# Visualization Library

A lightweight C++ OpenGL middleware for 2D/3D graphics

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# 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!

Visualization Library v2011.09.1162 Reference Documentation
Copyright 2005-2011 Michele Bosi. All rights reserved.
Updated on Thu Jan 26 2012 00:43:55.
Permission is granted to use this page to write and publish articles regarding Visualization Library.