feat(pj_base): add VoxelGrid canonical builtin object (SDK 0.10.0) (#130)

* feat(pj_base): add VoxelGrid canonical builtin object + codec

Add sdk::VoxelGrid, the dense 3D voxel-grid builtin — the volumetric
sibling of OccupancyGrid, reusing PointCloud's PointField channel model.
The struct mirrors foxglove.VoxelGrid's byte layout (Z-Y-X order, three
strides) so a lazily-parsing producer exposes `data` as a zero-copy
Span<const uint8_t> + BufferAnchor rather than transcoding cells. The
per-voxel value is generic (occupancy/cost/ESDF/semantic via `fields`);
which voxels are drawn stays a viewer-side decision.

- voxel_grid.hpp / voxel_grid_codec.{hpp,cpp} + proto/pj/VoxelGrid.proto
- kVoxelGrid = 18 appended to BuiltinObjectType and PJ_builtin_object_type_t
  (append-only; type 2 stays reserved)
- round-trip + empty-buffer tests; builtin_object_test enumerations extended
- docs: builtin_type.md (type row, section, conversion), proto README,
  builtin-count bumps + 3-source version mechanics in CLAUDE.md

Build Debug+ASAN green; voxel_grid_codec_test 4/4, builtin_object_test 6/6.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* chore(release): bump version to 0.10.0

VoxelGrid is a backward-compatible addition (tail-appended enum value +
two new exported symbols), so this is a MINOR bump and abi/baseline.abi
is unchanged.

Aligns all three version sources — conanfile.py, CMakeLists.txt
(PJ_PACKAGE_VERSION), and recipe.yaml (context.version) — so a v0.10.0
tag passes the conda-release guard. recipe.yaml had drifted to 0.8.1 at
the v0.9.0 tag, which is why the conda/pixi 0.9.0 publish failed while the
Conan/GitHub release succeeded.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: facontidavide

CLAUDE.md

@@ -15,9 +15,9 @@ two modules below have no own CLAUDE.md.
 ### Modules
 
 - **pj_base** — vocabulary types (`Timestamp`, `DatasetId`, `Expected<T>`, `Span<T>`, type trees),
-  the canonical builtin object vocabulary (`pj_base/builtin/`: 16 struct headers — Image, DepthImage,
+  the canonical builtin object vocabulary (`pj_base/builtin/`: 17 struct headers — Image, DepthImage,
   PointCloud, CompressedPointCloud, OccupancyGrid(+Update), Mesh3D, VideoFrame, AssetVideo,
-  SceneEntities, RobotDescription, CameraInfo, Log, ImageAnnotations, FrameTransforms, PosesInFrame) and their 15
+  SceneEntities, RobotDescription, CameraInfo, Log, ImageAnnotations, FrameTransforms, PosesInFrame, VoxelGrid) and their 16
   wire codecs (RobotDescription carries source text as-is — no codec), the C-ABI protocol headers for
   DataSource/MessageParser/Toolbox + the C++ SDK base classes / host-view helpers built on them.
 - **pj_plugins** — host-side loaders + RAII handles + plugin discovery/catalog for four plugin
@@ -102,11 +102,14 @@ changes within `0.x`** — the next ABI/API break ships as `1.0.0`. So a plugin
 `[>=0.Y.Z <1.0.0]`. (Deliberately stricter than the usual "0.x may break" convention, because
 plugins pin against this SDK.)
 
-**Mechanics.** The version lives in two places that must stay in sync — `version` in `conanfile.py`
-and `PJ_PACKAGE_VERSION` in the root `CMakeLists.txt` (also update the example tag in the
-`conanfile.py` docstring). A non-MAJOR PR must not alter `abi/baseline.abi` beyond additions (verify
-with `abidiff`). Tagging and pushing a release is a separate, explicitly-authorized step — never tag
-or push a release without the user's go-ahead.
+**Mechanics.** The version lives in **three** places that must stay in sync — `version` in
+`conanfile.py`, `PJ_PACKAGE_VERSION` in the root `CMakeLists.txt`, and `context.version` in
+`recipe.yaml` (the conda/pixi package version `rattler-build` embeds; `pixi.toml` itself carries
+**no** version) — plus the example tag in the `conanfile.py` docstring. The `conda-release.yml`
+release job hard-fails ("Verify tag matches all version sources") if the `v*` tag and any of the
+three disagree, so a bump that misses `recipe.yaml` cannot be released. A non-MAJOR PR must not
+alter `abi/baseline.abi` beyond additions (verify with `abidiff`). Tagging and pushing a release is
+a separate, explicitly-authorized step — never tag or push a release without the user's go-ahead.
 
