support different shader param language

Signed-off-by: Ian Chen <[email protected]>

Author: iche033

src/systems/shader_param/ShaderParam.cc

@@ -65,11 +65,21 @@ class ignition::gazebo::systems::ShaderParamPrivate
     public: std::vector<std::string> args;
   };
 
-  /// \brief Path to vertex shader
-  public: std::string vertexShaderUri;
+  /// \brief Data structure for storing shader files uri
+  public: class ShaderUri
+  {
+    /// \brief Shader language: glsl or metal
+    public: std::string language;
+
+    /// \brief Path to vertex shader
+    public: std::string vertexShaderUri;
 
-  /// \brief Path to fragment shader
-  public: std::string fragmentShaderUri;
+    /// \brief Path to fragment shader
+    public: std::string fragmentShaderUri;
+  };
+
+  /// \brief A map of shader language to shader program files
+  public: std::map<std::string, ShaderUri> shaders;
 
   /// \brief Mutex to protect sim time updates.
   public: std::mutex mutex;
@@ -179,9 +189,16 @@ void ShaderParam::Configure(const Entity &_entity,
   }
 
   // parse path to shaders
-  if (sdf->HasElement("shader"))
+  if (!sdf->HasElement("shader"))
+  {
+    ignerr << "Unable to load shader param system. "
+           << "Missing <shader> SDF element." << std::endl;
+    return;
+  }
+  // allow mulitple shader SDF element for different shader languages
+  sdf::ElementPtr shaderElem = sdf->GetElement("shader");
+  while (shaderElem)
   {
-    sdf::ElementPtr shaderElem = sdf->GetElement("shader");
     if (!shaderElem->HasElement("vertex") ||
         !shaderElem->HasElement("fragment"))
     {
@@ -190,16 +207,35 @@ void ShaderParam::Configure(const Entity &_entity,
     }
     else
     {
+      // default to glsl
+      std::string api = "glsl";
+      if (shaderElem->HasAttribute("language"))
+        api = shaderElem->GetAttribute("language")->GetAsString();
+
+      ShaderParamPrivate::ShaderUri shader;
+      shader.language = api;
+
       sdf::ElementPtr vertexElem = shaderElem->GetElement("vertex");
-      this->dataPtr->vertexShaderUri = common::findFile(
+      shader.vertexShaderUri = common::findFile(
           asFullPath(vertexElem->Get<std::string>(),
           this->dataPtr->modelPath));
       sdf::ElementPtr fragmentElem = shaderElem->GetElement("fragment");
-      this->dataPtr->fragmentShaderUri = common::findFile(
+      shader.fragmentShaderUri = common::findFile(
           asFullPath(fragmentElem->Get<std::string>(),
           this->dataPtr->modelPath));
+      this->dataPtr->shaders[api] = shader;
+
+      std::cerr << "api: " << api << ", " << shader.vertexShaderUri << std::endl;
+
+      shaderElem = shaderElem->GetNextElement("shader");
     }
   }
+  if (this->dataPtr->shaders.empty())
+  {
+    ignerr << "Unable to load shader param system. "
+           << "No valid shaders." << std::endl;
+    return;
+  }
 
   this->dataPtr->entity = _entity;
   auto nameComp = _ecm.Component<components::Name>(_entity);
@@ -272,8 +308,30 @@ void ShaderParamPrivate::OnUpdate()
   if (!this->material)
   {
     auto mat = scene->CreateMaterial();
-    mat->SetVertexShader(this->vertexShaderUri);
-    mat->SetFragmentShader(this->fragmentShaderUri);
+
+    // default to glsl
+    auto it = this->shaders.find("glsl");
+    if (it != this->shaders.end())
+    {
+      mat->SetVertexShader(it->second.vertexShaderUri);
+      mat->SetFragmentShader(it->second.fragmentShaderUri);
+    }
+    // prefer metal over glsl on macOS
+    // \todo(anyone) instead of using ifdef to check for macOS,
+    // expose add an accessor function to get the GraphicsApi
+    // from rendering::RenderEngine
+#ifdef __APPLE__
+    auto metalIt = this->shaders.find("metal");
+    if (metalIt != this->shaders.end())
+    {
+      mat->SetVertexShader(metalIt->second.vertexShaderUri);
+      mat->SetFragmentShader(metalIt->second.fragmentShaderUri);
+      // if both glsl and metal are specified, print a msg to inform that
+      // metal is used instead of glsl
+      if (it != this->shaders.end())
+        ignmsg << "Using metal shaders. " << std::endl
+    }
+#endif
     this->visual->SetMaterial(mat);
     scene->DestroyMaterial(mat);
     this->material = this->visual->Material();

src/systems/shader_param/ShaderParam.hh

@@ -37,7 +37,11 @@ namespace systems
   ///
   /// Plugin parameters:
   ///
-  /// <shader>
+  /// <shader>     Shader to use - can be repeated to specify shader programs
+  ///              written in different languages.
+  ///              Attributes:
+  ///                language - Shader language. Possible values: glsl, metal
+  ///                           Default to glsl if not specified
   ///   <vertex>   Path to vertex program
   ///   <fragment> Path to fragment program
   /// <param>      Shader parameter - can be repeated within plugin SDF element
@@ -54,7 +58,7 @@ namespace systems
   /// \verbatim
   ///     <plugin filename="ignition-gazebo-shader-param-system"
   ///             name="ignition::gazebo::systems::ShaderParam">
-  ///        <shader>
+  ///        <shader language='glsl'>
   ///          <vertex>materials/my_vs.glsl</vertex>
   ///          <fragment>materials/my_fs.glsl</fragment>
   ///        </shader>