Custom shaders

This example shows how use custom shaders in ign-rendering to change the appearance of objects in the scene. It demonstrates two uses of shaders: The first is setting shaders for a camera and the other is setting shaders for an object in the scene.

Compile and run the example

Clone the source code, create a build directory and use cmake and make to compile the code:

git clone https://github.com/ignitionrobotics/ign-rendering
cd ign-rendering/examples/custom_shaders
mkdir build
cd build
cmake ..
make

./custom_shaders

You'll see:

Image saved: depth.png
Image saved: regular.png

The depth.png shows result of setting shaders for a camera: This example shades objects in the scene based on their depth values

The regular.png shows result of setting shaders for a visual: This example changes the box visual in the scene to a flat green color

Code

In the first lines of the custom_shaders.cc file there are some constants defined with the name of the shaders that the program will use:

const std::string depth_vertex_shader_file =
  "depth_vertex_shader.glsl";
const std::string depth_fragment_shader_file =
  "depth_fragment_shader.glsl";
const std::string vertex_shader_file = "vertex_shader.glsl";
const std::string fragment_shader_file = "fragment_shader.glsl";

Construct absolute path to the shaders. Here the RESOURCE_PATH variable points to the media directory where the two sets of shaders are located:

  // path to look for vertex and fragment shaders
  std::string depth_vertex_shader_path = gz::common::joinPaths(
      RESOURCE_PATH,  depth_vertex_shader_file);
 
  std::string depth_fragment_shader_path = gz::common::joinPaths(
      RESOURCE_PATH, depth_fragment_shader_file);

The first set of shaders are applied to the camera:

  // create shader material
  gz::rendering::MaterialPtr depthMat = scene->CreateMaterial();
  depthMat->SetVertexShader(depth_vertex_shader_path);
  depthMat->SetFragmentShader(depth_fragment_shader_path);
 
  // apply shader to camera
  depthCamera->SetMaterial(depthMat);

The second set of shaders are applied to the visual's material:

  // create shader material
  gz::rendering::MaterialPtr shader = _scene->CreateMaterial();
  shader->SetVertexShader(vertex_shader_path);
  shader->SetFragmentShader(fragment_shader_path);
 
  // create box visual and apply shader
  gz::rendering::VisualPtr box = _scene->CreateVisual();
  box->AddGeometry(_scene->CreateBox());
  box->SetOrigin(0.0, 0.5, 0.0);
  box->SetLocalPosition(3, 0, 0);
  box->SetLocalRotation(IGN_PI / 4, 0, IGN_PI / 3);
  box->SetLocalScale(1, 2.5, 1);
  box->SetMaterial(shader);