Computer-implemented method for designing a three-dimensional modeled object that is an object without properties defined by mathematical equations, the three-dimensional object being created on a support by a stroke, the support being a surface in a three-dimensional scene, the method comprising: - user-interacting (S100) with a screen to activate pixels of the screen; - defining a stroke (S110) corresponding to the activated pixels of the screen; - discretizing the stroke (S120) into a set of points; - projecting the set of points (S130) onto at least one support in the three-dimensional scene; - constructing the three-dimensional modeled object (S140) from the projected set of points and the said at least one support by storing together in a CAD file the position of the projected set of points and coordinates of the support in the 3D scene; - constructing (S150) a visualization of the three-dimensional modeled object by computing by a GPU: - at least two offset points (S153) for each point of the projected set of points, an offset point being a point positioned on said at least one support and spaced from said each point; and - a surface (S155) delineated by the computed at least two offset points, the surface comprising the projected set of points; - displaying the constructed three-dimensional modeled object; - manipulating by the user the at least one support in the three-dimensional scene to create a second support that is a new support in the three-dimensional scene, another visualization of the three-dimensional modeled object being displayed in accordance with a new viewpoint; and - repeating the steps of the method with the second support in the three-dimensional scene. - user-interacting (S100) with a screen to activate pixels of the screen; - defining a stroke (S110) corresponding to the activated pixels of the screen; - discretizing the stroke (S120) into a set of points; - projecting the set of points (S130) onto at least one support in the three-dimensional scene; - constructing the three-dimensional modeled object (S140) from the projected set of points and the said at least one support by storing together in a CAD file the position of the projected set of points and coordinates of the support in the 3D scene; - constructing (S150) a visualization of the three-dimensional modeled object by computing by a GPU: - at least two offset points (S153) for each point of the projected set of points, an offset point being a point positioned on said at least one support and spaced from said each point; and - a surface (S155) delineated by the computed at least two offset points, the surface comprising the projected set of points; - at least two offset points (S153) for each point of the projected set of points, an offset point being a point positioned on said at least one support and spaced from said each point; and - a surface (S155) delineated by the computed at least two offset points, the surface comprising the projected set of points; - displaying the constructed three-dimensional modeled object; - manipulating by the user the at least one support in the three-dimensional scene to create a second support that is a new support in the three-dimensional scene, another visualization of the three-dimensional modeled object being displayed in accordance with a new viewpoint; and - repeating the steps of the method with the second support in the three-dimensional scene. <EOS>