1. A graphics processing subsystem, comprising: a renderer operable to render a primitive surface representable by a three-dimensional (3D) clipmap; a geometry shader (GS) configured to select respective major-plane viewports for a plurality of clipmap levels, said major-plane viewports being sized to represent full spatial extents of said 3D clipmap relative to a render target (RT) for said plurality of clipmap levels; a rasterizer configured to employ said respective major-plane viewports and said RT to rasterize a projection of said primitive surface onto a major plane to provide a projection area corresponding to said respective major-plane viewports into pixels representing fragments of said primitive surface for each of said plurality of clipmap levels; and a plurality of pixel shader (PS) instances configured to transform said fragments into respective voxels in said plurality of clipmap levels, thereby voxelizing said primitive surface.