2, B 3,...) on the peripheral edge; /4/ from the coordinates obtained in step /1/ of the points of the mesh, calculating a curvilinear length (l 1, 12, l 3,...), between the reference point and said sampling point (B 1, B 2, B 3,...) on the peripheral edge, by following a curved segment (S 1, S 2, S 3,...) of intersection of the face of the substrate with the development plane (Π 1, Π 2, Π 3,...); /5/ transferring the curvilinear length (l 1, l 2, l 3,...) from the reference point, along a rectilinear line (Δ 1, Δ 2. Δ 3,...) of intersection between the development plane (Π 1, Π 2, Π 3,...) and the reference plane (Π 0) so as to form a rectilinear segment (Σ 1, Σ 2, Σ 3,...) originating from said reference point and having the length calculated in step /4/; /6/ connecting those ends (C 1, C 2, C 3...) of the rectilinear segments (Σ 1, Σ 2, Σ 3,...) which are opposite the reference point with an interpolation outline contained in the reference plane (Π 0); and /7/ transferring the interpolation outline to the film and cutting the patch depending on said interpolation outline.