A method of generating a data set for training a system to generate data of a polygonal mesh by adapting data of an input polygonal mesh for rendering computer-generated objects with improved data redundancy, comprising: obtaining data of a plurality of reference polygonal meshes for use in rendering a content, each reference polygonal mesh comprising a plurality of vertices for representing a surface in the content; for each reference polygonal mesh: determining a vertex count of the reference polygonal mesh; generating a second polygonal mesh by adding a predetermined number of vertices to the reference polygonal mesh; comparing a representation of the second polygonal mesh with a representation of the reference polygonal mesh; assigning a first value of a quality parameter to the reference polygonal mesh, and assigning a second value of the quality parameter to the second polygonal mesh based on the comparison of the representations, the value of the quality parameter for a given polygonal mesh indicative of a degree of difference between a representation of the given polygonal mesh and a representation of the reference polygonal mesh; and generating a data set comprising data indicative of the vertex count for the reference and second polygonal meshes and the value of the quality parameters for the reference and second polygonal meshes. obtaining data of a plurality of reference polygonal meshes for use in rendering a content, each reference polygonal mesh comprising a plurality of vertices for representing a surface in the content; for each reference polygonal mesh: determining a vertex count of the reference polygonal mesh; generating a second polygonal mesh by adding a predetermined number of vertices to the reference polygonal mesh; comparing a representation of the second polygonal mesh with a representation of the reference polygonal mesh; assigning a first value of a quality parameter to the reference polygonal mesh, and assigning a second value of the quality parameter to the second polygonal mesh based on the comparison of the representations, the value of the quality parameter for a given polygonal mesh indicative of a degree of difference between a representation of the given polygonal mesh and a representation of the reference polygonal mesh; and generating a data set comprising data indicative of the vertex count for the reference and second polygonal meshes and the value of the quality parameters for the reference and second polygonal meshes. determining a vertex count of the reference polygonal mesh; generating a second polygonal mesh by adding a predetermined number of vertices to the reference polygonal mesh; comparing a representation of the second polygonal mesh with a representation of the reference polygonal mesh; assigning a first value of a quality parameter to the reference polygonal mesh, and assigning a second value of the quality parameter to the second polygonal mesh based on the comparison of the representations, the value of the quality parameter for a given polygonal mesh indicative of a degree of difference between a representation of the given polygonal mesh and a representation of the reference polygonal mesh; and generating a data set comprising data indicative of the vertex count for the reference and second polygonal meshes and the value of the quality parameters for the reference and second polygonal meshes.