nx_zbuf.nx

nx_zbuf.nx -- depth buffer + Z-tested triangle rasterizer. Composes nx_raster (b3f83291) + nx_image.ImageS64 (depth buffer container) to close the 3D-RENDERING gap on top of 2D rasterization. Pure i64 substrate -- no FPU, no GPU. Software 3D renderer minimum: depth buffer + per-vertex Z interpolation + depth test. Composes: nx_image.Image (color framebuffer, L1) nx_image.ImageS64 (depth buffer, L1 -- signed i64 storage) nx_raster._rast_edge (canonical edge function from L2) nx_loop.LoopVerdict (bounded loops) ===== Math ====================================================== Per-vertex depth values z_a / z_b / z_c are provided by the caller (in raw i64 -- caller chooses units; typically the view-space Z * Q10 fixed-point). At pixel (px, py) the interpolated depth is: z_interp = (w0 * z_a + w1 * z_b + w2 * z_c) / area where w_i are the same edge functions nx_raster uses for the inside test. Smaller z = closer to viewer (standard less-than-or-equal depth test). Depth test: write color iff z_interp < z_buf[px, py]. ===== Initial value ============================================= The depth buffer starts at "infinity." i64 max = 0x7FFFFFFFFFFFFFFF. First write of any triangle's pixel is always accepted because any real Z < INFINITY. Caller must clear the buffer to FAR at the start of each frame via nx_zbuf_clear. Per the bits-up cardinal: no inline rasterizer here -- we COMPOSE _rast_edge from nx_raster.nx (NOT duplicate the algorithm). genealogy_id: catmull_1974_subdivision_z_buffer + pineda_1988_edge_function + blinn_1996_painters_algorithm_critique