OpenSceneGraph 3.0

Time for action—implementing a cartoon cow

The cartoon shading is a simple non-photorealistic effect which changes abruptly between tones. To archive a cartoon shader, we only have to transform the vertex to built-in gl_Position variables in the vertex shader, and then calculate and select a tone by using the normal and light direction in the fragment shader. After that, we may apply it to a loaded model, for instance, a pretty cow.

1. Include the necessary headers:

   #include <osg/Program>
   #include <osgDB/ReadFile>
   #include <osgViewer/Viewer>
   

2. We'd like to write the vertex shader source using strings. It passes a normal varying variable to the fragment shader, besides setting the gl_Position:

   static const char* vertSource = { "varying vec3 normal;\n" ...