// reference frame and pre-render
osg::ref_ptr<osg::Camera> camera = new osg::Camera();
camera->setReferenceFrame(osg::Camera::ABSOLUTE_RF);
camera->setRenderOrder(osg::Camera::PRE_RENDER);
// Set the camera's projection matrix to reflect the
// world of the geometries that will appear in the texture
camera->setProjectionMatrixAsOrtho2D(minx, maxx, miny, maxy);
//Set the camera's viewport to the same size of the texture
camera->setViewport(0, 0, textureWidth, textureHeight);
// Set the camera's clear color and masks
camera->setClearColor(clearColor);
camera->setClearMask(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//Create the texture image
osg::ref_ptr<osg::Image> image = new osg::Image();
image->allocateImage(textureWidth,
textureHeight,
1, // 2D texture is 1 pixel deep
GL_RGBA,
GL_UNSIGNED_BYTE);
image->setInternalTextureFormat(GL_RGBA8);
// Create the texture object and set the image
osg::ref_ptr<osg::Texture2D> texture2D = new osg::Texture2D();
texture2D->setImage(image);
// Attach the texture to the camera. You can also attach
// the image to the camera instead. Attaching the image may
// work better in the Windows Remote Desktop
camera->attach(osg::Camera::COLOR_BUFFER, texture2D.get());
// Add the geometries that will appear in the texture to the camera
camera->addChild(geometriesInTexture);
// Create a geode to display the texture
osg::ref_ptr<osg::Geode> geode = new osg::Geode();
// Create a geometry for the geode
osg::ref_ptr<osg::Geometry> geometry = new osg::Geometry();
geode->addDrawable(geometry);
// The coordinates can be different if we want to display the
// texture at a location different from the coordinates of the
// geometries inside the texture
osg::ref_ptr<osg::Vec3Array> vertexArray = new osg::Vec3Array();
vertexArray->push_back(osg::Vec3(minx, miny, minz));
vertexArray->push_back(osg::Vec3(maxx, miny, minz));
vertexArray->push_back(osg::Vec3(maxx, maxy, minz));
vertexArray->push_back(osg::Vec3(minx, maxy, minz));
geometry->setVertexArray(vertexArray);
// The geometry color for the texture mapping should be white
// (1.f, 1.f, 1.f, 1.f) so that color blending won't affect
// the texture real color
osg::ref_ptr<osg::Vec4Array> colorArray = new osg::Vec4Array();
colorArray->push_back(osg::Vec4(1.f, 1.f, 1.f, 1.f));
geometry->setColorArray(colorArray);
geometry->setColorBinding(osg::Geometry::BIND_OVERALL);
// We are using the entire texture by using the four corners
// of the texture coordinates
osg::ref_ptr<osg::Vec2Array> texCoordArray = new osg::Vec2Array();
texCoordArray->push_back(osg::Vec2(0.f, 0.f));
texCoordArray->push_back(osg::Vec2(1.f, 0.f));
texCoordArray->push_back(osg::Vec2(1.f, 1.f));
texCoordArray->push_back(osg::Vec2(0.f, 1.f));
geometry->setTexCoordArray(0, texCoordArray);
// We always create a square texture.
geometry->addPrimitiveSet(
new osg::DrawArrays(GL_TRIANGLE_FAN, 0, 4));
// Add the texture to the geode
geode->getOrCreateStateSet()->setTextureAttributeAndModes(
0, texture2D, osg::StateAttribute::ON);
// Make sure that we are using color blending
// and the transparent bin, since the features may not
// cover the entire texture and the empty
// space should be transparent.
geode->getOrCreateStateSet()->setRenderingHint(
osg::StateSet::TRANSPARENT_BIN);
osg::ref_ptr<osg::BlendFunc> blendFunc = new osg::BlendFunc;
blendFunc->setFunction(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
geode->getOrCreateStateSet()->setAttributeAndModes(blendFunc);
// Add both the rtt camera and the geode to the scene graph
sceneGraph->addChild(camera);
sceneGraph->addChild(geode);
* NOTE: If we only want to render one frame on the texture, we can remove the camera from the scene graph after the frame is rendered. The geode will still display the static texture in the scene graph properly.
