Hello Robert, that is correct with the frame rate. 380 fps is ok, but it is a very simple scene. But what happens if I have 150.000 polygons? My apprehension is that the frame rate will break down. You wrote there are an approach to render to texture only on the gpu. How can I do that? With a GLSL-Shader?
I want to give you a little introduction about my motivation. The reason is I want to move the pixels on my screen. For example I want to move the color information from [0,0] to [3,3] and so on. I guess it can be solve on the gpu. Cheers, Martin -------- Original-Nachricht -------- > Datum: Fri, 26 Nov 2010 13:52:44 +0000 > Von: Robert Osfield <robert.osfi...@gmail.com> > An: OpenSceneGraph Users <osg-users@lists.openscenegraph.org> > Betreff: Re: [osg-users] My Render to Texture is very slow > Hi Martin, > > There isn't a technical problem, just a need of greater understanding > of what's happening in OpenGL and the CPU and GPU. OpenGL has a deep > FIFO buffer than your application put all the required OpenGL tokens > and data into, the OpenGL driver packages this up and send it the GPU. > This pipeline enables the CPU and GPU to be run asynchronously, and > at perform at a high performance level. > > However, the asynchronous nature provided by the OpenGL FIFO is broken > any time you need to get data from GPU, a glReadPixels is one such > operation - to handle this OpenGL call the driver has to block the > application thread and wait for all the data in the FIFO to be > processed by the GPU, then it can copy the data back to the CPU and > return it to your application. This round trip to the GPU is > therefore extremely costly. In your case attaching an osg::Image to a > RTT Camera forces the OSG to use a glReadPixels. > > There are different techniques to address this issue, which is > appropriate depends upon your needs. One approach is to do all render > to texture work down on the GPU and avoid ever needing to copy data > back to the main memory. Another approach is to use double buffer > PBO's to read the data back in the subsequent frame. > > However, in all these changes perhaps they aren't needed. You are > getting 380fps which is many times faster than screen refresh, and if > you app is rev'ing faster than screen refresh then you are wasting > your time worrying about optimizing. Just stick vsync on, reduce your > energy consumption and noise pollution, and enjoy the better visual > quality. If there does come a day when you app starts breaking frame > then worry about it. > > Robert. > > 2010/11/26 "Martin Großer" <grosser.mar...@gmx.de>: > > Hello, > > > > I've implemented a RTT example with osg and I my scene object is the > cessna.osg. Without the RTT-Implementation I have around 4500 fps. But with > the RTT I have only 380 fps. My Texture is 512 x 512. What is the Problem? > > > > I have got a GeForce 470 and a intel processor i7 820. I guess the > hardware is ok. My Implementation is: > > > > osg::Vec3 eye(40,-40,40); > > osg::Vec3 point(0,0,0); > > > > c->addChild(in); > > c->setReferenceFrame(osg::Transform::ABSOLUTE_RF); > > > > c->setProjectionMatrixAsPerspective(30.0,1.0,0.1,100.0); > > c->setViewMatrixAsLookAt(eye,point,osg::Vec3(0,0,1)); > > c->setClearColor(osg::Vec4(0.4,0.0,0.0,0.0)); > > c->setViewport(0,0,512,512); > > c->setClearMask( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ); > > c->setRenderOrder(osg::Camera::PRE_RENDER, 0); > > c->setRenderTargetImplementation( osg::Camera::FRAME_BUFFER_OBJECT ); > > c->attach(osg::Camera::COLOR_BUFFER, img, 0, 0); > > > > Is my implementation the problem? > > > > In OpenGL I can use glCopyTexImage2D(...). There are a Wrapper in OSG > for this functionality? > > > > Cheers, > > > > Martin > > -- > > Neu: GMX De-Mail - Einfach wie E-Mail, sicher wie ein Brief! > > Jetzt De-Mail-Adresse reservieren: http://portal.gmx.net/de/go/demail > > _______________________________________________ > > osg-users mailing list > > osg-users@lists.openscenegraph.org > > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org -- GMX DSL Doppel-Flat ab 19,99 €/mtl.! Jetzt auch mit gratis Notebook-Flat! http://portal.gmx.net/de/go/dsl _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
