Is there any article about this or do OpenGL support this render to
texture feature maybe?
On Tue, 27 Nov 2007 14:05:02 +0100, Robert Osfield
<[EMAIL PROTECTED]> wrote:
> Hi Johan,
>
> Doing a per vertex operation on the CPU that requires a round trip to
> the graphics hardware is doomed to being very very slow indeed.
>
> If you have complex lighting calculations then try a technique like
> deferred lighting/shading - render the scene to a depth texture then
> in a second pass use this depth texture to compute normals and
> required lighting. The advantage of this approach is that you one
> compute the lighting for the pixels actually on screen, rather than
> for every fragment.
>
> Robert.
>
> On Nov 27, 2007 12:54 PM, Johan Johnsson <[EMAIL PROTECTED]> wrote:
>> I use below code to see if the vertex is occluded or not by objects
>> infront of it. This is apart of the lighting check to see if the
>> lightalgoritm needs to be runned on the pixel.
>>
>>
>> case GLREADPIXELS:
>> {
>> osg::Vec3 win; // Space For Returned
>> Projected
>> Coords
>> GLfloat bufferZ = 0.0f;// Here We Will Store The
>> Read
>> Z From The Buffer
>>
>>
>> osgViewer::Viewer::Cameras cameras;
>> m_viewer->getCameras(cameras);
>>
>> osg::ref_ptr<osgUtil::SceneView> sv = new
>> osgUtil::SceneView();
>>
>> for(osgViewer::Viewer::Cameras::iterator it =
>> cameras.begin(); it != cameras.end(); ++it)
>> {
>> sv->setCamera(*it);
>> sv->projectObjectIntoWindow(absolutePos, win);
>>
>> glReadPixels(win.x(), win.y(), 1, 1,
>> GL_DEPTH_COMPONENT, GL_UNSIGNED_INT_8_8_8_8_REV, &bufferZ);
>> //std::cout << bufferZ << "\t" << win.x() << "\t"
>> <<
>> win.y() << "\t" << win.z() << std::endl;
>>
>> if(bufferZ < win.z())
>> {
>> return true;
>> }
>> else
>> {
>> return false;
>> }
>> }
>> }
>> break;
>>
>> }
>>
>>
>>
>>
>>
>>
>> On Tue, 27 Nov 2007 13:48:47 +0100, Robert Osfield
>> <[EMAIL PROTECTED]> wrote:
>>
>> > Hi Johan,
>> >
>> > It would be worth stepping back a bit and explaining from a high level
>> > what you are trying to do in terms of doing occlusion testing, as
>> > there are many ways to do occlusion testing, one can't really answer
>> > what would be the best technique without knowing more about the
>> > problem you are wanting to solve.
>> >
>> > On Nov 27, 2007 12:27 PM, Johan Johnsson <[EMAIL PROTECTED]> wrote:
>> >> Hi !
>> >>
>> >> i wonder over something in my occluding technique: does openGL have
>> >> anything that is faster than
>> >> glReadPixels(win.x(), win.y(), 1, 1, GL_DEPTH_COMPONENT,
>> >> GL_UNSIGNED_INT_8_8_8_8_REV, &bufferZ); to get the depth from each
>> >> pixel?,
>> >> if not what i suggested to do ? Ive been thinking of making a shader
>> out
>> >> of it , but im not sure yet.
>> >>
>> >> --
>> >> Mr. Johan Johnsson
>> >> AutoSim AS, Strandveien 106, 9006 Tromsø
>> >> Visit us at http://www.autosim.no
>> >> _______________________________________________
>> >> osg-users mailing list
>> >> [email protected]
>> >>
>> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
>> >>
>> > _______________________________________________
>> > osg-users mailing list
>> > [email protected]
>> >
>> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
>>
>>
>>
>> --
>>
>> Mr. Johan Johnsson
>> AutoSim AS, Strandveien 106, 9006 Tromsø
>> Visit us at http://www.autosim.no
>> _______________________________________________
>> osg-users mailing list
>> [email protected]
>> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
>>
> _______________________________________________
> osg-users mailing list
> [email protected]
> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
--
Mr. Johan Johnsson
AutoSim AS, Strandveien 106, 9006 Tromsø
Visit us at http://www.autosim.no
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