Three fixes to match retail CLandBlock::get_land_scenes (0x00530460):
1. Loop bound: iterate 9×9 vertices (side_vertex_count=9), not 8×8
cells. Edge vertices (x=8 or y=8) produce valid spawns when the
per-object displacement shifts the position back into [0, 192).
Confirmed by named retail decomp do-while condition, WorldBuilder
vertLength=9, ACViewer Terrain.Count=81, AC2D wTopo[9][9].
2. Building suppression: check at the DISPLACED position's cell
(CSortCell::has_building per spawn), not at the loop vertex index.
Matches WorldBuilder buildingsGrid[gx2, gy2] pattern.
3. Slope filter: replace finite-difference gradient approximation
with triangle-aware normal sampling via new static method
TerrainSurface.SampleNormalZFromHeightmap. Picks the correct
triangle via IsSplitSWtoNE, matching retail find_terrain_poly →
polygon->plane.N.z and WorldBuilder's GetNormal().
Tests: 5 new tests for SampleNormalZFromHeightmap (flat=1.0, sloped<1,
cross-validates with SampleSurface instance method) and DisplaceObject
edge-vertex validity.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
StepUpHeight: when Tab enters player mode, read Setup.StepUpHeight from the
player entity's dat and apply it to the controller (fallback 2f for non-Setup
entities or when the dat value is zero). Previously hardcoded to 5.0 which
made step-up too permissive.
Road exclusion: SceneryGenerator now skips terrain vertices where bits 0-1 of
the raw terrain word are non-zero. These bits encode the road type (GetRoad()
in ACViewer's Landblock.cs). Trees, rocks and bushes will no longer be placed
on road surfaces.
Added SceneryGenerator.IsRoadVertex(ushort) public helper + 9 unit tests
(theory + fact) verifying the road-bit convention matches TerrainInfo.Road.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
