nx_tex_sample.nx

nx_tex_sample.nx -- UV texture sampling on Image (graphics). Distinct from nx_texture.nx (Haralick GLCM + LBP texture ANALYSIS for image classification). This file is texture SAMPLING for rendering -- the GLSL texture2D / HLSL Sample / Metal texture-access primitive. Completes the graphics minimum stack (nx_raster + nx_zbuf + this). Pure i64 substrate -- no FPU, no GPU. Substrate can now sample textures with bilinear filtering + wrap modes on any backend including Cortex-M3 with a framebuffer. L3 composition (bits-up): nx_image.Image (canonical pixel container, L1) nx_loop.LoopVerdict (bounded loops) ===== UV convention ============================================= (u, v) in Q10 fixed-point representing [0, 1) UV space. u_q10 = 0 -> left edge of texture u_q10 = 1024 -> right edge (exclusive) v_q10 = 0 -> top edge of texture v_q10 = 1024 -> bottom edge (exclusive) Q10 over Q14: bilinear weights need sub-pixel accuracy that 8-bit can't give; Q14 is too tight for clean integer multiplication; Q10 = sweet spot for the substrate's existing arithmetic. ===== Wrap modes (sealed enum) ================================== NX_TEX_WRAP_CLAMP -- saturate to [0, W-1] / [0, H-1] NX_TEX_WRAP_REPEAT -- modulo W / H (tile) NX_TEX_WRAP_MIRROR -- ping-pong: every other tile is flipped ===== Filter modes ============================================== NX_TEX_FILTER_NEAREST -- single texel lookup; fast, blocky NX_TEX_FILTER_BILINEAR -- 4-tap weighted average; smooth genealogy_id: catmull_smith_1980_texture_mapping +