Build and Develop ForcePAD

ForcePAD is a C++ application built with CMake and managed dependencies via vcpkg. The primary UI target is qtforcepad (Qt6).

Prerequisites

CMake 3.24 or higher — cmake.org
C++ compiler with C++17 support
Windows: Visual Studio 2022 (with Desktop C++ workload)
Git — git-scm.com
vcpkg — see below

vcpkg setup

ForcePAD uses vcpkg for dependency management. CMake auto-detects vcpkg in the following locations:

VCPKG_ROOT environment variable
E:/vcpkg
C:/vcpkg

If vcpkg is not installed:

git clone https://github.com/Microsoft/vcpkg.git C:/vcpkg
C:/vcpkg/bootstrap-vcpkg.bat
$env:VCPKG_ROOT = "C:/vcpkg"

Building

Default build (Qt6)

cmake -B build-debug
cmake --build build-debug --config Debug

The executable is placed in bin/Debug/qtforcepad.exe.

Force-rebuild a single target

If you change CMakeLists.txt or need the post-build steps to re-run (e.g., Qt plugin deployment):

cmake --build build-debug --config Debug --clean-first --target qtforcepad

Release build

cmake -B build-release
cmake --build build-release --config Release

Executables land in bin/Release/.

Qt runtime deployment (Windows)

The post-build step in src/qtforcepad/CMakeLists.txt automatically copies the required Qt plugin directories (platforms/, styles/) and Qt6Svgd.dll next to the executable. If Qt plugins are missing after a build, the target was likely already up-to-date and MSBuild skipped the post-build step — use --clean-first to force it to re-run.

Architecture overview

Core libraries (shared)

Library	Location	Description
`common`	`src/common/`	FEM data model: `FemGrid2`, `Node`, `Element`, `Force`, `Constraint`, `ColorMap`, etc.
`ivf2d`	`src/ivf2d/`	2D OpenGL rendering primitives
`calfem`	`src/calfem/`	CALFEM C++ port — FEM routines
`fplog`	`src/fplog/`	Logging wrapper (spdlog)

The `fp::PaintView` bridge pattern

fp::PaintView (src/paintview/PaintView.h/cpp) is the ~3600-line core logic class. It owns the FEM grid, brush/drawing state, OpenGL rendering, and event dispatch, and declares virtual methods for all UI interactions:

virtual int height(); virtual int width();
virtual void doRedraw(); virtual void doMakeCurrent();
virtual const std::string doSaveDialog(...);
virtual bool doNewModel(int &w, int &h, int &initialStiffness);

The Qt6 port provides a concrete subclass that inherits from both the framework widget and fp::PaintView:

Qt6: QtPaintView : public QOpenGLWidget, public fp::PaintView (src/qtforcepad/QtPaintView.h)

FEM solver

fp::FemGridSolver2 (src/common/FemGridSolver2.h/cpp) assembles and solves the 2D plane-stress FEM problem and runs topology optimisation. It is compiled directly into each executable (not into the common library) because it calls QCoreApplication::processEvents() to keep the UI responsive during long solves. Do not add it back to the common source glob.

Logging

All logging uses the FPLog wrapper (src/fplog/FPLog.h). Use the fmt-style macros:

#include "FPLog.h"

fp_debug("MyClass", "entering function");
fp_info("MyClass", "loaded {} elements", count);
fp_warn("MyClass", "no boundary conditions found");
fp_error("MyClass", "solver failed: {}", reason);

FPLog::init() wires up sinks at startup. The Qt build adds a QtLogSink (src/qtforcepad/QtLogSink.h) that appends colour-coded messages to the log panel in the main window. Do not include LogWindow.h in any file compiled into the Qt build.

Contributing

Fork the repository on GitHub.
Create a feature branch.
Verify the change builds for the qtforcepad target.
Submit a pull request.