 ## Coding Conventions
 

CMakeLists.txt

@@ -111,7 +111,7 @@ endif()
 if(PJ_INSTALL_SDK)
   include(CMakePackageConfigHelpers)
 
-  set(PJ_PACKAGE_VERSION "0.9.0")
+  set(PJ_PACKAGE_VERSION "0.10.0")
   set(PJ_PACKAGE_CMAKE_DIR ${CMAKE_INSTALL_LIBDIR}/cmake/plotjuggler_sdk)
 
   install(EXPORT plotjuggler_sdkTargets

conanfile.py

@@ -6,7 +6,7 @@
   plugin_sdk   — umbrella for plugin authors (base + dialog SDK + parser SDK)
   plugin_host  — umbrella for host loaders (data_source/parser/toolbox/dialog)
 
-A consuming Conan recipe declares e.g. `plotjuggler_sdk/0.9.0` and then:
+A consuming Conan recipe declares e.g. `plotjuggler_sdk/0.10.0` and then:
 
     find_package(plotjuggler_sdk REQUIRED COMPONENTS plugin_sdk)
     target_link_libraries(my_plugin PRIVATE plotjuggler_sdk::plugin_sdk)
@@ -30,7 +30,7 @@
 
 class PlotjugglerSdkConan(ConanFile):
     name = "plotjuggler_sdk"
-    version = "0.9.0"
+    version = "0.10.0"
     # Apache-2.0 covers the whole SDK (pj_base + pj_plugins). See LICENSE.
     license = "Apache-2.0"
     url = "https://github.com/PlotJuggler/plotjuggler_sdk"

docs/builtin_type.md

@@ -85,7 +85,7 @@ Builtin objects fall into two serialization families:
 
 | Family | Current types | Storage model | Codec policy |
 |--------|---------------|---------------|--------------|
-| Byte-backed views | `Image`, `DepthImage`, `PointCloud`, `CompressedPointCloud`, `OccupancyGrid`, `OccupancyGridUpdate`, `Mesh3D`, `VideoFrame` | Header fields live in the SDK struct; payload bytes live behind `Span<const uint8_t>` plus `BufferAnchor`. | No mandatory canonical codec; preserve zero-copy views over ROS, MCAP, compressed image, point-cloud, or plugin-owned payloads. If conversion is unavoidable, allocate a new payload and anchor it. |
+| Byte-backed views | `Image`, `DepthImage`, `PointCloud`, `CompressedPointCloud`, `OccupancyGrid`, `OccupancyGridUpdate`, `VoxelGrid`, `Mesh3D`, `VideoFrame` | Header fields live in the SDK struct; payload bytes live behind `Span<const uint8_t>` plus `BufferAnchor`. | No mandatory canonical codec; preserve zero-copy views over ROS, MCAP, compressed image, point-cloud, or plugin-owned payloads. If conversion is unavoidable, allocate a new payload and anchor it. |
 | Owned values | `ImageAnnotations`, `FrameTransforms`, `SceneEntities`, `AssetVideo`, `RobotDescription`, `CameraInfo`, `PosesInFrame`; future marker types | SDK structs own their vectors/strings/scalars directly. | Add explicit codecs when canonical bytes are needed. Codecs serialize the owned value to the protobuf-wire payload described by the `.proto` contract, using shared private wire primitives. `RobotDescription` carries source-format text as-is (no canonical codec) — the format hint distinguishes URDF / SDF / MJCF. |
 
 Canonical `.proto` files live under `pj_base/proto/pj` and act as the wire
@@ -126,6 +126,7 @@ annotations, frame transforms, or no builtin object.
 | `kOccupancyGridUpdate` | `PJ::sdk::OccupancyGridUpdate` | Incremental sub-rectangle patch for a previously-published `OccupancyGrid`. |
 | `kLog` | `PJ::sdk::Log` | Textual log message (severity level + text + originating name). |
 | `kPosesInFrame` | `PJ::sdk::PosesInFrame` | Array of poses in one frame (PoseArray / particle clouds); styling is viewer-side. |
+| `kVoxelGrid` | `PJ::sdk::VoxelGrid` | Dense 3D voxel grid (occupancy/cost/ESDF/semantic); the volumetric sibling of `OccupancyGrid`. |
 
