Proposal:Variation on roofs

Proposal:Variation on roofs
Proposal status:	Draft (under way)
Proposed by:	Kovposch
Draft started:	2025-05-09

Proposal

Rationale

Problem

Currently, roofs with an inverted shape, or repeating patterns, can't be expressed concisely. The only specific solution widely supported now is roof:shape=sawtooth , with roof:shape=butterfly and roof:shape=wave etc discussed or proposed. Using a different word for each type has limited scalability, and requires more architectural knowledge of what they are called (eg can roof:shape=butterfly be roof:shape=seagull ? ).

When an inverted building only has an open inverted frame, with non-inverted structures inside, it could be ignored as a workaround, only drawing increasingly larger polygons for the enclosed space inside. But this doesn't solve inverted buildings with a smooth and solid exterior.

File:Upside_down_Pyramid,_Bratislava_02.jpg 5215475 5215475 https://demo.f4map.com/#lat=48.1549092&lon=17.1139213&zoom=19&camera.theta=79.141&camera.phi=2.865

roof:shape=gabled_row is criticized as unclear, meaning either row of "gabled", or roof:shape=sawtooth synonym Key:roof:shape#Values_with_problems

Solution

roof:shape:inverted=* and roof:shape:repeating=* would reuse existing basic types for both editing and application convenience. The special roof:shap=invertede and roof:shape=repeating follow how bridge=movable is used for openable bridges, to indicate they are special types that needs different handling. Applications can recognize them easily, and use a default model as a stand-in for those roof:shape:inverted=* and roof:shape:repeating=* they don't support yet.

Existing defined and supported roof:shape=sawtooth etc can continued to be used as a shortcut.

Tagging

Basic forms

(TBD: building:shape=* ?)

roof:shape=*
- roof:shape=inverted
- roof:shape=repeating
- roof:shape=*saltbox → roof:shape=trapezoid : Preferred to be clearer Key:roof:shape#Values_with_problems
  - roof:shape=saltbox → roof:shape=single_trapezoid
  - roof:shape=double_trapezoid
  - roof:shape=corner_trapezoid
  - roof:shape=triple_trapezoid
  - roof:shape=quadruple_saltbox → roof:shape=trapezoid
- roof:shape=wavelet : To be used when the roof only has a single "wave" packet