A computer-implemented method for replicating a three-dimensional label mask for a three-dimensional volume dataset in a network of computing devices (101 to 10n), comprising: upon a first computing device joining a collaborative session on the network, initializing the first computing device with the entire dataset of the current label mask and the three-dimensional volume dataset; receiving, at the first computing device, a series of segmentation input data generated by a second computing device, wherein particular segmentation input data comprises current position data, size data and a label identifier associated with a sphere-shaped segmentation object used by the second computing device for interactively editing the label mask; replicating, at the first computing device, the edited label mask of the second computing device associated with the series of segmentation input data by: for each segmentation input data of the series, computing a respective ellipsoid which corresponds to the sphere-shaped segmentation object stretched inverse proportionally to the shape of voxels in the label mask; determining voxels (vi) of the label mask having a position inside the segmentation object based on the ratios of the distances between a respective voxel position and the center position of the ellipsoid in all three dimensions as numerators divided by the respective semi-axis length of the ellipsoid as denominators, each semi-axis length being a floating-point number represented by integer numbers for sign, significand and exponent, wherein the divisions are executed on a graphical processing unit of the first computing device by approximating the multiplicative inverse of the respective denominators by negating the exponents of the respective semi-axis lengths using bitwise operations, and multiplying the approximated multiplicative inverse of the respective denominators with their respective numerators; and updating, in the replicated label mask, the determined voxels in accordance with the label identifier of the segmentation input data. upon a first computing device joining a collaborative session on the network, initializing the first computing device with the entire dataset of the current label mask and the three-dimensional volume dataset; receiving, at the first computing device, a series of segmentation input data generated by a second computing device, wherein particular segmentation input data comprises current position data, size data and a label identifier associated with a sphere-shaped segmentation object used by the second computing device for interactively editing the label mask; replicating, at the first computing device, the edited label mask of the second computing device associated with the series of segmentation input data by: for each segmentation input data of the series, computing a respective ellipsoid which corresponds to the sphere-shaped segmentation object stretched inverse proportionally to the shape of voxels in the label mask; determining voxels (vi) of the label mask having a position inside the segmentation object based on the ratios of the distances between a respective voxel position and the center position of the ellipsoid in all three dimensions as numerators divided by the respective semi-axis length of the ellipsoid as denominators, each semi-axis length being a floating-point number represented by integer numbers for sign, significand and exponent, wherein the divisions are executed on a graphical processing unit of the first computing device by approximating the multiplicative inverse of the respective denominators by negating the exponents of the respective semi-axis lengths using bitwise operations, and multiplying the approximated multiplicative inverse of the respective denominators with their respective numerators; and updating, in the replicated label mask, the determined voxels in accordance with the label identifier of the segmentation input data. computing a respective ellipsoid which corresponds to the sphere-shaped segmentation object stretched inverse proportionally to the shape of voxels in the label mask; determining voxels (vi) of the label mask having a position inside the segmentation object based on the ratios of the distances between a respective voxel position and the center position of the ellipsoid in all three dimensions as numerators divided by the respective semi-axis length of the ellipsoid as denominators, each semi-axis length being a floating-point number represented by integer numbers for sign, significand and exponent, wherein the divisions are executed on a graphical processing unit of the first computing device by approximating the multiplicative inverse of the respective denominators by negating the exponents of the respective semi-axis lengths using bitwise operations, and multiplying the approximated multiplicative inverse of the respective denominators with their respective numerators; and updating, in the replicated label mask, the determined voxels in accordance with the label identifier of the segmentation input data.