OpenSceneGraph - 隱形Cloack

Question

我是新的使用OSG，我有一些問題試圖解決問題。

我創建了一個場景（一個四邊形和兩個球體，有一個固定的背景），我試圖用透明四邊形遮擋其中一個球體。我的意思是，製作一張「隱形衣」，所以我可以通過它看到背景圖像，但不能看到它背後的球體（或任何在投影線中的物體）。

我完全卡住了，因爲我一直在做的所有測試都沒有讓我接近我想要的東西。如果你能幫助我，我會非常感激，任何想法（或代碼！）都會比歡迎！ =）

我附上了我用來做測試的簡單場景的代碼。

#include <osg/Geometry> 
#include <osg/Geode> 
#include <osg/Depth> 
#include <osg/Texture2D> 
#include <osgDB/ReadFile> 
#include <osgViewer/Viewer> 
#include <osg/ShapeDrawable> 
#include <osg/BlendFunc> 
#include <osgGA/TrackBallManipulator> 

int main() 
{ 
osg::ref_ptr<osg::Texture2D> texture = new osg::Texture2D; 
osg::ref_ptr<osg::Image> image = osgDB::readImageFile("C:/OpenSceneGraph-3.4.0/esc.jpg"); 
texture->setDataVariance(osg::Object::DYNAMIC); 
texture->setResizeNonPowerOfTwoHint(false); 
texture->setImage(image.get()); 

// Background 
osg::ref_ptr<osg::Drawable> quad = osg::createTexturedQuadGeometry(osg::Vec3(),osg::Vec3(1.0f,0.0f,0.0f),osg::Vec3(0.0f, 1.0f, 0.0f)); 
quad->getOrCreateStateSet()->setTextureAttributeAndModes(0, texture.get()); 

osg::ref_ptr<osg::Geode> geodeBack = new osg::Geode; 
geodeBack->addDrawable(quad.get()); 

osg::ref_ptr<osg::Camera> camera = new osg::Camera; 
camera->setCullingActive(false); 
camera->setClearMask(0); 
camera->setAllowEventFocus(false); 
camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF); 
camera->setRenderOrder(osg::Camera::POST_RENDER); 
camera->setProjectionMatrix(osg::Matrix::ortho2D(0.0, 1.0, 0.0, 1.0)); 
camera->addChild(geodeBack.get()); 

osg::StateSet* ss = camera->getOrCreateStateSet(); 
ss->setMode(GL_LIGHTING, osg::StateAttribute::OFF); 
ss->setMode(GL_DEPTH, osg::StateAttribute::ON); 
ss->setAttributeAndModes(new osg::Depth(osg::Depth::LEQUAL,0.99,1.0)); 


// Quad geometry 
osg::ref_ptr<osg::Vec3Array> vertices = new osg::Vec3Array; 
vertices->push_back(osg::Vec3(-1.0f, 1.0f,-1.0f)); 
vertices->push_back(osg::Vec3(0.0f, 1.0f,-1.0f)); 
vertices->push_back(osg::Vec3(0.0f, 1.0f, 0.0f)); 
vertices->push_back(osg::Vec3(-1.0f, 1.0f, 0.0f)); 

osg::ref_ptr<osg::Vec3Array> normals = new osg::Vec3Array; 
normals->push_back(osg::Vec3(0.0f,-1.0f, 0.0f)); 

osg::ref_ptr<osg::Vec4Array> colors = new osg::Vec4Array; 
colors->push_back(osg::Vec4(1.0f, 1.0f, 1.0f, 0.0f)); 

osg::ref_ptr<osg::Geometry> quad2 = new osg::Geometry; 
quad2->setVertexArray(vertices.get()); 
quad2->setNormalArray(normals.get()); 
quad2->setNormalBinding(osg::Geometry::BIND_OVERALL); 
quad2->setColorArray(colors.get()); 
quad2->setColorBinding(osg::Geometry::BIND_OVERALL); 

quad2->addPrimitiveSet(new osg::DrawArrays(GL_QUADS, 0, 4)); 

osg::ref_ptr<osg::Geode> geodeTransp = new osg::Geode; 
geodeTransp->addDrawable(quad2.get()); 


osg::ref_ptr<osg::BlendFunc> blendFunc = new osg::BlendFunc; 
blendFunc->setFunction(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); 
osg::StateSet* stateset = geodeTransp->getOrCreateStateSet(); 
stateset->setAttributeAndModes(blendFunc); 

// I'd see both spheres if I uncomment this. Otherwise I'd see the blue osg default background 
//stateset->setRenderingHint(osg::StateSet::TRANSPARENT_BIN); 

// Sphere 1 
osg::ref_ptr<osg::ShapeDrawable> shape1 = new osg::ShapeDrawable; 
shape1->setShape(new osg::Sphere(osg::Vec3(-0.3f,0.5f,-0.3f), 0.2f)); 
shape1->setColor(osg::Vec4(0.0f, 0.0f, 1.0f, 1.0f)); 

// Sphere 2 
osg::ref_ptr<osg::ShapeDrawable> shape2 = new osg::ShapeDrawable; 
shape2->setShape(new osg::Sphere(osg::Vec3(-0.7f,1.5f,-0.7f), 0.2f)); 
shape2->setColor(osg::Vec4(0.0f, 1.0f, 0.0f, 1.0f)); 

osg::ref_ptr<osg::Geode> geodeFront = new osg::Geode; 
geodeFront->addDrawable(shape1.get()); 
geodeFront->addDrawable(shape2.get()); 

osg::ref_ptr<osg::Group> root = new osg::Group; 
root->addChild(camera.get()); 
root->addChild(geodeTransp.get()); 
root->addChild(geodeFront.get()); 

osgViewer::Viewer viewer; 
viewer.setSceneData(root.get()); 

viewer.setCameraManipulator(new osgGA::TrackballManipulator()); 
osg::Vec3d eye(-0.5, -3.0, -0.5); 
osg::Vec3d center(-0.5, 0.0, -0.5); 
osg::Vec3d up(0.0, 0.0, 1.0); 

viewer.getCamera()->setViewMatrixAsLookAt(eye, center, up); 

viewer.realize(); 
while(!viewer.done()) { 
    viewer.frame(); 
} 
return 0; 
} 

由於提前，

乾杯， 阿爾瓦羅

Answer 1

如果我理解正確的話你以後，你應該簡單地在這個特定的順序呈現：

• 背景飛機
• 「隱形」四格
• 所有其他物件（即兩個領域等等）

因此，所有呈現在四元組之後的東西，如果恰好在它後面，它將被掩蓋。在OSG中，您可以通過明確分配用於其狀態集中不同（羣組）的渲染器來實現該目的：

osg::StateSet* stateset = backgroundNode->getOrCreateStateSet(); 
stateset->setRenderBinDetails(1, "RenderBin"); 
// and increasing the number for the other nodes...