Open3D C++ API Map

Open3D v0.20.0.

This file does not list class members — the installed headers do that, with signatures and Doxygen comments, always matching the binary you link against:

O3D=/path/to/open3d-devel-.../include
grep -n "" "$O3D/open3d/t/geometry/PointCloud.h" | less   # or open it in your editor
grep -rn "VoxelDownSample" "$O3D/open3d/t/geometry/"

What follows is what grep cannot tell you: which namespace and header own a task, which of many similarly-named methods is the right one, what is current versus legacy, and which behaviors will surprise you.

Namespace and Header Routing

You want to…	Namespace	Header
Numeric arrays, devices, linear algebra	open3d::core	open3d/core/Tensor.h, Device.h, Dtype.h
Neighbor search	open3d::core::nns	open3d/core/nns/NearestNeighborSearch.h
Point clouds, meshes, images, ray casting, TSDF	open3d::t::geometry	open3d/t/geometry/PointCloud.h, TriangleMesh.h, RaycastingScene.h, VoxelBlockGrid.h
Read/write geometry and images	open3d::t::io	open3d/t/io/PointCloudIO.h, TriangleMeshIO.h, ImageIO.h
ICP and registration	open3d::t::pipelines::registration	.../registration/Registration.h, Feature.h, TransformationEstimation.h, RobustKernel.h
RGB-D odometry	open3d::t::pipelines::odometry	.../odometry/RGBDOdometry.h
Dense SLAM	open3d::t::pipelines::slam	.../slam/Model.h, Frame.h
Fragment pose refinement	open3d::t::pipelines::slac	.../slac/SLACOptimizer.h, ControlGrid.h
Show something on screen	open3d::visualization	open3d/visualization/utility/Draw.h
Build a custom 3D app	open3d::visualization::gui / ::rendering	.../gui/Application.h, Window.h, SceneWidget.h; .../rendering/Open3DScene.h, MaterialRecord.h
Sample data	open3d::data	open3d/data/Dataset.h
Logging	open3d::utility	open3d/utility/Logging.h
Legacy Eigen equivalents (fallback only)	open3d::geometry, ::io, ::pipelines, ::camera	open3d/geometry/PointCloud.h, etc.

Umbrella header: open3d/Open3D.h — includes everything public.

Task → API

Point clouds

Task	Call
Load / save	t::io::ReadPointCloud, WritePointCloud
Reduce point count	VoxelDownSample (uniform grid, usual choice), UniformDownSample, RandomDownSample, FarthestPointDownSample (best coverage, slowest)
Normals	EstimateNormals, then OrientNormalsToAlignWithDirection / OrientNormalsTowardsCameraLocation / OrientNormalsConsistentTangentPlane
Denoise	RemoveStatisticalOutliers (density-adaptive), RemoveRadiusOutliers, RemoveNonFinitePoints
Take a subset	SelectByIndex, SelectByMask
Find planes / clusters	SegmentPlane, ClusterDBSCAN
Smooth	SmoothMLS, SmoothLaplacian, SmoothTaubin
Move / colorize	Transform, Translate, Rotate, Scale, PaintUniformColor
From RGB-D	CreateFromDepthImage, CreateFromRGBDImage (static)
Back to 2D	ProjectToDepthImage, ProjectToRGBDImage
Compare two clouds	ComputeMetrics (Chamfer, Hausdorff, F-score)
Access attributes	GetPointPositions / SetPointPositions, GetPointAttr("…") / SetPointAttr for custom ones

Meshes

Task	Call
Load / save	t::io::ReadTriangleMesh, WriteTriangleMesh
Primitives	CreateBox, CreateSphere, CreateCylinder, CreateCone, CreateTorus, CreateArrow, CreateCoordinateFrame, CreateText (static)
Normals	ComputeVertexNormals (smooth shading), ComputeTriangleNormals (flat)
Reduce triangles	SimplifyQuadricDecimation
Repair	FillHoles, RemoveNonManifoldEdges, RemoveUnreferencedVertices
CSG	BooleanUnion, BooleanIntersection, BooleanDifference
Cut	ClipPlane (keep a half-space), SlicePlane (cross-section curves)
Mesh → points	SamplePointsUniformly
UVs and textures	ComputeUVAtlas, BakeVertexAttrTextures, BakeTriangleAttrTextures, ProjectImagesToAlbedo
Surface from a point cloud	legacy only — geometry::TriangleMesh::CreateFromPointCloudPoisson / …AlphaShape / …BallPivoting

Registration

Task	Call
Refine a roughly-aligned pair	MultiScaleICP (preferred) or ICP
Pick the error metric	TransformationEstimationPointToPlane (needs normals, converges fastest), …PointToPoint, …ForColoredICP, …Symmetric, …ForDopplerICP
Downweight outliers	RobustKernel with a RobustKernelMethod — L2Loss, L1Loss, HuberLoss, CauchyLoss, GMLoss, TukeyLoss, GeneralizedLoss
Coarse / global alignment	ComputeFPFHFeature + CorrespondencesFromFeatures (Feature.h); full RANSAC/FGR is legacy only
Score an alignment	EvaluateRegistration
Covariance for a pose graph	GetInformationMatrix
Optimize many fragments jointly	legacy only — pipelines::registration::PoseGraph + GlobalOptimization

Reconstruction

Task	Call
Fuse RGB-D frames	t::geometry::VoxelBlockGrid — GetUniqueBlockCoordinates, then Integrate
Get the surface out	ExtractPointCloud, ExtractTriangleMesh
Frame-to-frame camera pose	t::pipelines::odometry::RGBDOdometryMultiScale
Online dense SLAM	t::pipelines::slam::Model + Frame
Refine fragment poses	t::pipelines::slac::RunSLACOptimizerForFragments