 `BuiltinObject` is `std::any`. Producers store a concrete builtin value in it;
 consumers recover the concrete type with `std::any_cast<T>(&object)` or ask
@@ -593,6 +594,40 @@ so no `BufferAnchor` is needed.
 `pj_base/builtin/poses_in_frame_codec.hpp` serializes and deserializes this
 type using the canonical `PJ.PosesInFrame` protobuf wire format.
 
+## VoxelGrid
+
+`VoxelGrid` is a dense 3D voxel grid placed in world coordinates — the
+volumetric sibling of `OccupancyGrid` — for 3D occupancy maps, costmaps,
+ESDFs, and semantic grids (e.g. `foxglove.VoxelGrid`, `costmap_2d/VoxelGrid`).
+
+It is a byte-backed view: the lattice of `column_count * row_count *
+slice_count` voxels lives in `data` (a `Span<const uint8_t>` + `BufferAnchor`)
+in depth-major, row-major **Z-Y-X** order (x fastest), and the per-voxel layout
+is described by `fields` — the same `PointField` channel model used by
+`PointCloud`. The byte layout mirrors `foxglove.VoxelGrid` (three strides +
+Z-Y-X order) so a parser can hand out `data` zero-copy rather than transcoding
+millions of cells; expanding occupied voxels into renderable primitives is a
+viewer-side concern.
+
+Unlike the 2D `OccupancyGrid` (which fixes `-1`/`0..100` cell semantics), the
+per-voxel **value is generic**: occupancy byte, RGBA, a float cost/intensity, a
+class id, etc. The draw predicate (which voxels are visible) and any colormap are
+viewer-side, so one type serves occupancy/cost/ESDF/semantic grids.
+
+| Field | Type | Notes |
+|-------|------|-------|
+| `timestamp_ns` | `Timestamp` | Time of the grid. `0` when the source had none. |
+| `frame_id` | `std::string` | Source coordinate frame; 3D consumers TF-transform from it. |
+| `origin` | `Pose` | Lower-front-left `(0,0,0)` corner of the grid in `frame_id`. |
+| `cell_size` | `Vector3` | Metric voxel size along x/y/z (meters); need not be cubic. |
+| `column_count` / `row_count` / `slice_count` | `uint32_t` | Voxels along x / y / z. |
+| `cell_stride` / `row_stride` / `slice_stride` | `uint32_t` | Byte spacing of a voxel / row / z-slice (padding allowed). |
+| `fields` | `std::vector<PointField>` | Per-voxel channel layout. |
+| `data` | `Span<const uint8_t>` + `BufferAnchor` | Packed voxel bytes in Z-Y-X order. |
+
+`pj_base/builtin/voxel_grid_codec.hpp` serializes and deserializes this type
+using the canonical `PJ.VoxelGrid` protobuf wire format.
+
 ## Conversion Examples
 
 | Source type | Canonical builtin type | Conversion intent |
@@ -612,6 +647,7 @@ type using the canonical `PJ.PosesInFrame` protobuf wire format.
 | ROS `std_msgs/String` on `/robot_description` (or matching name) carrying URDF XML | `RobotDescription` | Validate root element matches `format`, then carry the raw text + format hint. No mesh resolution at parse time. |
 | ROS `sensor_msgs/CameraInfo` | `CameraInfo` | Map K / D / R / P plus dimensions; correlate to the image topic by name. Sub-window (binning / ROI) is dropped. |
 | ROS `map_msgs/OccupancyGridUpdate` | `OccupancyGridUpdate` | Forward the cell-space patch (`x`/`y`/`width`/`height` + bytes); the consumer pairs it with the base grid and supplies origin/resolution. |
+| `foxglove.VoxelGrid` / `costmap_2d/VoxelGrid` | `VoxelGrid` | Map counts/strides/`cell_size`/`origin` into the struct; keep voxel bytes zero-copy in Z-Y-X order. The draw predicate is viewer-side. |
 
