README.md

@@ -34,6 +34,9 @@ Importer status:
 
 - `ovp-text`: project-owned plain-text heightfield fixture format used for tests.
 - `hgt`: enabled by the optional `hgt` Cargo feature; parses SRTM HGT payloads as square grids of big-endian signed 16-bit metre samples. The implementation and tests use open specifications and synthetic/tiny fixtures only.
+- `geotiff`: enabled by the optional `import-geotiff` Cargo feature; parses single-band GeoTIFF elevation tiles in memory via the pure-Rust `geotiff-reader` crate (no GDAL, no native dependency). It supports a deliberately narrow subset — a single-band raster decoded as `f32` — and is reported by `openvistapro info` only when the feature is built.
+
+All importer tests use tiny synthetic, project-owned fixture data: HGT uses inline synthetic byte arrays, and the GeoTIFF tests generate a tiny single-band tile in memory rather than reading committed binaries or real geodata.
 
 To verify the importer feature surface:
 
@@ -42,6 +45,9 @@ cargo test hgt
 cargo test hgt --features hgt
 cargo run --features hgt --bin openvistapro -- info
 cargo test --no-default-features
+cargo test geotiff --features import-geotiff
+cargo run --features import-geotiff --bin openvistapro -- info
+cargo test --all-features
 ```
 
 The default `render` mode writes a deterministic top-down elevation preview.

docs/knowledgebase/architecture-notes.md

@@ -5,7 +5,7 @@
 Start simple, then split into crates when module boundaries stabilize.
 
 - `src/terrain.rs`: height grid, bounds, sampling, normals, terrain transforms.
-- `src/import/`: importers for open/safe formats; historical compatibility later.
+- `src/import/`: importers for open/safe formats; historical compatibility later. Implemented so far: the project-owned `ovp-text` heightfield, an SRTM/HGT byte parser behind the `hgt` feature, and an optional single-band GeoTIFF importer (`src/import/geotiff.rs`) behind the `import-geotiff` feature. Each importer yields the same internal `HeightGrid` plus `TerrainSourceMetadata`, keeping source formats out of renderer code.
 - `src/scene.rs`: camera, target, light, atmosphere, water, vegetation parameters.
 - `src/render/`: CPU reference renderer first, then WGPU renderer.
 - `src/script.rs`: parse and execute OpenVistaPro script commands.
@@ -20,7 +20,7 @@ Start simple, then split into crates when module boundaries stabilize.
 - `image` for PNG output and texture loading.
 - `nalgebra` or `glam` for vector/matrix math.
 - `wgpu` plus `winit`/`egui` for the eventual interactive app.
-- `gdal` support should be optional because native GDAL dependency setup can be heavy.
+- GeoTIFF support uses the pure-Rust `geotiff-reader` crate behind the optional `import-geotiff` feature, so default builds stay free of native dependencies. `gdal` is intentionally not used; any future GDAL-backed path would be a separate, opt-in feature because native GDAL setup can be heavy.
 
 ## Development strategy
 

docs/plans/phase-4-formats-scripts-ui.md

@@ -344,35 +344,52 @@ Run: `cargo test dem --features import-dem`
 
 Expected: PASS.
 
-### Task C3: Add GeoTIFF spike behind an optional feature
+### Task C3: GeoTIFF importer behind an optional feature (implemented)
 
-**Objective:** Decide whether to use a pure-Rust TIFF path or optional GDAL without making default builds fragile.
+**Status:** Done. Landed as the optional `import-geotiff` feature; this section
+records the implemented design. The crate survey behind it is
+[`docs/research/geotiff-import-strategy.md`](../research/geotiff-import-strategy.md).
+
+**Objective:** Parse single-band GeoTIFF elevation tiles into the internal
+`HeightGrid` without making default builds fragile or pulling a native
+dependency.
+
+**Outcome:** A pure-Rust path was chosen over GDAL. The importer uses the
+`geotiff-reader` crate (`local` feature, `cog`/network feature off), declared as
+an optional dependency gated by the `import-geotiff` Cargo feature. There is no
+GDAL dependency and no native toolchain requirement, so `import-geotiff` builds
+and tests run anywhere `cargo` runs — the "documented skip if native GDAL is not
+installed" escape hatch is not needed and is reserved for any future,
+separately reviewed GDAL-backed feature.
