Extending simple_demo to include render order

examples/simple_demo/Main.cc

@@ -79,14 +79,16 @@ void buildScene(ScenePtr _scene)
   center->SetMaterial(green);
   root->AddChild(center);
 
-
+//! [red material]
   // create red material
   MaterialPtr red = _scene->CreateMaterial();
   red->SetAmbient(0.5, 0.0, 0.0);
   red->SetDiffuse(1.0, 0.0, 0.0);
   red->SetSpecular(0.5, 0.5, 0.5);
   red->SetShininess(50);
   red->SetReflectivity(0);
+  red->SetRenderOrder(3);
+//! [red material]
 
   // create sphere visual
   VisualPtr sphere = _scene->CreateVisual();
@@ -116,12 +118,15 @@ void buildScene(ScenePtr _scene)
   box->SetMaterial(blue);
   root->AddChild(box);
 
+//! [white material]
   // create white material
   MaterialPtr white = _scene->CreateMaterial();
   white->SetAmbient(0.5, 0.5, 0.5);
   white->SetDiffuse(0.8, 0.8, 0.8);
   white->SetReceiveShadows(true);
   white->SetReflectivity(0);
+  white->SetRenderOrder(0);
+//! [white material]
 
   // create plane visual
   VisualPtr plane = _scene->CreateVisual();
@@ -131,6 +136,15 @@ void buildScene(ScenePtr _scene)
   plane->SetMaterial(white);
   root->AddChild(plane);
 
+  // create plane visual
+  VisualPtr plane2 = _scene->CreateVisual();
+  plane2->AddGeometry(_scene->CreatePlane());
+  plane2->SetLocalScale(5, 8, 1);
+  plane2->SetLocalPosition(4, 0.5, -0.5);
+  plane2->Scale(0.1, 0.1, 1);
+  plane2->SetMaterial(red);
+  root->AddChild(plane2);
+
   // create axis visual
   VisualPtr axis = _scene->CreateAxisVisual();
   axis->SetLocalPosition(4.0, 0.5, -0.4);

include/ignition/rendering/MeshDescriptor.hh

@@ -65,12 +65,16 @@ namespace ignition
       public: const common::Mesh *mesh = nullptr;
       IGN_COMMON_WARN_RESUME__DLL_INTERFACE_MISSING
 
+      IGN_COMMON_WARN_IGNORE__DLL_INTERFACE_MISSING
       /// \brief Name of the registered Mesh
       public: std::string meshName;
+      IGN_COMMON_WARN_RESUME__DLL_INTERFACE_MISSING
 
+      IGN_COMMON_WARN_IGNORE__DLL_INTERFACE_MISSING
       /// \brief Name of the sub-mesh to be loaded. An empty string signifies
       /// all sub-meshes should be loaded.
       public: std::string subMeshName;
+      IGN_COMMON_WARN_RESUME__DLL_INTERFACE_MISSING
 
       /// \brief Denotes if the loaded sub-mesh vertices should be centered
       public: bool centerSubMesh = false;

ogre2/src/Ogre2Material.cc

@@ -154,8 +154,8 @@ void Ogre2Material::SetAlphaFromTexture(bool _enabled,
   Ogre::HlmsBlendblock block;
   if (_enabled)
   {
-    block.setBlendType(Ogre::SBT_TRANSPARENT_ALPHA);
     this->ogreDatablock->setAlphaTest(Ogre::CMPF_GREATER_EQUAL);
+    block.setBlendType(Ogre::SBT_TRANSPARENT_ALPHA);
     this->ogreDatablock->setBlendblock(block);
   }
   else

tutorials/21_render_order.md

@@ -0,0 +1,52 @@
+\page render_order Render order
+
+This example shows how to set the render order for coplanar poligons.
+
+The material API allows changing the render order. When polygons are coplanar, you can get problems
+with `depth fighting` where the pixels from the two polys compete for the same screen pixel. As you
+can see in the following image:
+
+@image html img/render_order_bad.png
+
+The method `SetRenderOrder` in the Material class allows avoiding this issue. The higher value will
+be rendered on top of other coplanar polygons.
+
+In the `simple_demo` example you can find two materials with different render orders. The red material
+(`SetRenderOrder(3)`) has a higher value than the white material (`SetRenderOrder(3)`).
+
+\snippet examples/render_pass/Main.cc red material
+
+\snippet examples/simple_demo/Main.cc white material
+
+As you can see in the following image the z-fighting issue is resolved.
+
+@image html img/render_order_good.png
+
+You can set this in your SDF file including in the material tag a new tag called `render_order` with
+a float value:
+
+```xml
+<material>
+  <render_order>5</render_order>
+  <ambient>0 0 1 1</ambient>
+  <diffuse>0 0 1 1</diffuse>
+  <specular>0 0 1 1</specular>
+</material>
+```
+
+Clone the source code, create a build directory and use `cmake` and `make` to compile the code:
+
+```{.sh}
+git clone https://github.com/ignitionrobotics/ign-rendering
+cd ign-rendering/examples/simple_demo
+mkdir build
+cd build
+cmake ..
+make
+```
+
+Execute the example:
+
+```{.sh}
+./simple_demo
+```