Systems, methods, and non-transitory computer-readable media are disclosed for modifying voxel-based 3D representations using 3D digital brush tools and/or resolution filters. For example, the disclosed systems can utilize 3D digital brush tools (e.g., a digital blur brush tool, a digital smudge brush tool, and/or a digital melt brush tool) to identify and modify one or more voxels within a 3D representation using multiple buffers of visual properties. Additionally, the disclosed systems can modify one or more voxels within a 3D representation by rendering the one or more voxels at varying levels of detail using an octree (e.g., a mosaic filter tool). In particular, the disclosed systems can identify one or more voxels within an octree that are smaller than a target voxel size. Moreover, the disclosed systems can combine the identified one or more voxels within the octree to render the 3D representation at varying levels of detail.