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https://github.com/gha3mi/forcad

ForCAD - A parallel Fortran library for geometric modeling using NURBS
https://github.com/gha3mi/forcad

bezier bsplines cad computer-aided-design curves do-concurrent forcad fortran fortran-package-manager mesh nurbs openmp parallel rational-bezier surfaces volumes vtk

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ForCAD - A parallel Fortran library for geometric modeling using NURBS

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README 

          
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![](logo/logo.png)



**ForCAD**: A parallel Fortran library for geometric modeling using NURBS (Non-Uniform Rational B-Splines).



ForCAD supports **B-Spline**, **NURBS**, **Bezier** and **Rational Bezier** curves, surfaces and volumes.



## Table of Contents

- [Table of Contents](#table-of-contents)

- [Main Features](#main-features)

- [Examples](#examples)

- [Installation](#installation)

  - [Requirements](#requirements)

  - [Clone the repository](#clone-the-repository)

  - [Install PyVista (Optional)](#install-pyvista-optional)

  - [Using fpm](#using-fpm)

    - [Running Examples with fpm](#running-examples-with-fpm)

    - [Using ForCAD as a fpm Dependency](#using-forcad-as-a-fpm-dependency)

  - [Using CMake](#using-cmake)

    - [Install](#install)

    - [Uninstall](#uninstall)

    - [Using ForCAD with CMake](#using-forcad-with-cmake)

- [Configuration](#configuration)

  - [Do Concurrent Support](#do-concurrent-support)

  - [Precision Configuration](#precision-configuration)

- [Dependencies](#dependencies)

- [CI Status](#ci-status)

- [API documentation](#api-documentation)

- [Contributing](#contributing)

- [Citation](#citation)

- [References](#references)



## Main Features



- Parallelized using `do concurrent`.

- Create NURBS objects by specifying control points, weights and knots.

- Refine NURBS objects by inserting or removing knots and elevating degree.

- Compute analytical basis functions and their first and second derivatives for NURBS and B-Spline objects.

- Generation of IGA-compatible element connectivity and shape functions.

- Obtain visualized elements connectivity and coordinates for geometry and control geometry.

- Mesh insertion into a NURBS object.

- Export NURBS objects to VTK files for visualization.

- Export of NURBS curves and surfaces to IGES format (volumes currently not supported).

- Includes predefined NURBS shapes: Circle, Half Circle, Tetragon, Hexahedron, 2D Ring, Half 2D Ring, 3D Ring, Half 3D Ring, C-shapes.

- Rotate and translate NURBS objects.

- Visualization using provided python PyVista scripts.

- Least squares fitting for NURBS curves, surfaces and volumes.

- Numerical integration of: NURBS curve length, NURBS surface area and NURBS volume.



## Examples



Below are some sample outputs from the `examples` directory:



  



  



  



  



  



  



  



## Installation



### Requirements



* Fortran compiler:



  * [GNU Fortran (`gfortran`)](https://gcc.gnu.org/fortran/)

  * [Intel Fortran Compiler (`ifx`)](https://www.intel.com/content/www/us/en/developer/tools/oneapi/hpc-toolkit.html)

  * [NVIDIA HPC SDK Fortran Compiler (`nvfortran`)](https://developer.nvidia.com/hpc-sdk)

  * [LLVM Flang (`flang`)](https://flang.llvm.org/)



  **Note:** Latest compiler versions are required to ensure compatibility.



* Build system:



  * [Fortran Package Manager (`fpm`)](https://fpm.fortran-lang.org/) 

  * [CMake](https://cmake.org/)



* Optional visualization tools:



  * [PyVista](https://pyvista.org/) (recommended)

  * [ParaView](https://www.paraview.org/)



### Clone the repository



Clone the ForCAD repository from GitHub:



```shell

git clone https://github.com/gha3mi/forcad.git

cd forcad

```



### Install PyVista (Optional)



To install PyVista, run the following command:



```shell

pip install pyvista

```



By default PyVista visualization is enabled. To disable it, define the preprocessor flag `NOSHOW_PYVISTA` in the `fpm.toml` file or pass it as a compiler flag.



### Using fpm



#### Running Examples with fpm



```shell

fpm run --example  --compiler gfortran --profile release --flag "-ftree-parallelize-loops=8 -march=native"

```

After executing the examples, `.vtk` files will be generated in the `vtk` directory. To visualize these files, a `show()` method is provided which utilizes PyVista. Alternatively, other visualization tools like ParaView can also be used.



#### Using ForCAD as a fpm Dependency



If you want to use ForCAD as a dependency in your own fpm project,

you can easily include it by adding the following line to your `fpm.toml` file:



```toml

[dependencies]

forcad = {git="https://github.com/gha3mi/forcad.git"}

```



### Using CMake



#### Install



```shell

cmake -S . -B build/cmake -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON -DCMAKE_INSTALL_PREFIX=. -G Ninja

cmake --build build/cmake --config Release

cmake --install build/cmake --config Release --verbose

```



#### Uninstall



```shell

cmake --build build/cmake --target uninstall

```



#### Using ForCAD with CMake



```cmake

find_package(forcad REQUIRED)

add_executable(app main.f90)

target_link_libraries(app PRIVATE forcad::forcad)

```



## Configuration



### Do Concurrent Support



Compiler flags for enabling `do concurrent` parallelism:



| Compiler      | Flag(s)                                             |

| ------------- | --------------------------------------------------- |

| `gfortran`    | `-fopenmp -ftree-parallelize-loops=n`               |

| `ifx`         | `-qopenmp -fopenmp-target-do-concurrent`            |

| `nvfortran`   | `-stdpar=multicore,gpu -Minfo=stdpar,accel`         |

| `flang(-new)` | `-fopenmp -fdo-concurrent-to-openmp=[host\|device]` |

| `lfortran`    | ?                                                   |



*flang-new 21.1.0: warning: Mapping `do concurrent` to OpenMP is still experimental.*



Compiler flags can be passed to fpm using the `--flag` option, for example:



```shell

fpm build --flag "-stdpar=multicore,gpu -Minfo=stdpar,accel"

```



Alternatively, flags can be added to a `fpm.rsp` file in the root directory of the project.



