Fix pattern preset to be loaded using env variable (#13)

* Locate presets with environment variable

* Move presets

* Update README

* Update README.md

Co-authored-by: Piotr Rybicki <piotr.rybicki@robotec.ai>

* Revert lidar_patterns name

---------

Co-authored-by: Piotr Rybicki <piotr.rybicki@robotec.ai>

README.md

@@ -19,7 +19,7 @@ Key features:
 
 ## Requirements:
 
-- OS: Linux
+- OS: [Ubuntu 20.04](https://releases.ubuntu.com/focal/) or [Ubuntu 22.04](https://releases.ubuntu.com/jammy/)
 
 - Gazebo: [Fortress 6.14](https://gazebosim.org/docs/fortress/install)
 
@@ -73,6 +73,13 @@ ign gazebo sonoma_with_rgl.sdf
 2. The lidar hits should be visible in the GUI
 3. You can control the car using the Teleop plugin (preferably changing the steering to the keyboard and upping the speed to 15)
 
+The second sample world (rgl_playground.sdf) contains all supported object types with this plugin. Since the pattern_type is configured as `pattern_preset`, it is required to set `RGL_PATTERNS_DIR` environment variable before running the simulation:
+```shell
+# From the top-level directory of this repository
+export RGL_PATTERNS_DIR=`pwd`/lidar_patterns
+ign gazebo test_world/rgl_playground.sdf
+```
+
 ## Using the plugin:
 
 RGLServerPlugin contains two plugins: `RGLServerPluginManager` and `RGLServerPluginInstance`. For the plugin to work properly, we need to include both.
@@ -146,7 +153,7 @@ Inside the link entity in your model, add a custom sensor:
   ```
 
 - **pattern_preset**\
-  You can type in the name of a LiDAR to use its pattern (all available patterns are shown below).
+  We have prepared several lidar presets. You can type in the name of a LiDAR to use its pattern (all available patterns are shown below). 
   ```xml
   <pattern_preset>Alpha Prime</pattern_preset>
   <pattern_preset>Puck</pattern_preset>
@@ -155,6 +162,11 @@ Inside the link entity in your model, add a custom sensor:
   <pattern_preset>Pandar64</pattern_preset>
   <pattern_preset>Pandar40P</pattern_preset>
   ```
+  **Note:** Before launching the simulation it is required to set `RGL_PATTERNS_DIR` environment variable with the path to pattern presets directory (`lidar_patterns` from repository).
+  ```shell
+  # For example
+  export RGL_PATTERNS_DIR=`pwd`/lidar_patterns
+  ```
 
 - **pattern_preset_path**\
   If you wish so, You can create your own preset by providing a binary file with the structure below repeated as many times as you fancy. Please note that an absolute path is required.

RGLServerPlugin/include/LidarPatternLoader.hh

@@ -52,8 +52,6 @@ private:
 
     static std::map<std::string, std::string> presetNameToFilename;
     static std::map<std::string, LoadFuncType> patternLoadFunctions;
-
-    static const std::filesystem::path PRESETS_DIR;
 };
 
 }  // namespace rgl

RGLServerPlugin/src/LidarPatternLoader.cc

@@ -12,16 +12,18 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <cstdlib>
+
 #include "LidarPatternLoader.hh"
 
+#define PATTERNS_DIR_ENV "RGL_PATTERNS_DIR"
+
 using namespace std::placeholders;
 namespace fs = std::filesystem;
 
 namespace rgl
 {
 
-const fs::path LidarPatternLoader::PRESETS_DIR = fs::path(__FILE__).parent_path().parent_path() / "lidar_patterns";
-
 std::map<std::string, std::string> LidarPatternLoader::presetNameToFilename = {
     {"Alpha Prime", "VelodyneVLS128.mat3x4f"},
     {"Puck", "VelodyneVLP16.mat3x4f"},
@@ -186,11 +188,14 @@ bool LidarPatternLoader::LoadPatternFromPreset(const sdf::ElementConstPtr& sdf,
         ignerr << "Failed to load preset pattern. Preset '" << presetName << "' is not available.\n";
         return false;
     }
-    fs::path presetPath = PRESETS_DIR / presetNameToFilename[presetName];
+    fs::path presetPath = presetNameToFilename[presetName];
+    if (const char* presetDir = std::getenv(PATTERNS_DIR_ENV)) {
+        presetPath = fs::path(presetDir) / presetNameToFilename[presetName];
+    }
     ignmsg << "Loading pattern_preset '" << presetName << "'...\n";
     outPattern = LoadVector<rgl_mat3x4f>(presetPath);
     if (outPattern.size() == 0) {
-        ignerr << "Failed to load preset.\n";
+        ignerr << "Failed to load preset. Make sure the environment variable '" << PATTERNS_DIR_ENV << "' is set correctly.\n";
         return false;
     }
     return true;