update build documentation

BUILD.md

@@ -1,7 +1,71 @@
-# How to build mGear
+# How to Build mGear Solvers
 
-we are using now CMAKE, this file needs to be updated.
+## Prerequisites
+Before compiling mGear solvers, ensure you have the following installed:
 
+- **CMake** (latest version recommended)
+- **Compiler**
+  - Windows: Microsoft Visual Studio
+  - Linux: GCC / Clang
+  - macOS: Xcode
+- **Maya Development Kit** (Maya SDK) for the respective version
+- **C++ Build Tools**
+- **CMake Generator** matching your platform
+- Execute the following commands from the cmake folder where FindMaya.cmake is
 
+## Windows
+To generate the build solution for Visual Studio, run the following commands:
 
+```sh
+cmake -G "Visual Studio 16 2019" -A x64 -DMAYA_VERSION=2024 ../
+cmake -G "Visual Studio 16 2019" -A x64 -DMAYA_VERSION=2025 ../
+cmake -G "Visual Studio 17 2022" -A x64 -DMAYA_VERSION=2025 ../
+```
+
+To compile the solution:
+```sh
+cmake --build . --config Release
+```
+
+## Linux
+For Linux, use Unix Makefiles as the generator:
+
+```sh
+cmake -G "Unix Makefiles" -DMAYA_VERSION=2025 ../
+cmake --build . --config Release
+```
+
+## macOS
+Use Xcode as the generator and specify the architecture:
+
+```sh
+cmake -G "Xcode" -DMAYA_VERSION=2024 -DCMAKE_OSX_ARCHITECTURES="x86_64;arm64" ../
+cmake -G "Xcode" -DMAYA_VERSION=2025 -DCMAKE_OSX_ARCHITECTURES="x86_64;arm64" ../
+```
+
+If the compiler is not found, reset Xcode tools:
+```sh
+sudo xcode-select --reset
+```
+
+For Maya 2024 and later, you should compile a universal binary:
+```sh
+cmake -G "Xcode" -DMAYA_VERSION=2024 \
+  -DCMAKE_OSX_ARCHITECTURES="x86_64;arm64" \
+  -DMaya_DIR=/Applications/Autodesk/maya2024/Maya.app/Contents/ ../
+
+cmake -G "Xcode" -DMAYA_VERSION=2025 \
+  -DCMAKE_OSX_ARCHITECTURES="x86_64;arm64" \
+  -DMaya_DIR=/Applications/Autodesk/maya2025/Maya.app/Contents/ ../
+```
+
+### Checking Architecture
+To verify that the compiled binary supports both architectures:
+```sh
+lipo -info mgear_solvers.bundle
+```
+
+## Additional Resources
+- [Maya 2024 API Update Guide](https://around-the-corner.typepad.com/adn/2023/03/maya-2024-api-update-guide.html)
+- [Maya 2025 API Update Guide](https://around-the-corner.typepad.com/adn/2024/03/maya-2025-api-update-guide.html)