[osg-users] how to get an unclamped float color buffer?

Ralph Kern usenet04 at rk-se.de
Thu Oct 25 07:19:39 PDT 2007


hi folks,

I'm looking for some way to get unclamped floating point values out of a
render buffer. My goal is to produce HDRI images.

I can fetch the image as rgb byte pixels, but I'm wondering how to get
float values which may be greater than 1.0.

I'm working on a ATI Radeon X1600.

My current framework is like that:

> int width = 512;
> int height = 512;
> osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;
> traits->x = 0;
> traits->y = 0;
> traits->width = width;
> traits->height = height;
> traits->windowDecoration = false;
> traits->doubleBuffer = false;
> traits->sharedContext = 0;
> traits->pbuffer = true;
> 
> osg::ref_ptr<osg::GraphicsContext> gc = osg::GraphicsContext::createGraphicsContext(traits.get());
> 
> if (!gc.valid())
> {
> 	osg::notify(osg::NOTICE)<<"Failed to create pbuffer, failing back to normal graphics window."<<std::endl;
> 
> 	traits->pbuffer = false;
> 	gc = osg::GraphicsContext::createGraphicsContext(traits.get());
> }
> 
> if (gc.valid()) 
> {
> 	gc->realize();
> 	gc->makeCurrent();
> 	osg::ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer;
> 	viewer->getCamera()->setGraphicsContext(gc.get());
> 	viewer->getCamera()->setViewport(0,0,width,height);
> 	viewer->setThreadingModel(osgViewer::Viewer::SingleThreaded);
> 
> 	// Init the main Root Node/Group
> 	osg::ref_ptr<osg::Group> _root = new osg::Group;
> 	osg::Shape *shape = new osg::Cylinder(Vec3f(0.5,0.5,-0.5), .4, .2);
> 	osg::ShapeDrawable *drawable = new osg::ShapeDrawable(shape);
> 	drawable->setColor(Vec4(1,1,0,1));
> 	osg::Geode *geode = new osg::Geode();
> 	geode->addDrawable(drawable);
> 
> 	_root->addChild(geode);
> 	_root->getOrCreateStateSet()->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
> 
> 	viewer->setSceneData(_root.get());
> 
> 	image = new osg::Image;
> 	image->allocateImage(width, height, 1, GL_RGB, GL_UNSIGNED_BYTE);
> 	viewer->getCamera()->attach(osg::Camera::COLOR_BUFFER, image.get());
> 	viewer->getCamera()->setRenderTargetImplementation(osg::Camera::FRAME_BUFFER_OBJECT);
> 	viewer->getCamera()->setClearColor(Vec4(.7,0,0,0));
> 	viewer->getCamera()->setProjectionMatrixAsOrtho(0, 1, 0, 1, 0, 1);
> 	viewer->getCamera()->setViewMatrix(matrix);
> 
> 	viewer->frame();
> 	viewer->getCamera()->detach(osg::Camera::COLOR_BUFFER);
> 
> 	osgDB::writeImageFile(*image,std::string("C:\\tmp\\buffer.tif", NULL);
> }


regards Ralph Kern




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