In this tutorial you will learn how to define a set of LOD (level of detail) geometries using the vl::DistanceLODEvaluator class and how to animate your geometry using the vl::ActorEventCallback class.
This demo creates a scene containing a central animated wave geometry and a few objects surrounding it in a circle. The central wave geometry defines 3 level of detail which will be animated in realtime using a subclass of vl::ActorEventCallback created ad-hoc. The surrounding objects are there to demonstrate even more clearly how to use geomety LOD. Each objects is rendered as a sphere at LOD level #0, as a cube at LOD level #1 and as a wireframe pyramid at LOD level #2. Note that the demo also uses the same LOD evaluator to perform Effect lod, demonstrating how simple it is to synchronize geometry and effect LOD.
[From App_GeomLODAnim.cpp]
#include "BaseDemo.hpp" #include <vlCore/Colors.hpp> #include <vlGraphics/GeometryPrimitives.hpp> #include <vlGraphics/DistanceLODEvaluator.hpp> #include <vlGraphics/PixelLODEvaluator.hpp> #include <vlGraphics/Light.hpp> /* Implements an animated wave geometry. */ class WaveActorAnimator: public vl::ActorEventCallback { public: // initialize the 3 gometry LODs and installs them into the specified Actor WaveActorAnimator(vl::Actor* actor) { mLastUpdate = 0; mLastUpdatedLod = NULL; vl::ref<vl::Geometry> geom; const float side = 40; const int detail = 60; // LOD 0 geom = vl::makeGrid( vl::vec3(0,0,0), side, side, detail, detail ); // geom->setColor(vl::royalblue); actor->setLod(0, geom.get()); geom->setBufferObjectEnabled(true); if (vl::Has_GL_ARB_vertex_buffer_object) { geom->vertexArray()->bufferObject()->setBufferData(vl::BU_DYNAMIC_DRAW,false); } // LOD 1 geom = vl::makeGrid( vl::vec3(0,0,0), side, side, detail/2, detail/2 ); // geom->setColor(vl::green); actor->setLod(1, geom.get()); geom->setBufferObjectEnabled(true); if (vl::Has_GL_ARB_vertex_buffer_object) { geom->vertexArray()->bufferObject()->setBufferData(vl::BU_DYNAMIC_DRAW,false); } // LOD 2 geom = vl::makeGrid( vl::vec3(0,0,0), side, side, detail/4, detail/4 ); // geom->setColor(vl::yellow); actor->setLod(2, geom.get()); geom->setBufferObjectEnabled(true); if (vl::Has_GL_ARB_vertex_buffer_object) { geom->vertexArray()->bufferObject()->setBufferData(vl::BU_DYNAMIC_DRAW,false); } } // respond to onActorRenderStarted() event by animating the wave virtual void onActorRenderStarted(vl::Actor*, vl::real frame_clock, const vl::Camera*, vl::Renderable* renderable, const vl::Shader*, int pass) { /* the beauty of this function is that in a few lines of code we update 3 different LOD levels! */ // update the geometry only the first time it is drawn if (pass > 0) return; // clamp animation to 30 FPS const vl::real fps = 30.0f; if ( frame_clock - mLastUpdate > 1.0f/fps || mLastUpdatedLod != renderable ) { mLastUpdate = frame_clock; mLastUpdatedLod = renderable; // note: this returns the current LOD geometry vl::ref<vl::Geometry> geom = vl::cast<vl::Geometry>( renderable ); vl::ref<vl::ArrayFloat3> vecarr3 = vl::cast<vl::ArrayFloat3>( geom->vertexArray() ); vl::fvec3* vec = vecarr3->begin(); vl::vec3 center = renderable->boundingBox().center(); float phi = 0.5; float theta = 1.5; for(size_t i=0; i<vecarr3->size(); ++i) { // flatten to xz plane and compute distance vec[i].y() = 0; vl::real d = (vl::vec3(vec[i])-center).length(); vec[i].y() = (float)cos( -frame_clock * vl::fPi * theta + d * phi ) * 2.0f; } if (vl::Has_GL_ARB_vertex_buffer_object) { geom->vertexArray()->bufferObject()->setBufferData(vl::BU_DYNAMIC_DRAW, false); } // when modifying the vertices of a geometry always remember to update the bounding volumes! geom->setBoundsDirty(true); } } // don't respond to onActorDelete() event. virtual void onActorDelete(vl::Actor*) { } protected: vl::real mLastUpdate; vl::Renderable* mLastUpdatedLod; }; /* This test shows how to enable shader-lod, geometry-lod and how to animate a simple wave geometry over different LODs. */ class App_GeomLODAnim: public BaseDemo { public: void