Update integration with external mujoco library

.gitignore

@@ -1,3 +1,4 @@
+build/
 Lingo.lock
 bin
 src-gen

README.md

@@ -6,27 +6,47 @@ The derived reactors customize this base class for particular MuJoCo model files
 
 ## Prerequisites
 
-MuJoCo depends on [GLFW](https://www.glfw.org), a graphics library that you must install.  On macOS:
+### Linux (Ubuntu)
+
+1. Install GLFW, a graphics library used by MuJoCo
+
+```sh
+apt install libglfw3-dev
+```
+
+2. Download a prebuilt version of Mujoco v3.2.6 and install it to `/opt/mujoco`. The following works for x86, for aarch64, change the download path accordingly (https://github.com/google-deepmind/mujoco/releases/tag/3.2.6)
+```sh
+wget https://github.com/google-deepmind/mujoco/releases/download/3.2.6/mujoco-3.2.6-linux-x86_64.tar.gz
+tar xvf mujoco-*
+sudo mv mujoco-3.2.6 /opt/mujoco
+```
+
+Alternatively, Mujoco can be built from source as explained under the section for MacOS below.
+
+### macOS
+1. Install GLFW, a graphics library used by MuJoCo
 
 ```sh
 brew install glfw
 ```
 
-MuJoCo itself seems to be best installed from source.  The following worked for me on macOS:
+2. Build Mujoco v3.2.6 from source and install to `/opt/mujoco`
 
 ```sh
-git clone git@github.com:google-deepmind/mujoco.git
+git clone https://github.com/google-deepmind/mujoco.git -b 3.2.6
 cd mujoco
 mkdir build
 cd build
-cmake .. -DCMAKE_INSTALL_PREFIX=/usr/local
+cmake .. -DCMAKE_INSTALL_PREFIX=/opt/mujoco
 cmake --build .
 sudo cmake --install .
+
 ```
 
-The `sudo` on the last line is required to install it in `/usr/local`, which is what I did.
+### All platforms
 
-The [mujoco.cmake](src/include/mujoco.cmake) file will need to be changed if you change either of the above install locations.
+If mujoco is installed to a different location the
+[mujoco.cmake](src/include/mujoco.cmake) must be updated accordingly.
 
 ## Demos
 

src/MuJoCoCarDemo.lf

@@ -13,7 +13,7 @@ target C {
   keepalive: true, // Because of physical action.
 }
 
-import MuJoCoCar from "lib/MujocoCar.lf"
+import MuJoCoCar from "lib/MuJoCoCar.lf"
 
 main reactor(period: time = 33333333 ns, speed_sensitivity: double = 0.05, turn_sensitivity: double = 0.01) {
   timer t(0, period)

src/include/mujoco.cmake

@@ -1,11 +1,14 @@
 # For Mujoco
-list(APPEND CMAKE_PREFIX_PATH "/usr/local/")
-find_package(mujoco REQUIRED)
-target_include_directories(${LF_MAIN_TARGET} PUBLIC /usr/local/include)
-target_link_libraries(${LF_MAIN_TARGET} PUBLIC mujoco::mujoco)
+# If mujoco is installed to a different location, then the following variable
+# should be set to the correct path. See README.md
+set(MUJOCO_PATH "/opt/mujoco")
+list(APPEND CMAKE_PREFIX_PATH ${MUJOCO_PATH})
+find_library(MUJOCO_LIB mujoco REQUIRED)
+find_path(MUJOCO_INCLUDE_PATH mujoco REQUIRED)
+target_include_directories(${LF_MAIN_TARGET} PUBLIC ${MUJOCO_INCLUDE_PATH})
+target_link_libraries(${LF_MAIN_TARGET} PUBLIC ${MUJOCO_LIB})
 
 # For GLFW
-list(APPEND CMAKE_PREFIX_PATH "/opt/homebrew/")
-find_package(glfw3 3.4 REQUIRED)
-target_include_directories(${LF_MAIN_TARGET} PUBLIC /opt/homebrew/include)
+find_package(glfw3 REQUIRED)
+target_include_directories(${LF_MAIN_TARGET} PUBLIC ${glfw3_INCLUDE_DIRS})
 target_link_libraries(${LF_MAIN_TARGET} PUBLIC glfw)

src/lib/MuJoCoCar.lf

@@ -6,7 +6,7 @@ target C {
   files: "../models/car.xml"
 }
 
-import MuJoCoBase from "MujocoBase.lf"
+import MuJoCoBase from "MuJoCoBase.lf"
 
 /**
  * @brief Model of a two-wheeled steerable vehicle.