 The builtin type is the boundary object. After conversion, consumers should not
 need to know which third-party schema produced it.

pj_base/CLAUDE.md

@@ -1,10 +1,10 @@
 # pj_base — SDK vocabulary, builtin object schemas, and the C plugin ABI
 
-pj_base is the **Level 0** foundation and the **SDK boundary** for plugin authors. It owns: the zero-dependency vocabulary types (`Timestamp`, `DatasetId`, `Range`, `Expected<T>`, `Span`, `TypeTree`); the canonical *builtin object* schemas (`sdk::Image`, `PointCloud`, `DepthImage`, `OccupancyGrid`, `FrameTransforms`, … — 16 types) **and 15 of their wire codecs** (RobotDescription has none); and the **C ABI** primitives every plugin family speaks (`plugin_data_api.h` + the service registry) plus the C-ABI protocol headers for **three** families — `data_source_protocol.h`, `message_parser_protocol.h`, `toolbox_protocol.h`. The **Dialog** protocol header is the exception: it lives in `pj_plugins/dialog_protocol/`, not here. It also ships the C++ SDK base classes for DataSource and Toolbox; the MessageParser and Dialog base classes live in `pj_plugins`. Builds as a STATIC lib with **zero public deps** — `fast_float` is a `BUILD_INTERFACE` private impl detail of `parseNumber`. Must NOT depend on `pj_datastore`, `pj_plugins`, Qt, or any Conan runtime lib. This is a read-only submodule subtree: change it only when explicitly working in `plotjuggler_sdk`.
+pj_base is the **Level 0** foundation and the **SDK boundary** for plugin authors. It owns: the zero-dependency vocabulary types (`Timestamp`, `DatasetId`, `Range`, `Expected<T>`, `Span`, `TypeTree`); the canonical *builtin object* schemas (`sdk::Image`, `PointCloud`, `DepthImage`, `OccupancyGrid`, `VoxelGrid`, `FrameTransforms`, … — 17 types) **and 16 of their wire codecs** (RobotDescription has none); and the **C ABI** primitives every plugin family speaks (`plugin_data_api.h` + the service registry) plus the C-ABI protocol headers for **three** families — `data_source_protocol.h`, `message_parser_protocol.h`, `toolbox_protocol.h`. The **Dialog** protocol header is the exception: it lives in `pj_plugins/dialog_protocol/`, not here. It also ships the C++ SDK base classes for DataSource and Toolbox; the MessageParser and Dialog base classes live in `pj_plugins`. Builds as a STATIC lib with **zero public deps** — `fast_float` is a `BUILD_INTERFACE` private impl detail of `parseNumber`. Must NOT depend on `pj_datastore`, `pj_plugins`, Qt, or any Conan runtime lib. This is a read-only submodule subtree: change it only when explicitly working in `plotjuggler_sdk`.
 
 ## Layout
 - `include/pj_base/` — vocabulary primitives: `types.hpp`, `time.hpp` (absolute time spine: `Timepoint`/`Duration` + `fromRaw`/`toRaw`), `type_tree.hpp`, `dataset.hpp`, `expected.hpp`, `span.hpp`, `number_parse.hpp`, `assert.hpp`, `diagnostic_sink.hpp`, `buffer_anchor.hpp`.
-- `include/pj_base/builtin/` — the 16 builtin object struct headers (`*.hpp`; 17 enum values in `BuiltinObjectType`, value 2 reserved) + their 15 wire codecs (`*_codec.hpp`; RobotDescription has none) + the `BuiltinObject` (`std::any`) type-erased holder.
+- `include/pj_base/builtin/` — the 17 builtin object struct headers (`*.hpp`; 18 enum values in `BuiltinObjectType`, value 2 reserved) + their 16 wire codecs (`*_codec.hpp`; RobotDescription has none) + the `BuiltinObject` (`std::any`) type-erased holder.
 - `include/pj_base/sdk/` — C++ SDK over the ABI: DataSource + Toolbox `*_plugin_base.hpp`, `service_registry.hpp`/`service_traits.hpp`, host views, Arrow RAII holders, `testing/`.
 - `include/pj_base/*_protocol.h`, `plugin_data_api.h`, `builtin_object_abi.h`, `plugin_abi_export.hpp` — the stable C-ABI surface for DataSource/MessageParser/Toolbox (the Dialog protocol header lives in `pj_plugins/dialog_protocol/`).
 - `proto/pj/` — canonical `.proto` wire contracts for the builtin types (see its README).