 
 **Files:**
-- Create: `src/import/geotiff.rs`
-- Modify: `Cargo.toml`
-- Modify: `docs/plans/phase-4-formats-scripts-ui.md` or follow-up notes if the spike changes direction
-- Test: tiny openly licensed or generated GeoTIFF fixture only if licensing is clear
+- `src/import/geotiff.rs`: `cfg(feature = "import-geotiff")` module exposing
+  `parse_geotiff_bytes(&[u8]) -> Result<ImportedTerrain, ImportError>`. It reads
+  the payload in memory, rejects non-single-band rasters, decodes the raster as
+  `f32`, and builds a `HeightGrid` plus `TerrainSourceMetadata` (format
+  `"geotiff"`). Reader/decode failures map to `ImportError::MalformedSource`.
+- `src/import.rs`: declares the `geotiff` submodule under the feature cfg.
+- `Cargo.toml`: `import-geotiff = ["dep:geotiff-reader"]`; `geotiff-writer` and
+  `ndarray` are dev-dependencies used only to generate the test fixture.
+- `src/cli.rs`: `supported_importers()` and `info_text()` list `geotiff` only
+  when the feature is built. (A `render --import-geotiff` flag mirroring the HGT
+  path remains future work.)
 
-**Step 1: Write failing test or spike acceptance check**
+**Fixture hygiene:** Tests do not commit any GeoTIFF binary. They generate a
+tiny single-band elevation tile in memory with `geotiff-writer` (dev-dependency)
+and parse it back, mirroring the synthetic-fixture approach used for HGT. No
+proprietary data and no large real-world DEMs enter the repository; real tiles
+may be used only for local manual verification under the already-ignored
+`reference/` and `.work/` directories.
 
-Prefer a generated fixture committed under an explicit license. If that is not practical, write parser-interface tests and keep the full fixture local until license is resolved.
+**Validation**
 
-**Step 2: Verify RED**
+Run: `cargo test --no-default-features`, `cargo test geotiff --features import-geotiff`,
+and `cargo test --all-features`.
 
-Run: `cargo test geotiff --features import-geotiff`
-
-Expected: FAIL until the selected crate and parser stub exist.
-
-**Step 3: Implement minimal code**
-
-Add only enough to detect/parse a tiny supported subset. If GDAL is required, keep the feature opt-in and document native setup.
-
-**Step 4: Verify GREEN**
-
-Run: `cargo test --features import-geotiff`
-
-Expected: PASS on systems with the optional dependency available, or a documented skip if native GDAL is not installed.
+Expected: default and `--no-default-features` builds stay GeoTIFF-free; the
+feature build and `--all-features` exercise the parser and pass without any
+native dependency.
 
 ## Milestone D: Scene/project metadata evolution
 

docs/research/geotiff-import-strategy.md

@@ -1,11 +1,13 @@
 # GeoTIFF Import Strategy Research Note
 
-> **Status:** Spike / decision note. Documentation-only — no code or `Cargo.toml`
-> changes accompany this note.
+> **Status:** Decision implemented. The recommended pure-Rust path has landed
+> as the optional `import-geotiff` feature; the crate survey below is kept for
+> provenance.
 >
-> **Context:** Phase 4 Milestone C, Task C3 ("Add GeoTIFF spike behind an
-> optional feature"). This note records the crate survey and the recommended
-> direction so the implementation slice can start from a settled decision.
+> **Context:** Phase 4 Milestone C, Task C3 ("GeoTIFF importer behind an
+> optional feature"). This note recorded the crate survey and recommended
+> direction; the "Implementation notes" section below describes what was
+> actually built.
 
 ## Recommendation
 
@@ -136,44 +138,48 @@ Consistent with Task C1's existing feature scaffold (`import-dem`,
 - The committed fixture should be only as large as the test needs (target:
   well under a kilobyte).
 
-## Follow-up implementation slice
+## Implementation notes
 
-Concrete next slice for Task C3, to be done TDD (RED → minimal GREEN →
-validation) on a separate implementation branch:
+The recommended pure-Rust path has landed. What was built:
 
-1. **Add the feature + dependency.** In `Cargo.toml`, make `geotiff-reader` an
-   optional dependency gated by `import-geotiff` (default `cog` feature
-   disabled). Confirm `cargo test --no-default-features` and the default build
-   stay GeoTIFF-free.
