Mature tree stem proportions

The user's crop and the full native QA/20260916-110529-graphics-all-levels/alps-02-view2.png were inspected. The most conspicuous tall thin trees are the near imported firs, not just distant broadleaf cards. Scaling their whole crowns wider would not correct their exposed stems.

One read-only Blender source inspection of the five delivered FBX meshes, with no render or asset export, is recorded in ArtSource/Alps/StemProportions/source-profiles.json. The 18.96 m source fir has a broad root flare, but its median shaft radius is about 0.13 m at 1.4 m height and 0.09 m at 4.7 m. This explains the long thin exposed shafts. Broadleaf wood also uses young-tree proportions, and its most reduced LOD2 collapses most of the lower stem to isolated vertices, beginning 0.21 source metres above ground.

TreeStemGeometry measures horizontal triangle cross-sections of LOD0 wood, follows the stem centreline and builds shared radial shape variants for six height classes from 6–26 m. Only actual wood vertices move, and only horizontally. Radius follows requested tree height, with root flare, gradual taper and a smooth return to the original upper trunk/fork. Original bark UVs, tree height, ground placement, crowns, branch geometry beyond the lower fork and all colliders stay in place. Imported FBX assets are not overwritten, and there are no new overlapping cylinder trunks.

Fir LOD0/1 use the original trunk triangle counts. Broadleaf trees at least 8 m high retain the 1,800-triangle LOD1 wood beneath the 600-triangle LOD2 crown, replacing the collapsed 797-triangle wood. Thus that particular representation adds 1,003 wood triangles per such tree; other source counts remain. Trees below 4 m, including shrubs, remain unchanged. Scene batches consume the shared shaped wood, while actual near tree LOD renderers share the same cached variants.

Far whole-tree billboards sample a wider lower trunk region of their existing photographic atlas. This shared sample mapping runs identically in colour, depth and motion-vector passes, fades before the crown and leaves the original root flare and crown width intact. It is an approximation to the shaped mesh, not a freshly photographed or physically relit tree. Material atlas column counts remain explicit for summer fir, winter fir and broadleaf. The reproducible shader-generation script is updated as well.

The shared tree batching API also accepts optional shadow casting for the separately authored near China forest. The default behavior of existing callers is unchanged.

Root owns compilation, native shader checks and the next visual capture. This implementation is not yet claimed as rendered acceptance. Inspect Alps02 view2 for proportional shaft thickness and grounding, broadleaf forks and near/far transitions for visible jumps, and the larger China trees for shade and geometry cost. No new Unity or Player process was launched by this subtask.