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.cpp]

class App_GLSL: public BaseDemo
{
public:
  App_GLSL()
  {
  }

  void initEvent()
  {
    if (!Has_GLSL)
    {
      Log::error("OpenGL Shading Language not supported.\n");
      Time::sleep(2000);
      exit(1);
    }

    trackball()->setPivot(vl::vec3(4.5f, 4.5f, 0.0f));

    Log::notify(appletInfo());

    ref<ResourceDatabase> res_db = loadResource("/models/3ds/monkey.3ds");
    mModel = res_db->get<Geometry>(0);
    mModel->computeNormals();
    AABB aabb = mModel->boundingBox();
    mModel->transform( mat4::getTranslation(-aabb.center()) );

    ref<Light> light = new Light;

    ref<GLSLProgram> glsl;

    ref<GLSLVertexShader> perpixellight_vs = new GLSLVertexShader("/glsl/perpixellight.vs");

    //glsl = new GLSLProgram;
    //mGLSL.push_back(glsl);
    //glsl->attachShader( perpixellight_vs.get() );
    //glsl->attachShader( new GLSLFragmentShader("/glsl/perpixellight.fs") );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( new GLSLVertexShader("/glsl/examples/toyball.vs") );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/toyball.fs") );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( perpixellight_vs.get() );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/perpixellight_toon.fs") );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( perpixellight_vs.get() );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/heat.fs") );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( perpixellight_vs.get() );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/perpixellight_interlaced.fs") );

    ref<GLSLVertexShader>   noise_vs   = new GLSLVertexShader("/glsl/examples/noise.vs");
    ref<GLSLFragmentShader> noise3D_fs = new GLSLFragmentShader("/glsl/noise3D.glsl");

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( noise_vs.get() );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/alien.fs") );
    glsl->attachShader( noise3D_fs.get() );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( noise_vs.get() );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/cloud.fs") );
    glsl->attachShader( noise3D_fs.get() );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( noise_vs.get() );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/granite.fs") );
    glsl->attachShader( noise3D_fs.get() );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( noise_vs.get() );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/marble.fs") );
    glsl->attachShader( noise3D_fs.get() );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( noise_vs.get() );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/marble2.fs") );
    glsl->attachShader( noise3D_fs.get() );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( noise_vs.get() );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/turbulence.fs") );
    glsl->attachShader( noise3D_fs.get() );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( noise_vs.get() );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/woody.fs") );
    glsl->attachShader( noise3D_fs.get() );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( noise_vs.get() );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/ribbon.fs") );
    glsl->attachShader( noise3D_fs.get() );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( new GLSLVertexShader("/glsl/examples/noisebump.vs") );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/noisebump.fs") );
    glsl->attachShader( noise3D_fs.get() );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( new GLSLVertexShader("/glsl/examples/hatching.vs") );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/hatching.fs") );

    glsl = new GLSLProgram;
    mGLSL.push_back(glsl);
    glsl->attachShader( new GLSLVertexShader("/glsl/examples/stripes.vs") );
    glsl->attachShader( new GLSLFragmentShader("/glsl/examples/stripes.fs") );

    if (Has_Geometry_Shader)
    {
      glsl = new GLSLProgram;
      mGLSL.push_back(glsl);
      // a vertex shader is always needed when using geometry shaders
      glsl->attachShader( new GLSLVertexShader("/glsl/examples/diffuse.vs") );
      glsl->attachShader( new GLSLGeometryShader("/glsl/examples/triangle_fur.gs") );
      glsl->setGeometryInputType(GIT_TRIANGLES);
      glsl->setGeometryOutputType(GOT_TRIANGLE_STRIP);
      glsl->setGeometryVerticesOut( 3*6 );
    }
    else
    {
      Log::print("Geomery shaders not supported.\n");
    }

    mGLSL.resize(4*4);

    for(int y=0; y<4; ++y)
    {
      for(int x=0; x<4; ++x)
      {
        ref<Effect> fx = new Effect;
        fx->shader()->setRenderState( light.get(), 0 );
        fx->shader()->enable(EN_LIGHTING);
        fx->shader()->enable(EN_DEPTH_TEST);
        // fx->shader()->enable(EN_CULL_FACE);
        GLSLProgram* glsl = mGLSL[x + y*4].get();
        if (glsl)
          fx->shader()->setRenderState(glsl);
        ref<Transform> tr = new Transform;
        real grid= 3.0;
        tr->setLocalAndWorldMatrix( mat4::getTranslation(x*grid, y*grid, 0) );
        sceneManager()->tree()->addActor( mModel.get(), fx.get(), tr.get() );
      }
    }
  }

  void fileDroppedEvent(const std::vector<String>& files)
  {
    ref<ResourceDatabase> db = loadResource(files[0]);
    Geometry* geom = db->get<Geometry>(0);
    if (!geom)
      geom = db->get<Actor>(0)->lod(0)->as<Geometry>();
    if (geom)
    {
      mModel->shallowCopyFrom( *geom );
      mModel->computeBounds();
      AABB aabb = mModel->boundingBox();
      real norm = aabb.width() > aabb.height() ? aabb.width() : aabb.height();
      norm = norm > aabb.depth() ? norm : aabb.depth();
      real scale = 1.5;
      mModel->transform( vl::mat4::getTranslation( -aabb.center() ) );
      mModel->transform( vl::mat4::getScaling( scale / norm, scale / norm, scale / norm ) );
    }
  }

  void updateScene()
  {
  }

protected:
  ref<Geometry> mModel;
  std::vector< ref<GLSLProgram> > mGLSL;
};

// Have fun!