The article considers the task of rendering function-based scenes with a sample of significance to reduce variance. A sampling method based on significance with an optimal density is proposed. Samples with optimal density are generated in an additional space mapping. An algorithm is used that allows you to nonlinear deform an additional space mapping with the calculation of optimal densities. The algorithm implements a change in the deformation integration variables. As a result, a method has been implemented that leads to an effective reduction of variance in functionally defined scenes.