Enabling face culling will improve performance only when rendering is
fill-limited. If you're vertex-limited, face culling will not affect performance.
-Paul
On 5/29/2012 2:48 PM, Gio wrote:
Hello,
I am developing an application for iphone and ipod touch using openscenegraph.
It is an augmented reality application and I have to load a very complex model.
The original 3d model has 5 million vertices.
Since I am using a mobile platform which is limited in computational power I
simplified the model using 3d studio max. I reduced the size of the model from
500Mb to 4.2 Mb using proOptimizer.
The model now has in total about 36,000 vertices and about 53,000 faces.
I am able to render it but frame rate is slow. I'd like to improve performance
using back face culling. The point is I don't know how to activate it (if it is
possible):
I tried with these lines of code but frame rate is still low:
[code]
osg::StateSet* ss = _root->getOrCreateStateSet();
osg::CullFace* cf = new osg::CullFace(osg::CullFace::BACK );
ss->setAttribute( cf );
[/code]
I am using OpenGL ES 2.0 and shaders.
I setup the camera in this way:
[code]
//set the clear color of the camera to be transparent
_viewer->getCamera()->setClearColor(osg::Vec4(0.0f, 0.0f, 0.0f, 0.0f));
//set the clear mask for the camera
_viewer->getCamera()->setClearMask(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
_viewer->getCamera()->setRenderOrder(osg::CameraNode::PRE_RENDER);
_viewer->getCamera()->setComputeNearFarMode(osgUtil::CullVisitor::DO_NOT_COMPUTE_NEAR_FAR);
[/code]
I use DO_NOT_COMPUTE_NEAR_FAR because I need to set manually projection and
viewMatrix at every drawing cycle.
I also initially set viewport like this:
[code]
_viewer->getCamera()->setViewport(new osg::Viewport(0, 0,
graphicsContext->getTraits()->width, graphicsContext->getTraits()->height));
[/code]
The hierarchy of my object is structured as:
_root is a osg::MatrixTransform
my 3d model is divided in subparts.
all the subparts of my 3d model are direct child of _root and are of type
osg::Node
I hope you can give me some tips to improve performance. If you need some other
information about my setup I will be glad to give it.
Thank you.
Greetings,
John Moore
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