go-topo

Go bindings for a 3D topological geometry modeling library built on OpenCASCADE. Provides a CadQuery-style workplane API for parametric CAD modeling from Go.

go get github.com/flywave/go-topo

Architecture

Go package (package topo)
    ↕ cgo
C API layer  (src/*_c_api.cc → libtopo.a)
    ↕
C++ core     (namespace flywave::topo)
    ↕
OpenCASCADE  (external/ogg/)

Quick Start

package main

import "github.com/flywave/go-topo"

func main() {
    wp := topo.NewWorkplane()
    r := wp.BoxCentered(2.0, 2.0, 0.5)
    r.ExportTo("plate.step")  // → STEP
    r.ExportTo("plate.stl")   // → STL (binary)
}

Key Types

Type	Description
Workplane	Fluent CAD modeling API (100+ methods)
Shape	Generic 3D shape (compound/solid/face/wire/edge/vertex)
Vertex	0D point
Edge	1D curve
Wire	Connected sequence of edges
Face	2D surface
Shell	Connected collection of faces
Solid	Closed 3D volume
Compound	Collection of any shapes
TopoVector	3D vector
TopoLocation	Placement / transformation
Selector	Shape filtering by direction, radius, area, etc.

Workplane API

Construction and sketching is done through the Workplane type:

wp := topo.NewWorkplane()

// 2D sketching
r := wp.CircleCentered(2.0)
r = r.RectCentered(0.5, 0.75)
r = r.PolygonSimple(6, 1.0)

// 3D operations
r = r.ExtrudeSimple(0.5)
r = r.RevolveSimple(180)
r = r.LoftSimple()

// Boolean operations
r = r.Cut(other, true, 0.001)
r = r.Union(other, true, false, 0.001)

// Face/edge selection
r = r.Faces(">Z", "")
r = r.Edges("|Z", "").Fillet(0.125)

// Through-hole
r = r.HoleThrough(diameter)

// Export
r.ExportTo("output.step")
r.ExportTo("output.stl")

Export Formats

Format	Extension	Method
STEP	.step, .stp	ExportTo(path) — auto-detected
STL	.stl	ExportTo(path) — binary, auto-detected
BREP	.brep	Shape.ExportBrep(path)

ExportTo detects format from the file extension.

Import Formats

Format	Entry Point
STEP	Shape.ImportFromStep(path)
BREP	Shape.ImportFromBrep(path)
DXF	NewDxfReader(path) → .DoRead()
IFC	IfcConverter.LoadFile(path)

Directory Structure

go-topo/
├── *.go                  # Go package (package topo)
├── src/                  # C++ source → libtopo.a
│   ├── *.hh, *.cc        # Core C++ geometry kernel
│   ├── *_c_api.cc        # C API bridge layer
│   └── *_test.cc         # C++ tests
├── libs/                 # Prebuilt static libraries
│   ├── linux/            # libtopo.a + OpenCASCADE + deps
│   ├── linux_arm/
│   ├── darwin/
│   ├── darwin_arm/
│   └── windows/
├── external/             # Vendored C++ deps
│   └── ogg/              # OpenCASCADE source
├── go.mod
└── CMakeLists.txt

Building the C++ Library

cmake -S . -B build/build && cmake --build build/build --config Release
cmake --install build/build --prefix libs/linux

Requires prebuilt dependencies in external/. For Apple Silicon:

cmake -S . -B build/build -G "Xcode" && cmake --build build/build --config Release
cmake --install build/build --prefix libs/darwin_arm

Testing

go test ./...              # Requires prebuilt libs in libs/
go test -v -count=1 ./...

Build and run the 33 CadQuery-style example tests:

go test -v -run "Test_example_" .

Dependencies

C++ (vendored): OpenCASCADE, Boost 1.67, Ipopt, Eigen, IFC, fontconfig, freetype, ICU, NLopt, METIS, LAPACK/BLAS, MA27, libxml2, libexpat, zlib, RapidJSON

Go: github.com/flywave/go3d, golang.org/x/image

License

See LICENSE file.