A computer implemented method of simulating a stack of objects represented as data within memory of a computer system is disclosed. The method comprises modeling the stack within a computer simulation as a set of associated primitives with associated constraints thereto in the memory, wherein the stack comprises a plurality of layers and wherein each layer comprises at least one primitive. The method further comprises estimating a height for each of the primitives in the stack and determining a respective scaling factor for each of the primitives in parallel, wherein each scaling factor is operable to adjust a mass value of each of the primitives. Also, the method comprises scaling a mass value of each of the primitives in accordance with a respective scaling factor in parallel. Finally, the method comprises solving over a plurality of constraints iteratively using a scaled mass value for each of the primitives.