### Precision Configuration



The library uses **double precision** (`real64`) by default for all real-valued computations. To change the precision, you can define one of the following preprocessor flags during compilation:



| Preprocessor Flag    | Fortran Kind             | Description               |

| -------------------- | ------------------------ | ------------------------- |

| `REAL32`             | `selected_real_kind(6)`  | Single precision          |

| `REAL64` *(default)* | `selected_real_kind(15)` | Double precision          |

| `REALXDP`            | `selected_real_kind(18)` | Extended double precision |

| `REAL128`            | `selected_real_kind(33)` | Quadruple precision       |



**Note**: The examples `example_ppm1.f90`, `example_ppm2.f90` and `example_ppm3.f90` use the `ForColormap` library, which only supports `REAL64` precision.



Example: Building with double precision



```bash

fpm build --profile release --flag "-DREAL64"

```



## Dependencies



```mermaid

flowchart LR

  N1[forcad]

  N2[forIGES]

  N3[fordebug]

  N4[forunittest]

  N5[forimage]

  N6[forcolormap]

  N7[fortime]

  N8[FACE]



  click N1 href "https://github.com/gha3mi/forcad" "A parallel Fortran library for geometric modeling using NURBS"

  click N2 href "https://github.com/rweed/forIGES" "Modern Fortran Library for Reading and Writing IGES CAD Files"

  click N3 href "https://github.com/gha3mi/fordebug" "A Fortran library for handling errors, warnings and info messages with debugging support in pure procedures"

  click N4 href "https://github.com/gha3mi/forunittest" "A Fortran library for unit testing"

  click N5 href "https://github.com/gha3mi/forimage" "A Fortran library for processing and editing images and managing colors"

  click N6 href "https://github.com/vmagnin/forcolormap" "A Fortran colormap library"

  click N7 href "https://github.com/gha3mi/fortime" "A Fortran library for measuring elapsed time, DATE_AND_TIME time, CPU time, OMP time and MPI time"

  click N8 href "https://github.com/szaghi/FACE" "Fortran Ansi Colors (and Styles) Environment"



  %% core dependencies

  N1 --> N2

  N1 --> N3

  N3 --> N7

  N7 --> N8



  %% example dependency (dashed line)

  N1 -.->|example| N6

  N6 --> N5



  %% test dependency (dotted line)

  N1 ...->|test| N4

  N4 --> N8

```

Graph generated with [fpm-deps](https://github.com/ivan-pi/fpm-deps), modified to include example and test dependencies.



## CI Status



| Compiler   | macos | ubuntu | windows |

|------------|----------------------|----------------------|----------------------|

| `flang-new` | - | fpm ✅  cmake ✅ | fpm ✅  cmake ✅ |

| `gfortran` | fpm ✅  cmake ✅ | fpm ✅  cmake ✅ | fpm ✅  cmake ✅ |

| `ifx` | - | fpm ✅  cmake ✅ | fpm ✅  cmake ✅ |

| `nvfortran` | - | fpm ✅  cmake ✅ | - |



This table is automatically generated by the CI workflow using [setup-fortran-conda](https://github.com/gha3mi/setup-fortran-conda).



## API documentation



The most up-to-date API documentation for the master branch is available

[here](https://gha3mi.github.io/forcad/).

To generate the API documentation for ForCAD using

[ford](https://github.com/Fortran-FOSS-Programmers/ford) run the following

command:



```shell

ford README.md

```



## Contributing



To contribute to ForCAD, please review the [CONTRIBUTING.md](https://github.com/gha3mi/forcad/blob/main/CONTRIBUTING.md).



## Citation



If you use ForCAD in your research, please cite it as follows:



```bibtex

@software{seyed_ali_ghasemi_2025_10904447,

  author       = {Ghasemi, S. A.},

  title        = {gha3mi/ForCAD},

  year         = {2025},

  publisher    = {Zenodo},

  doi          = {10.5281/zenodo.10904447},

  url          = {https://doi.org/10.5281/zenodo.10904447}

}

```



## References



- Piegl, L., & Tiller, W. (1995). The NURBS Book. In Monographs in Visual Communications. Springer Berlin Heidelberg. [https://doi.org/10.1007/978-3-642-97385-7](https://doi.org/10.1007/978-3-642-97385-7)



- An Introduction to NURBS. (2001). Elsevier. [https://doi.org/10.1016/b978-1-55860-669-2.x5000-3](https://doi.org/10.1016/b978-1-55860-669-2.x5000-3)



- Sullivan et al., (2019). PyVista: 3D plotting and mesh analysis through a streamlined interface for the Visualization Toolkit (VTK). Journal of Open Source Software, 4(37), 1450, https://doi.org/10.21105/joss.01450



- Ahrens, James, Geveci, Berk, Law, Charles, ParaView: An End-User Tool for Large Data Visualization, Visualization Handbook, Elsevier, 2005, ISBN-13: 9780123875822