feat(poc): render textures upright, --front camera, and Text via a glyph atlas#33
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…t via a glyph atlas Three rendering-correctness changes surfaced by the Web3D/NIST conformance visual sweep, all in the PoC consumer + the stbtt io module (core stays headless): * Texture vertical flip: stb_image decodes rows top-first but GL treats the first row as the texture bottom, so file textures rendered upside-down (ConformanceNist Geometry/Box/texture.x3d: VTS decal inverted). Flip on load. * --front: new flag that frames the scene from a canonical straight-on, bounding-sphere-fit front camera (overriding any authored Viewpoint), matching how the NIST set bakes its *-front.jpg references so screenshots line up. * Text rendering: add StbttGlyphAtlas to the x3d_stbtt io module — bakes an ASCII coverage atlas via stb_truetype and returns a FontMetrics with advances (raw hmtx/unitsPerEm, matching StbttFontMetrics) AND atlas UVs. The PoC consumes it through the FontMetrics seam + a uGlyphAtlas shader branch (alpha-tested coverage, material color). Text was a blank white bar; now renders real glyphs. The shared Liberation faces move to third_party/fonts/ (one copy for both the SDK text tests and the PoC, no duplication); x3d_stbtt now also builds under -DX3D_CPP_BUILD_POC=ON. NOTICE updated.
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Three rendering-correctness changes the NIST visual conformance sweep surfaced. All in the PoC consumer + the
x3d_stbttio module — the headless core is untouched.1. Texture vertical flip (bug)
stb_imagedecodes rows top-first but GL treats the first row as the texture bottom, so file textures rendered upside-down (ConformanceNist/Geometry/Box/texture.x3d: the VTS decal was inverted). Flip on load; the inlineSFImagepath is genuinely bottom-up and stays unflipped.2.
--frontcanonical cameraNew flag that frames the scene from a straight-on, bounding-sphere-fit front camera (overriding any authored Viewpoint), matching how the NIST set bakes its
*-front.jpgreferences so screenshots line up apples-to-apples.3. Text rendering (feature)
Text was a blank white bar. Adds
StbttGlyphAtlasto thex3d_stbttio module: it bakes an ASCII coverage atlas via stb_truetype and returns aFontMetricswith advances (rawhmtx/unitsPerEm, matchingStbttFontMetrics) and atlas UVs. The PoC consumes it through theFontMetricsseam + auGlyphAtlasshader branch (alpha-tested coverage, material color). Per the seam decision, rasterization lives in the io module, not core.The shared Liberation faces move to
third_party/fonts/— one copy for both the SDK text tests and the PoC (no duplication);FIXTURES_DIRupdated.x3d_stbttnow also builds under-DX3D_CPP_BUILD_POC=ON.NOTICEupdated.Verified:
build-ci111/111, full PoC build, and visual confirmation against the conformance references (textured box upright, "The VRML Test Suite" renders as glyphs).