-2. **Create `src/import/geotiff.rs`.** A `cfg(feature = "import-geotiff")`
-   module exposing something like
-   `parse_geotiff_bytes(&[u8]) -> Result<ImportedTerrain, ImportError>`,
-   reusing the `ImportedTerrain` / `ImportError` / `TerrainSourceMetadata`
-   types from Milestone A.
-3. **Generate the synthetic fixture.** Add a tiny generated single-band
-   elevation GeoTIFF as a project-owned fixture (separate commit from the
-   parser, per the plan's commit strategy).
-4. **RED test.** `cargo test geotiff --features import-geotiff` — assert
-   dimensions, sample values, and metadata; assert malformed input yields a
-   typed error.
-5. **Minimal GREEN.** Parse only the tiny supported subset (single band,
-   uncompressed, known sample type). Reject everything else explicitly;
-   document that broad real-world GeoTIFF coverage is future work.
-6. **CLI plumbing (optional, can be a later slice).** Mirror the HGT pattern
-   (Task B3): an `--import-geotiff <path>` render input, gated so it only
-   appears when the feature is built.
-7. **Validation.** `cargo test --no-default-features`,
-   `cargo test --features import-geotiff`, `cargo test --all-features`,
-   `cargo fmt --check`, `cargo clippy --all-targets -- -D warnings`,
-   `git diff --check`.
-8. **Update `openvistapro info`** to report GeoTIFF support honestly — only
-   once a real parser and fixture exist (consistent with Task A3).
+1. **Feature + dependency.** `Cargo.toml` declares
+   `import-geotiff = ["dep:geotiff-reader"]`; `geotiff-reader` is an optional
+   dependency built with its `local` feature and `default-features = false`, so
+   the network-oriented `cog` feature stays off. Default and
+   `--no-default-features` builds remain GeoTIFF-free.
+2. **`src/import/geotiff.rs`.** A `cfg(feature = "import-geotiff")` module
+   exposing `parse_geotiff_bytes(&[u8]) -> Result<ImportedTerrain, ImportError>`,
+   reusing the `ImportedTerrain` / `ImportError` / `TerrainSourceMetadata` types
+   from Milestone A. It reads the payload in memory, rejects rasters that are
+   not single-band, decodes the raster as `f32` into a row-major `HeightGrid`,
+   and records `TerrainSourceMetadata` with format `"geotiff"`. Reader and
+   decode failures map to `ImportError::MalformedSource`.
+3. **Synthetic fixtures only.** No GeoTIFF binary is committed. Tests generate a
+   tiny single-band elevation tile in memory with the `geotiff-writer`
+   dev-dependency (alongside `ndarray`) and parse it back — mirroring the
+   inline-bytes approach used for HGT. Real USGS/NASA tiles may be used for
+   local manual verification only, under the already-ignored `reference/` and
+   `.work/` directories.
+4. **Tests.** `cargo test geotiff --features import-geotiff` asserts dimensions,
+   sample values, and metadata, and checks that non-GeoTIFF input yields a typed
+   `ImportError::MalformedSource`.
+5. **Supported subset.** Only the narrow single-band `f32` case is parsed;
+   broader real-world GeoTIFF coverage (multi-band, exotic compression, full
+   geo-tag interpretation) remains future work.
+6. **`openvistapro info`.** `supported_importers()` and `info_text()` list
+   `geotiff` only when the feature is built, keeping `info` honest.
+7. **GDAL is not part of the landed feature.** The importer has zero native
+   dependencies; a GDAL-backed path stays out of scope until a separate review
+   approves the native-dependency cost, and would use its own opt-in feature
+   name rather than `import-geotiff`.
 
-If `geotiff-reader` proves insufficient during the spike (missing geo-tag
-coverage, API gaps), fall back in this order: `georaster` → `wbgeotiff` →
-hand-rolled geo-tag reading on top of `image`'s TIFF decoder. A GDAL-backed
-path stays out of scope until a separate review approves the native-dependency
-cost.
+**Not yet done:** CLI render plumbing. A `render --import-geotiff <path>` input
+mirroring the HGT pattern (Task B3) is still future work; the parser is reachable
+through the library API and reported by `info`, but not yet wired into `render`.
+
+If `geotiff-reader` later proves insufficient (missing geo-tag coverage, API
+gaps), the documented fallback order remains `georaster` → `wbgeotiff` →
+hand-rolled geo-tag reading on top of `image`'s TIFF decoder.
 
 ## Sources