Iso 2.0 [3/12]: Extruded 3D Box Nano Rendering (stone-wall, cathedral-wall, homestead-wall)

[putersdcat]

Spec reference

IsoRenderingPlanV2.1.md §3.3 Extruded Nano; §3.4.1 Stone Wall; §Addendum A §3

Goal

Extruded nano tiles render as a 3-face isometric box:

1. End cap face (further from camera, darker)
2. Front face (closer to camera, full brightness)
3. Top cap (flat iso projection at elevated Y, showing footprint fill)

Correct orientation for H vs V wall:

• Horizontal (straight-h): front face matrix (1, 0.5), cap at right end
• Vertical (straight-v): front face matrix (-1, 0.5), cap at bottom end

Technical requirements

• Geometry from wallBounds(variant) → wall footprint rects
• shouldDrawEndCap(variant) false for straight-h, straight-v, cross
• isVerticalWall(variant) controls matrix sign flip
• sideTextureSvg used for front + cap faces
• topTextureSvg uses clipDiamond at elevated screenY

Acceptance criteria (ALL required to close)

• render_nano_tile stone-wall straight-h → H box: front face brickwork, right end cap, flat stone top. NO Z-pinned billboard fallback.
• render_nano_tile stone-wall straight-v → V box: correct face matrix, cap at different end.
• render_nano_tile stone-wall corner-tr → corner: both arms meet at correct angle, end caps only on open ends.
• render_nano_tile stone-wall cross → cross: no end caps (4-way join), 4 front face segments, full top.
• render_nano_tile cathedral-wall straight-h → cathedral palette (dark stone).
• render_nano_tile homestead-wall straight-h → homestead palette (timber/plaster).
• All PNGs committed to ProgressEvaluations/: nano-stonewall-{variant}.png for at least 8 variants.

Verification command

render_nano_tile kind=stone-wall variant=straight-h outputPath=ProgressEvaluations/nano-stonewall-straight-h.png
render_nano_tile kind=stone-wall variant=corner-tr outputPath=ProgressEvaluations/nano-stonewall-corner-tr.png
render_nano_tile kind=stone-wall variant=cross outputPath=ProgressEvaluations/nano-stonewall-cross.png