Custom shaders

This example shows how use custom shaders in gz-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.

Install prerequisites

In order to compile the example in this tutorial, make sure to install the dependencies listed in the Installation tutorial.

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/gazebosim/gz-rendering
cd gz-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(GZ_PI / 4, 0, GZ_PI / 3);
  box->SetLocalScale(1, 2.5, 1);
  box->SetMaterial(shader);