Queries and search

Task	Call
k nearest neighbors	core::nns::NearestNeighborSearch — KnnIndex() then KnnSearch
All neighbors within a radius	FixedRadiusIndex(r) then FixedRadiusSearch
A different radius per query	MultiRadiusIndex / MultiRadiusSearch
k neighbors capped by a radius	HybridIndex / HybridSearch
Ray/mesh intersection	RaycastingScene::CastRays
Distance to a surface	ComputeDistance (unsigned), ComputeSignedDistance (signed)
Inside/outside test	ComputeOccupancy
Closest point on a surface	ComputeClosestPoints
Visibility / counting hits	TestOcclusions, CountIntersections, ListIntersections

KDTreeFlann is legacy — always use core::nns instead.

Visualization

Task	Call
Just look at it	visualization::Draw({geometry})
Several named, toggleable objects	visualization::Draw({DrawObject(name, geom, visible), …})
An image file, no window	gui::Application::RenderToImage with a FilamentRenderer + Open3DScene
Custom app with widgets	gui::Application + gui::Window + gui::SceneWidget + rendering::Open3DScene
Control appearance	rendering::MaterialRecord — set .shader to "defaultLit", "defaultUnlit", "normals", "depth", "unlitLine"

Tensor ↔ Legacy

Same class name, different namespace: PointCloud, TriangleMesh, LineSet, Image, RGBDImage, AxisAlignedBoundingBox, OrientedBoundingBox, and the Read* / Write* IO functions (io::X → t::io::X).

Renamed or restructured:

Legacy	Tensor
pipelines::registration::RegistrationICP	t::pipelines::registration::ICP / MultiScaleICP
pipelines::odometry::*	t::pipelines::odometry::*
pipelines::integration::TSDFVolume	t::geometry::VoxelBlockGrid (block-sparse; not drop-in)
geometry::KDTreeFlann + KDTreeSearchParam*	core::nns::NearestNeighborSearch — always migrate
Eigen matrices in public APIs	core::Tensor
visualization::DrawGeometries / Visualizer	visualization::Draw, gui::Application + rendering::Open3DScene, O3DVisualizer

Tensor geometry types provide static FromLegacy(...) and member ToLegacy().

Legacy-only — a fallback here is justified

camera::* · geometry::Octree · geometry::TetraMesh · geometry::HalfEdgeTriangleMesh · pipelines::integration::* · pose graphs and GlobalOptimization · RANSAC and FGR global registration · pipelines::color_map::* · surface reconstruction from point clouds · legacy OpenGL Visualizer subclasses

Tensor-only — no legacy equivalent

core::Tensor and explicit device placement · core::HashMap · core::nns::NearestNeighborSearch · RaycastingScene · VoxelBlockGrid · custom attributes via TensorMap · SLAC and SLAM · Doppler ICP

Non-Obvious Behavior

Things that cost debugging time and are not visible in a signature.

API	What to know
naming	C++ is PascalCase where Python is snake_case; getters are explicit (GetPointPositions() vs. pcd.point["positions"])
dtype constants	Capitalized in C++ (core::Float32); lowercase in Python
Tensor copies	Shallow by default — use Clone() for a deep copy, Contiguous() when a kernel needs contiguous memory
FromLegacy	Defaults to Float32 even though legacy geometry stores double
RemoveStatisticalOutliers	Returns std::tuple<PointCloud, core::Tensor> (cloud + mask), not just a cloud
any registration result	transformation_ is always Float64 on CPU:0, whatever device the inputs were on
ExtractPointCloud / ExtractTriangleMesh	weight_threshold = 3.0f by default — a voxel needs ≥3 observations, so few-frame integrations come back empty
RaycastingScene	CPU and SYCL only, never CUDA; device is a constructor argument. (The class comment in the header still says CPU-only — the binding docs and implementation are correct.)
ComputeSignedDistance	The sign is only meaningful for watertight meshes
FixedRadiusSearch	Ragged output: values plus row-split offsets
EstimateNormals	Orientation is arbitrary; follow with an OrientNormals* call
index tensors	Must be Int64
utility::LogError	[[noreturn]]; throws std::runtime_error. It is the error mechanism, not a print
device mixing	All inputs to a tensor pipeline must share a device; To(device) each one
CreateRaysPinhole	Two overloads — intrinsic/extrinsic matrices, or fov/center/eye/up
data::*	Downloads on first use; requires network access
gui	Application::GetInstance().Initialize() before any window; main thread only
CUDA / SYCL	A property of the binary you downloaded — check core::cuda::IsAvailable() / core::sycl::IsAvailable() at runtime

Sample Data

open3d::data classes download on construction; read GetPath(), GetPaths(), or type-specific accessors (GetDepthPaths(), GetColorPaths()).

Need	Use
A point cloud	PCDPointCloud, PLYPointCloud, EaglePointCloud
A mesh	BunnyMesh, ArmadilloMesh, KnotMesh
Two clouds to register	DemoICPPointClouds, DemoColoredICPPointClouds, DemoFeatureMatchingPointClouds
An RGB-D sequence	SampleRedwoodRGBDImages, SampleFountainRGBDImages, BedroomRGBDImages, LoungeRGBDImages
A textured model	FlightHelmetModel, DamagedHelmetModel, MonkeyModel, CrateModel
A full indoor scene	LivingRoomPointClouds, OfficePointClouds, RedwoodIndoorLivingRoom1/2

Full list: grep -n "^class" "$O3D/open3d/data/Dataset.h"