OpenGL Shading Language Tutorial

This tutorial shows how simple it is to use the OpenGL Shading Language with Visualization Library.

The example below demostrates the use of vertex shaders, fragment shaders and geometry shaders.

[From App_GLSL.hpp]

class App_GLSL: public BaseDemo
{
public:
  App_GLSL()
  {
    mTransform1 = new vl::Transform;
    mTransform2 = new vl::Transform;
    mTransform3 = new vl::Transform;
    mTransform4 = new vl::Transform;
    mTransform5 = new vl::Transform;
  }

  void initEvent()
  {
    if (!(GLEW_ARB_shading_language_100||GLEW_VERSION_3_0))
    {
      vl::Log::error("OpenGL Shading Language not supported.\n");
      vl::Time::sleep(3000);
      openglContext()->quitApplication();
    }

    BaseDemo::initEvent();

    vl::VisualizationLibrary::rendering()->as<vl::Rendering>()->transform()->addChild(mTransform1.get());
    vl::VisualizationLibrary::rendering()->as<vl::Rendering>()->transform()->addChild(mTransform2.get());
    vl::VisualizationLibrary::rendering()->as<vl::Rendering>()->transform()->addChild(mTransform3.get());
    vl::VisualizationLibrary::rendering()->as<vl::Rendering>()->transform()->addChild(mTransform4.get());
    vl::VisualizationLibrary::rendering()->as<vl::Rendering>()->transform()->addChild(mTransform5.get());

    vl::ref<vl::ResourceDatabase> res_db = vl::loadResource("/models/3ds/monkey.3ds");
    vl::ref<vl::Geometry> model = res_db->get<vl::Geometry>(0);

    vl::ref<vl::Light> light = new vl::Light(0);

    vl::ref<vl::Effect> effect1 = new vl::Effect;
    effect1->shader()->setRenderState( light.get() );
    effect1->shader()->enable(vl::EN_LIGHTING);
    effect1->shader()->enable(vl::EN_DEPTH_TEST);
    effect1->shader()->enable(vl::EN_CULL_FACE);
    sceneManager()->tree()->addActor( model.get(), effect1.get(), mTransform1.get() );

    vl::ref<vl::Effect> effect2 = new vl::Effect;
    effect2->shader()->setRenderState( light.get() );
    effect2->shader()->enable(vl::EN_LIGHTING);
    effect2->shader()->enable(vl::EN_DEPTH_TEST);
    effect2->shader()->enable(vl::EN_CULL_FACE);
    sceneManager()->tree()->addActor( model.get(), effect2.get(), mTransform2.get() );

    vl::ref<vl::Effect> effect3 = new vl::Effect;
    effect3->shader()->setRenderState( light.get() );
    effect3->shader()->enable(vl::EN_LIGHTING);
    effect3->shader()->enable(vl::EN_DEPTH_TEST);
    effect3->shader()->enable(vl::EN_CULL_FACE);
    sceneManager()->tree()->addActor( model.get(), effect3.get(), mTransform3.get() );

    vl::ref<vl::Effect> effect4 = new vl::Effect;
    effect4->shader()->setRenderState( light.get() );
    effect4->shader()->enable(vl::EN_LIGHTING);
    effect4->shader()->enable(vl::EN_DEPTH_TEST);
    effect4->shader()->enable(vl::EN_CULL_FACE);
    sceneManager()->tree()->addActor( model.get(), effect4.get(), mTransform4.get() );

    vl::ref<vl::Effect> effect5 = new vl::Effect;
    effect5->shader()->setRenderState( light.get() );
    effect5->shader()->enable(vl::EN_LIGHTING);
    effect5->shader()->enable(vl::EN_DEPTH_TEST);
    effect5->shader()->enable(vl::EN_CULL_FACE);
    sceneManager()->tree()->addActor( model.get(), effect5.get(), mTransform5.get() );

    if (GLEW_ARB_shading_language_100||GLEW_VERSION_3_0)
    {
      vl::ref<vl::GLSLProgram> glsl;

      glsl = effect1->shader()->gocGLSLProgram();
      glsl->attachShader( new vl::GLSLVertexShader("/glsl/perpixellight.vs") );
      glsl->attachShader( new vl::GLSLFragmentShader("/glsl/perpixellight_cartoon.fs") );

      glsl = effect2->shader()->gocGLSLProgram();
      glsl->attachShader( new vl::GLSLVertexShader("/glsl/perpixellight.vs") );
      glsl->attachShader( new vl::GLSLFragmentShader("/glsl/perpixellight.fs") );

      glsl = effect3->shader()->gocGLSLProgram();
      glsl->attachShader( new vl::GLSLVertexShader("/glsl/perpixellight.vs") );
      glsl->attachShader( new vl::GLSLFragmentShader("/glsl/heat.fs") );

      glsl = effect4->shader()->gocGLSLProgram();
      glsl->attachShader( new vl::GLSLVertexShader("/glsl/perpixellight.vs") );
      glsl->attachShader( new vl::GLSLFragmentShader("/glsl/perpixellight_interlaced.fs") );

      if (GLEW_NV_geometry_shader4 || GLEW_ARB_geometry_shader4 || GLEW_VERSION_3_2)
      {
        glsl = effect5->shader()->gocGLSLProgram();
        // a vertex shader is always needed when using geometry shaders
        glsl->attachShader( new vl::GLSLVertexShader("/glsl/diffuse.vs") );
        glsl->attachShader( new vl::GLSLGeometryShader("/glsl/triangle_fur.gs") );
        glsl->setGeometryInputType(vl::GIT_TRIANGLES);
        glsl->setGeometryOutputType(vl::GOT_TRIANGLE_STRIP);
        glsl->setGeometryVerticesOut( 3*6 );
      }
      else
      {
        effect5->shader()->gocMaterial()->setDiffuse(vlut::red);
        vl::Log::print("GL_NV_geometry_shader4 not supported.\n");
      }
    }
  }

  void run()
  {
    // animate the transforms
    mTransform1->setLocalMatrix( vl::mat4::translation(-2,2,0)  * vl::mat4::rotation( vl::Time::currentTime()*45, 0, 1, 0) );
    mTransform2->setLocalMatrix( vl::mat4::translation(+2,2,0)  * vl::mat4::rotation( vl::Time::currentTime()*45, 0, 1, 0) );
    mTransform3->setLocalMatrix( vl::mat4::translation(-2,-2,0) * vl::mat4::rotation( vl::Time::currentTime()*45, 0, 1, 0) );
    mTransform4->setLocalMatrix( vl::mat4::translation(+2,-2,0) * vl::mat4::rotation( vl::Time::currentTime()*45, 0, 1, 0) );
    mTransform5->setLocalMatrix( vl::mat4::translation(0,0,0)   * vl::mat4::rotation( vl::Time::currentTime()*45, 0, 1, 0) );
  }

  void shutdown() {}

protected:
  vl::ref<vl::Transform> mTransform1;
  vl::ref<vl::Transform> mTransform2;
  vl::ref<vl::Transform> mTransform3;
  vl::ref<vl::Transform> mTransform4;
  vl::ref<vl::Transform> mTransform5;
};

// Have fun!