[Metal] enable loading of the Metal render system for ogre2

- Add parameter "metal" and a member variable useMetalRenderSystem to Ogre2RenderEngine
- Modify LoadPlugins to load the Metal render system if enabled
- Modify CreateRenderSystem to select the Metal render system
- Modify RegisterHlms to load the Metal resources
- Add missing Metal shaders for the Terra (from Ogre2)
- Add Metal shader for skybox
- Update skybox material to support universal shaders
- Create subdirectories for GLSL and Metal in media/materials/programs and update Ogre2RenderEngine with new resource locations
- Add Metal and unified shaders to each material
- Add placeholders for a number of shaders to prevent compile errors when running examples
- Minor formatting changes to plain_color, point and skybox Metal shaders.
- Port depth_camera_vs and selection_buffer_fs to Metal
- The mouse_picker, ogre2_demo and transform_control demos now work correctly.
- Shader formatting - replace tabs with whitespace
- Port gaussian_noise vertex and pixel shaders from the GLSL counterparts
- The ogre2_demo and render_pass examples now work correctly.
- Port thermal_camera pixel shader
  - Correct error in thermal material script
  - Port thermal_camera pixel shaders from the GLSL counterparts
  - The thermal_camera examples now runs but further requires testing
- Add stubs for the remaining vertex and pixel shaders to port from GLSL
- Port heat_signature pixel shader
- Initial ports of depth_camera and gpu_rays shaders
  - On Metal the compositor in Ogre2GpuRay has a pixel format exception
  - Texture sampling for depth_camera_final_fs.metal is not using the equivalent of OpenGL's texelFetch
- Fix fragment program specifier in gaussian noise material
  - Unified shader had incorrect specifier
- Fix depth camera vertex shader not found in selection buffer material
  - This is the same issue as fixed in gazebosim#456
- Switch to user RGBA format for internal textures in gpu ray sensor
- Complete port of gpu rays 1st pass shader
  - Complete port of the GPU Rays shader
  - This depends upon the pixel format fix in gazebosim#468
- Add a method to render targets and cameras to retrieve the Metal texture id
  - These functions provide the Metal equivalent of GLId() and RenderTextureGLId() for OpenGL.
  - The argument is the address of a pointer to void* as the object required for Metal is an objective-c type id<MTLTexture> which we do not want exposed in the interface
  - There is a runtime dependency on an upstream change to ogre-next: OGRECave/ogre-next@3b11873
  - cherry-pick 8fc230c
- Ensure line length limits are adhered to.
- Fix inconsistent parameter name in RenderTextureMetalId
  - Fix an inconsistent parameter name causing a CI failure.
- Fix unused parameter warning in RenderTextureMetalId
  - Fix an unused parameter warning causing a CI failure.

Signed-off-by: Rhys Mainwaring <[email protected]>

ogre2/include/ignition/rendering/ogre2/Ogre2RenderEngine.hh

@@ -247,6 +247,9 @@ namespace ignition
       /// \brief True to use the current opengl context
       private: bool useCurrentGLContext = false;
 
+      /// \brief True to use the Metal render system
+      private: bool useMetalRenderSystem = false;
+
       /// \brief Pointer to private data
       private: std::unique_ptr<Ogre2RenderEnginePrivate> dataPtr;
 

ogre2/src/Ogre2RenderEngine.cc

@@ -391,7 +391,7 @@ void Ogre2RenderEngine::CreateLogger()
 
   // create actual log
   this->ogreLogManager = new Ogre::LogManager();
-  this->ogreLogManager->createLog(logPath, true, false, false);
+  this->ogreLogManager->createLog(logPath, true, true, false);
 }
 
 //////////////////////////////////////////////////

ogre2/src/media/materials/programs/Metal/depth_camera_fs.metal

@@ -14,7 +14,6 @@
  * limitations under the License.
  *
  */
-
 // For details and documentation see: depth_camera_fs.glsl
 
 #include <metal_stdlib>

ogre2/src/media/materials/programs/Metal/point_fs.metal

@@ -14,7 +14,6 @@
  * limitations under the License.
  *
  */
-
 #include <metal_stdlib>
 using namespace metal;
 

ogre2/src/media/materials/programs/Metal/point_vs.metal

@@ -14,7 +14,6 @@
  * limitations under the License.
  *
  */
-
 #include <metal_stdlib>
 using namespace metal;