initEvent() { vl::Log::notify(appletInfo()); /* configure how many objects are there forming the ring */ const int ring_obj_count = 20; /* define a LOD evaluator with 3 disance ranges: [0] --- 70 --- 150 --- [inf] */ vl::ref<vl::DistanceLODEvaluator> lod_eval = new vl::DistanceLODEvaluator; lod_eval->distanceRangeSet().push_back(70); lod_eval->distanceRangeSet().push_back(150); /* to be used later */ vl::ref<vl::Light> light = new vl::Light; vl::ref<vl::Shader> wire_sh = new vl::Shader; vl::ref<vl::Shader> fill_sh = new vl::Shader; vl::ref<vl::Shader> wave_sh = new vl::Shader; /* fill pass */ fill_sh->enable(vl::EN_DEPTH_TEST); fill_sh->enable(vl::EN_CULL_FACE); fill_sh->enable(vl::EN_LIGHTING); fill_sh->gocMaterial()->setFrontDiffuse( vl::white ); fill_sh->gocPolygonMode()->set(vl::PM_FILL, vl::PM_FILL); // note this is default fill_sh->setRenderState( light.get(), 0 ); /* wire pass */ wire_sh->enable(vl::EN_DEPTH_TEST); wire_sh->enable(vl::EN_LIGHTING); wire_sh->enable(vl::EN_BLEND); // for line smoothing wire_sh->enable(vl::EN_LINE_SMOOTH); wire_sh->enable(vl::EN_POLYGON_OFFSET_LINE); wire_sh->gocHint()->setLineSmoothHint(vl::HM_NICEST); wire_sh->gocMaterial()->setFlatColor( vl::royalblue ); wire_sh->gocPolygonMode()->set(vl::PM_LINE, vl::PM_LINE); wire_sh->gocPolygonOffset()->set(-1.0f, -1.0f); wire_sh->setRenderState( light.get(), 0 ); /* wave pass */ wave_sh->enable(vl::EN_BLEND); // for line smoothing wave_sh->enable(vl::EN_LINE_SMOOTH); wave_sh->gocHint()->setLineSmoothHint(vl::HM_NICEST); wave_sh->gocPolygonMode()->set(vl::PM_LINE, vl::PM_LINE); /* animated wave actor has a single Effect LOD */ vl::ref<vl::Effect> wave_fx = new vl::Effect; wave_fx->setLOD( 0, wave_sh.get() ); /* add wave actor */ vl::ref<vl::Actor> wave_act = sceneManager()->tree()->addActor(NULL, wave_fx.get(), NULL); /* install actor animation callback. */ wave_act->actorEventCallbacks()->push_back( new WaveActorAnimator(wave_act.get()) ); /* install the LOD evaluator */ wave_act->setLODEvaluator(lod_eval.get()); /* effect used by the objects forming a ring around the central wave */ vl::ref<vl::Effect> ring_fx = new vl::Effect; ring_fx->setLOD( 0, fill_sh.get(), wire_sh.get() ); // LOD 0: pass #1 = fill_sh + pass #2 = wire_sh ring_fx->setLOD( 1, fill_sh.get() ); // LOD 1: pass #1 = fill_sh ring_fx->setLOD( 2, wire_sh.get() ); // LOD 2: pass #1 = wire_sh /* install the LOD evaluator to be used with the ring objects */ ring_fx->setLODEvaluator(lod_eval.get()); /* ring element lod #0 */ vl::ref<vl::Geometry> geom_0 = vl::makeIcosphere(vl::vec3(0,0,0),10,1); geom_0->computeNormals(); /* ring element lod #1 */ vl::ref<vl::Geometry> geom_1 = vl::makeBox(vl::vec3(0,0,0),6,6,6); geom_1->computeNormals(); /* ring element lod #2 */ vl::ref<vl::Geometry> geom_2 = vl::makePyramid(vl::vec3(0,0,0),6,6); geom_2->computeNormals(); /* generate the ring of objects */ for(int i=0;i<ring_obj_count; i++) { /* define actor position and add it to the scene */ vl::ref<vl::Transform> tr = new vl::Transform; vl::real t = 360.0f / ring_obj_count * i; vl::vec3 v = vl::mat4::getRotation(t,0,1,0) * vl::vec3(35,0,0); tr->setLocalMatrix( vl::mat4::getTranslation(v) ); rendering()->as<vl::Rendering>()->transform()->addChild(tr.get()); vl::ref<vl::Actor> act = sceneManager()->tree()->addActor( NULL, ring_fx.get(), tr.get() ); /* define which geometry to use for each LOD */ act->setLod(0, geom_0.get()); act->setLod(1, geom_1.get()); act->setLod(2, geom_2.get()); /* install the LOD evaluator*/ act->setLODEvaluator(lod_eval.get()); } } void updateScene() { /* animate the camera to rotate around the scene and bounce near/far */ float s = sin( vl::Time::currentTime() * vl::fPi * 2.0f / 10.0f ); vl::real t = pow((s+1.0f)/2.0f,2); vl::real x = t * 200 + 5; vl::vec3 eye( x, 0, 0 ); eye = vl::mat4::getRotation( vl::Time::currentTime() * 30.0f, 0, 1, 0 ) * eye; eye += vl::vec3(0,10+70*t,0); vl::mat4 m; m = vl::mat4::getLookAt( eye, vl::vec3(0,0,0), vl::vec3(0,1,0) ); rendering()->as<vl::Rendering>()->camera()->setViewMatrix(m); } }; // Have fun!