pj_base/CMakeLists.txt

@@ -18,6 +18,7 @@ add_library(pj_base STATIC
   src/builtin/poses_in_frame_codec.cpp
   src/builtin/scene_entities_codec.cpp
   src/builtin/video_frame_codec.cpp
+  src/builtin/voxel_grid_codec.cpp
   src/number_parse.cpp
   src/type_tree.cpp
 )
@@ -105,6 +106,7 @@ if(PJ_BUILD_TESTS)
     tests/asset_video_codec_test.cpp
     tests/time_spine_test.cpp
     tests/poses_in_frame_codec_test.cpp
+    tests/voxel_grid_codec_test.cpp
   )
 
   foreach(test_src ${PJ_BASE_TESTS})

pj_base/include/pj_base/builtin/builtin_object.hpp

@@ -42,6 +42,7 @@
 #include "pj_base/builtin/robot_description.hpp"
 #include "pj_base/builtin/scene_entities.hpp"
 #include "pj_base/builtin/video_frame.hpp"
+#include "pj_base/builtin/voxel_grid.hpp"
 
 namespace PJ {
 namespace sdk {
@@ -64,6 +65,7 @@ enum class BuiltinObjectType : uint16_t {
   kOccupancyGridUpdate = 15,  ///< sdk::OccupancyGridUpdate — incremental sub-rectangle patch for an OccupancyGrid.
   kLog = 16,                  ///< sdk::Log — textual log message (level + text + name).
   kPosesInFrame = 17,         ///< sdk::PosesInFrame — array of poses in one reference frame.
+  kVoxelGrid = 18,            ///< sdk::VoxelGrid — dense 3D voxel grid (occupancy/cost/ESDF/semantic).
 };
 
 /// A-priori classification of a schema. Currently carries only the type;
@@ -110,6 +112,8 @@ struct SchemaClassification {
       return "kLog";
     case BuiltinObjectType::kPosesInFrame:
       return "kPosesInFrame";
+    case BuiltinObjectType::kVoxelGrid:
+      return "kVoxelGrid";
   }
   return "kNone";
 }
@@ -168,6 +172,9 @@ struct SchemaClassification {
   if (s == "kPosesInFrame") {
     return BuiltinObjectType::kPosesInFrame;
   }
+  if (s == "kVoxelGrid") {
+    return BuiltinObjectType::kVoxelGrid;
+  }
   return std::nullopt;
 }
 
@@ -229,6 +236,9 @@ using BuiltinObject = std::any;
   if (t == typeid(PosesInFrame)) {
     return BuiltinObjectType::kPosesInFrame;
   }
+  if (t == typeid(VoxelGrid)) {
+    return BuiltinObjectType::kVoxelGrid;
+  }
   return BuiltinObjectType::kNone;
 }
 

