A graphics processing subsystem and method for computing a 3D clipmap. One embodiment of the subsystem includes: (1) a renderer operable to render a primitive surface representable by a 3D clipmap, (2) a geometry shader (GS) configured to select respective major-plane viewports for a plurality of clipmap levels, the major-plane viewports being sized to represent full spatial extents of the 3D clipmap relative to a render target (RT) for the plurality of clipmap levels, (3) a rasterizer configured to employ the respective major-plane viewports and the RT to rasterize a projection of the primitive surface onto a major plane corresponding to the respective major-plane viewports into pixels representing fragments of the primitive surface for each of the plurality of clipmap levels, and (4) a plurality of pixel shader (PS) instances configured to transform the fragments into respective voxels in the plurality of clipmap levels, thereby voxelizing the primitive surface.