Abstract: A computer-implemented method for optimizing a design of a physical object comprises: obtaining a data representation of the design of the physical object, including a plurality of elements, determining plural element clusters comprising a plurality of elements and estimating a cost model for the physical object. The method determines derivatives of the cost model with respect to a material density of each cluster. At least one analytical derivative of a performance metric for each element is computed. The design is optimized by iteratively performing: varying the material density of at least one element based on the analytical derivative and the estimated derivatives of the cost model, estimating the cost using the cost model based on the data representation with varied material density. The method generates and outputs a signal comprising the optimized data representation in case a termination criterion has been met.