pj_base/include/pj_base/builtin/voxel_grid.hpp

@@ -0,0 +1,70 @@
+/**
+ * @file voxel_grid.hpp
+ * @brief Dense 3D voxel grid placed in world coordinates.
+ */
+// Copyright 2026 Davide Faconti
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+#include "pj_base/buffer_anchor.hpp"
+#include "pj_base/builtin/frame_transforms.hpp"  // for Pose, Vector3
+#include "pj_base/builtin/point_cloud.hpp"       // for PointField (shared channel descriptor)
+#include "pj_base/span.hpp"
+#include "pj_base/types.hpp"
+
+namespace PJ {
+namespace sdk {
+
+/// Dense 3D voxel grid placed in world coordinates — the volumetric sibling of
+/// OccupancyGrid, reusing PointCloud's per-channel field model (`PointField`).
+///
+/// The grid is a regular lattice of `column_count * row_count * slice_count`
+/// voxels. Each voxel occupies `cell_stride` bytes laid out per `fields`; cells
+/// are stored densely in depth-major, row-major **Z-Y-X** order (x varies
+/// fastest), matching the foxglove.VoxelGrid wire layout so a parser can expose
+/// `data` as a zero-copy view rather than transcoding millions of cells.
+///
+/// Strides (in bytes) describe the packing and allow trailing padding:
+///   cell_stride  : one voxel        (>= sum of field element sizes)
+///   row_stride   : one row of x     (>= column_count * cell_stride)
+///   slice_stride : one z-slice      (>= row_count    * row_stride)
+/// so the byte offset of voxel (cx, ry, sz) is
+///   sz*slice_stride + ry*row_stride + cx*cell_stride
+/// and `data.size()` must be at least `slice_count * slice_stride`.
+///
+/// Voxel (column cx, row ry, slice sz) has its **center** at, in `frame_id`:
+///   origin ∘ ((cx + .5)*cell_size.x, (ry + .5)*cell_size.y, (sz + .5)*cell_size.z)
+/// where `origin` is the grid's lower-front-left corner (the (0,0,0) corner).
+///
+/// Unlike the 2D OccupancyGrid (which fixes -1/0..100 occupancy semantics), the
+/// per-voxel value is **generic**: `fields` declares the layout (occupancy byte,
+/// RGBA, a float cost/intensity, class id, …) and the renderer decides which
+/// voxels are drawn (the draw predicate / colormap is viewer-side), so one type
+/// serves occupancy maps, costmaps, ESDFs, and semantic grids.
+///
+/// `anchor` keeps the underlying buffer alive — the producer may have made
+/// `data` a view into the source payload (zero-copy) or into a freshly
+/// allocated vector; consumers don't need to know which.
+struct VoxelGrid {
+  Timestamp timestamp_ns = 0;
+  std::string frame_id;       ///< Source coordinate frame; required for 3D TF resolution.
+  Pose origin;                ///< Lower-front-left (0,0,0) corner of the grid in `frame_id`.
+  Vector3 cell_size;          ///< Metric voxel size along x, y, z (meters); need not be cubic.
+  uint32_t column_count = 0;  ///< Voxels along x (fastest-varying).
+  uint32_t row_count = 0;     ///< Voxels along y.
+  uint32_t slice_count = 0;   ///< Voxels along z (depth).
+  uint32_t cell_stride = 0;   ///< Bytes per voxel.
+  uint32_t row_stride = 0;    ///< Bytes per row of x.
+  uint32_t slice_stride = 0;  ///< Bytes per z-slice.
+  std::vector<PointField> fields;
+  Span<const uint8_t> data;
+  BufferAnchor anchor;
+};
+
+}  // namespace sdk
+}  // namespace PJ

pj_base/include/pj_base/builtin/voxel_grid_codec.hpp

@@ -0,0 +1,25 @@
+#pragma once
+// Copyright 2026 Davide Faconti
+// SPDX-License-Identifier: Apache-2.0
+
+#include <cstddef>
+#include <cstdint>
+#include <string_view>
+#include <vector>
+
+#include "pj_base/builtin/voxel_grid.hpp"
+#include "pj_base/expected.hpp"
+
+namespace PJ {
+
+inline constexpr std::string_view kSchemaVoxelGrid = "PJ.VoxelGrid";
+
+/// Serializes sdk::VoxelGrid to canonical PJ.VoxelGrid wire bytes
+/// (see pj_base/proto/pj/VoxelGrid.proto).
+[[nodiscard]] std::vector<uint8_t> serializeVoxelGrid(const sdk::VoxelGrid& grid);
+
+/// Decodes canonical PJ.VoxelGrid wire bytes. The returned object owns its
+/// voxel bytes via `anchor`.
+[[nodiscard]] Expected<sdk::VoxelGrid> deserializeVoxelGrid(const uint8_t* data, size_t size);
+
+}  // namespace PJ

pj_base/include/pj_base/builtin_object_abi.h

@@ -57,6 +57,7 @@ typedef enum PJ_builtin_object_type_t {
   PJ_BUILTIN_OBJECT_TYPE_OCCUPANCY_GRID_UPDATE = 15,
   PJ_BUILTIN_OBJECT_TYPE_LOG = 16,
   PJ_BUILTIN_OBJECT_TYPE_POSES_IN_FRAME = 17,
+  PJ_BUILTIN_OBJECT_TYPE_VOXEL_GRID = 18,
   /* Reserve future types; appended at the tail. Numeric values are stable
    * across releases — never renumber. Each new value here must match the
    * matching kFoo entry in BuiltinObjectType (builtin_object.hpp). */