Visualization Library v1.0.3A lightweight C++ OpenGL middleware for 2D/3D graphics |
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This tutorial demonstrates how to improve the perception of the objects in a scene and how to perform hidden line removal wireframe rendering using the edge extraction and enhnacement capabilities of Visualization Library.
Edge Rendering Off | Silhouettes | Silhouettes + Creases | Silhouettes + Creases + Hidden Lines |
Cartoonish models with silhouette enhancement | |||
Hidden line removal wireframe | |||
In this tutorial we will implement a simple application capable of loading models by drag&drop and applying edge enhancement and hidden line removal wireframe rendering to the whole scene. The user will also be able to interactively switch on and off various edge rendering features:
Key | Mode |
---|---|
'1' | edge rendering off |
'2' | edge rendering on: silhouette only |
'3' | edge rendering on: silhouette + creases |
'4' | edge rendering on: silhouette + creases + hidden lines |
'5' | hidden line removal wireframe: silhouette + creases |
'6' | hidden line removal wireframe: silhouette + creases + hidden lines |
The edges are always extracted from the triangles or quads that are part of a vl::Geometry and can be of three types: silhouette edges, crease edges and boundary edges.
For more information see also vl::EdgeExtractor and vl::EdgeRenderer.
[From App_EdgeRendering.cpp
]
class App_EdgeRendering: public BaseDemo { public: virtual String appletInfo() { return BaseDemo::appletInfo() + "- '1' = edge rendering off.\n" + "- '2' = edge rendering on: silhouette only.\n" + "- '3' = edge rendering on: silhouette + creases.\n" + "- '4' = edge rendering on: silhouette + creases + hidden lines.\n" + "- '5' = edges only: silhouette + creases.\n" + "- '6' = edges only: silhouette + creases + hidden lines.\n" + "\n"; } void initEvent() { vl::Log::notify(appletInfo()); // retrieve the default rendering mMainRendering = rendering()->as<Rendering>(); // retrieve the default renderer, which we'll use as the solid-renderer mSolidRenderer = mMainRendering->renderer(); // create our EdgeRenderer mEdgeRenderer = new EdgeRenderer; // we set the clear flags to be CF_CLEAR_DEPTH (by default is set to CF_CLEAR_COLOR_DEPTH) because // when the wireframe rendering starts we want to preserve the color-buffer as generated by the solid // rendering but we want to clear the Z-buffer as it is needed by the hidden-line-removal algorithm // implemented by EdgeRenderer. mEdgeRenderer->setClearFlags(CF_CLEAR_DEPTH); // target the same opengl window mEdgeRenderer->setFramebuffer(mSolidRenderer->framebuffer()); // enqueue the EdgeRenderer in the rendering, will be executed after mSolidRenderer mMainRendering->renderers().push_back( mEdgeRenderer.get() ); // hidden line and crease options mEdgeRenderer->setShowHiddenLines(true); mEdgeRenderer->setShowCreases(true); mEdgeRenderer->setCreaseAngle(35.0f); // style options mEdgeRenderer->setLineWidth(2.0f); mEdgeRenderer->setSmoothLines(true); mEdgeRenderer->setDefaultLineColor(black); // fills the scene with a few actors. // the beauty of this system is that you setup your actors ony once in a single scene managers and // they will be rendered twice, first using a normal renderer and then using the edge renderer. setupScene(); } // populates the scene void setupScene() { // setup common states ref<Light> camera_light = new Light; ref<EnableSet> enables = new EnableSet; enables->enable(EN_DEPTH_TEST); enables->enable(EN_LIGHTING); // red material fx ref<Effect> red_fx = new Effect; red_fx->shader()->setEnableSet(enables.get()); red_fx->shader()->gocMaterial()->setDiffuse(red); red_fx->shader()->setRenderState(camera_light.get(), 0); // green material fx ref<Effect> green_fx = new Effect; green_fx->shader()->setEnableSet(enables.get()); green_fx->shader()->gocMaterial()->setDiffuse(green); green_fx->shader()->setRenderState(camera_light.get(), 0); // blue material fx ref<Effect> yellow_fx = new Effect; yellow_fx->shader()->setEnableSet(enables.get()); yellow_fx->shader()->gocMaterial()->setDiffuse(yellow); yellow_fx->shader()->setRenderState(camera_light.get(), 0); // add box, cylinder, cone actors to the scene ref<Geometry> geom1 = makeBox (vec3(-7,0,0),5,5,5); ref<Geometry> geom2 = makeCylinder(vec3(0,0,0), 5,5, 10,2, true, true); ref<Geometry> geom3 = makeCone (vec3(+7,0,0),5,5, 20, true); // needed since we enabled the lighting geom1->computeNormals(); geom2->computeNormals(); geom3->computeNormals(); // add the actors to the scene sceneManager()->tree()->addActor( geom1.get(), red_fx.get(), mMainRendering->transform() ); sceneManager()->tree()->addActor( geom2.get(), green_fx.get(), mMainRendering->transform() ); sceneManager()->tree()->addActor( geom3.get(), yellow_fx.get(), mMainRendering->transform() ); } // user controls: // '1' = edge rendering off. // '2' = edge rendering on: silhouette only. // '3' = edge rendering on: silhouette + creases. // '4' = edge rendering on: silhouette + creases + hidden lines. // '5' = edges only: silhouette + creases. // '6' = edges only: silhouette + creases + hidden lines. void keyPressEvent(unsigned short ch, EKey key) { BaseDemo::keyPressEvent(ch, key); if (ch == '1') { mSolidRenderer->setEnableMask(0xFFFFFFFF); mEdgeRenderer->setEnableMask(0); Log::print("Edge rendering disabled.\n"); } else if (ch == '2') { mSolidRenderer->setEnableMask(0xFFFFFFFF); // preserve color buffer, clear depth buffer mEdgeRenderer->setClearFlags(CF_CLEAR_DEPTH); mEdgeRenderer->setEnableMask(0xFFFFFFFF); mEdgeRenderer->setShowCreases(false); mEdgeRenderer->setShowHiddenLines(false); Log::print("Edge rendering enabled. Creases = off, hidden lines = off.\n"); } else if (ch == '3') { mSolidRenderer->setEnableMask(0xFFFFFFFF); // preserve color buffer, clear depth buffer mEdgeRenderer->setClearFlags(CF_CLEAR_DEPTH); mEdgeRenderer->setEnableMask(0xFFFFFFFF); mEdgeRenderer->setShowCreases(true); mEdgeRenderer->setShowHiddenLines(false); Log::print("Edge rendering enabled. Creases = on, hidden lines = off.\n"); } else if (ch == '4') { mSolidRenderer->setEnableMask(0xFFFFFFFF); // preserve color buffer, clear depth buffer mEdgeRenderer->setClearFlags(CF_CLEAR_DEPTH); mEdgeRenderer->setEnableMask(0xFFFFFFFF); mEdgeRenderer->setShowCreases(true); mEdgeRenderer->setShowHiddenLines(true); Log::print("Edge rendering enabled. Creases = on, hidden lines = on.\n"); } else if (ch == '5') { mSolidRenderer->setEnableMask(0); // clear color and depth buffer mEdgeRenderer->setClearFlags(CF_CLEAR_COLOR_DEPTH); mEdgeRenderer->setEnableMask(0xFFFFFFFF); mEdgeRenderer->setShowCreases(true); mEdgeRenderer->setShowHiddenLines(false); Log::print("Hidden line removal wireframe enabled. Creases = on, hidden lines = off.\n"); } if (ch == '6') { mSolidRenderer->setEnableMask(0); // clear color and depth buffer mEdgeRenderer->setClearFlags(CF_CLEAR_COLOR_DEPTH); mEdgeRenderer->setEnableMask(0xFFFFFFFF); mEdgeRenderer->setShowCreases(true); mEdgeRenderer->setShowHiddenLines(true); Log::print("Hidden line removal wireframe enabled. Creases = on, hidden lines = on.\n"); } } void resizeEvent(int w, int h) { Camera* camera = mMainRendering->camera(); camera->viewport()->setWidth ( w ); camera->viewport()->setHeight( h ); camera->setProjectionPerspective(); } void loadModel(const std::vector<String>& files) { // resets the scene sceneManager()->tree()->actors()->clear(); // resets the EdgeRenderer cache mEdgeRenderer->clearCache(); for(unsigned int i=0; i<files.size(); ++i) { ref<ResourceDatabase> resource_db = loadResource(files[i],true); if (!resource_db || resource_db->count<Actor>() == 0) { Log::error("No data found.\n"); continue; } std::vector< ref<Actor> > actors; resource_db->get<Actor>(actors); for(unsigned i=0; i<actors.size(); ++i) { ref<Actor> actor = actors[i].get(); // define a reasonable Shader actor->effect()->shader()->setRenderState( new Light, 0 ); actor->effect()->shader()->enable(EN_DEPTH_TEST); actor->effect()->shader()->enable(EN_LIGHTING); actor->effect()->shader()->gocLightModel()->setTwoSide(true); // add the actor to the scene sceneManager()->tree()->addActor( actor.get() ); } } // position the camera to nicely see the objects in the scene trackball()->adjustView( sceneManager(), vec3(0,0,1)/*direction*/, vec3(0,1,0)/*up*/, 1.0f/*bias*/ ); } // laod the files dropped in the window void fileDroppedEvent(const std::vector<String>& files) { loadModel(files); } protected: ref< Renderer > mSolidRenderer; ref< EdgeRenderer > mEdgeRenderer; ref<Rendering> mMainRendering; }; // Have fun!