Winter fir atlases

Two dedicated winter atlases now preserve snowy boughs when Alpine stage 03 switches from mesh trees to individual cards and forest groups. The textures were baked from the existing licensed fir source on CPU, inspected before publication, and connected through an explicit winter flag. Native LOD transition and complete scene appearance remain pending; this work does not establish AAA quality or correct the separate summer forest presentation.

Source and actual production

The source is Poly Haven Fir Tree 01, by Rico Cilliers (modeling) and Rob Tuytel (photography), CC0-1.0. The downloaded fir_tree_01_1k.blend has SHA256 153d20aae6d7c63a4c52689d91e8bead78f6d17a70e11ef4d03d19953383de00. Source and delivered hashes, exact camera settings, alpha statistics and render timings are in ALPINE-WINTER-FIR-ASSETS.json.

Tools/Art/bake_winter_fir.py rendered eight RGBA views in 38.266 seconds, using Blender 4.5.9 LTS, Cycles CPU, four threads and eight samples. Each view had a 60-second render limit. No Unity, player or GPU renderer was started. The editable packed source and individual renders remain under ArtSource/Alps/WinterFir; Tools/Art/prepare_winter_fir_delivery.py packs the exact render cells without scaling or recoloring.

The publisher's UVMap opens here as a generic corner-domain FLOAT_VECTOR attribute rather than an active Blender UV layer. For this source bake, the original per-corner X/Y values were copied exactly into an active UVMap; the original XYZ attribute was retained separately. This is an explicit source interpretation step, not a painted replacement texture. The subsequent, separate summer UV audit and repair proved the same import problem in the old summer bakes and delivered FBXs; those findings are not inferred from the winter atlas alone.

Snow is added only over twig-material triangles above branch-local 2.8 m with abs(normal.z) >= 0.42 in Blender's Z-up coordinates. Selected surfaces are raised by 0.025 m and downward faces reversed. Original photographic needle alpha cuts both the boughs and their snow covering; backfaces are transparent so dark undersides and trunks remain visible. No whole-tree white or green tint is applied. Source meshes are pre-decimation, so the coverage is equivalent in method, not triangle-identical to the decimated near runtime trees; the runtime FBX grounding offset is also retained unchanged.

Individual camera framing preserves each source's height, orthographic size at height × 1.04, 45 m radius and half-height target. Forest groups retain the existing seeds 1/2, 3 × 5 trees, random-call order, 50 m orthographic size, 90 m radius and 11 m camera/target elevation. The group atlas keeps its existing two-column layout. The individual winter atlas deliberately uses two columns; its runtime UVs use two, while existing summer UVs still use three.

Runtime integration and verification

AlpineFirAssets.Place, Far and ForestCluster select cached winter materials when requested. AlpineForestCanopy and the chapter groves pass that flag for stage index 2. Individual card cache keys separate summer and winter UV layouts. Both new materials use Color.white to preserve the baked branch-snow color and the existing upward card normals without HDRP backface flipping. Shader references are retained through AlpineWinterDressing.RepresentativeMaterials.

Texture import settings retain sRGB color, mipmaps with alpha coverage at 0.24, clamp, trilinear filtering, anisotropy 8 and a 2048 maximum size. Delivered SHA256 hashes were independently checked against the reviewed exports. Both atlases were visually inspected: snowy branch tops, dark trunks/undersides and transparent silhouettes are present. User winter references 06/07 were reviewed as an art target; an isolated atlas is not a complete-scene match.

The integrated source compiled with 91 Runtime + 20 Editor files, zero warnings and errors. No tree positions, densities, colliders, road geometry or summer atlas/card settings changed in this integration. The 18:04 Windows build predates these textures; native winter LOD and scene acceptance must use a later build.