Re: [osg-users] starting with stencil buffer to achieve ray tracing
Hi Andrey, The OSG's intersection routines test the bounding spheres on the nodes in the scene graph and will automatically stop traversing if the intersector doesn't intersect with the subgraph. This means there is nothing to gain from trying avoid doing tests as the intersection visitor will already do it for you. Robert. On 30 November 2011 17:53, Andrey Ibe xry...@gmail.com wrote: hello good people! i need a bit of advice ragarding some more advanced rendering techniques. advanced for me, anyway. i am trying to build a simple ray tracing application on top of the basic osgviewer program. to start off, i am trying to look at the loaded model and decide where to cast rays, e.g. i don't want to cast any rays where the model would be missed. i was thinking of using the stencil buffer and the first thing i need is to draw say white pixels where the model is and say black pixels where the model is not. then display this buffer as the frame buffer, you know what i mean. is this possible? i remember doing something similar with GLUT long, long time ago. //if i was able to do this kind of evaluation on the per-pixel basis, i think, i could add some more advanced features like the color of the first hit object (instead of white) and then maybe continue with some real ray tracing, as i mention in the following lines.// later on, according to where the model would be hit (the white pixels), i would cast rays using line intersectors. haven't thought about details here yet. it would be kind of any of you if you could give me some pointers, especially for the first part with the buffers that i am currently dealing with - is it even possible? is my concept good? - for my knowledge in this area has gotten very poor :( and i am also new to the osg. thank you very much in advance. Andrey -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=44140#44140 ___ 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
Re: [osg-users] starting with stencil buffer to achieve ray tracing
Thank you, Robert. I won't implement this then. i realized later that this might be just a minor optimization, if the Kd-Trees were working properly. Cheers, Andrey -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=44666#44666 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] starting with stencil buffer to achieve ray tracing
thank you filip! this might just be what i was looking for :)
but i'm getting OpenGL errors here ...
Code:
Warning: detected OpenGL error 'invalid operation' at end of SceneView::draw()
Warning: detected OpenGL error 'invalid operation' at start of State::apply()
the letter one keeps piling up as the app runs.
i wrote this code into the main function just before calling the optimizer and
viewer.run();
Code:
osg::ref_ptrosg::Group rootNode = new osg::Group;
{
osg::Stencil* stencil = new osg::Stencil;
stencil-setFunction(osg::Stencil::ALWAYS, 1, ~0u);
stencil-setOperation(osg::Stencil::ZERO, osg::Stencil::ZERO,
osg::Stencil::REPLACE);
osg::StateSet* ssb1 = new osg::StateSet();
ssb1-setMode(GL_CULL_FACE, osg::StateAttribute::OFF);
ssb1-setAttributeAndModes(stencil, osg::StateAttribute::ON);
rootNode-setStateSet(ssb1);
}
rootNode-addChild(loadedModel.get());
viewer.getCamera()-setPostDrawCallback(new PostDrawCallback());
and then the callback
Code:
class PostDrawCallback : public osg::Camera::DrawCallback {
virtual void operator () (osg::RenderInfo renderInfo) const {
osg::ref_ptrosg::Image img = new osg::Image;
osg::View *view = renderInfo.getView();
int width = view-getCamera()-getViewport()-width();
int height = view-getCamera()-getViewport()-height();
img-readPixels(0, 0, width, height, GL_STENCIL_INDEX,
GL_UNSIGNED_BYTE);
}
};
if i comment out the readpixels method, the errors do not apear.
what am i missing [Question]
[Arrow]
--
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=44186#44186
___
osg-users mailing list
osg-users@lists.openscenegraph.org
http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] starting with stencil buffer to achieve ray tracing
Hi, The most simple thing that could it be is this: did you set up stencil buffer by calling osg::DisplaySettings::instance()-setMinimumNumStencilBits(); or creating context with stencil buffer? Cheers, Filip -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=44188#44188 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] starting with stencil buffer to achieve ray tracing
filip, that line of code solved the problem! thank you so much! now i have to bend the code i have a bit for my purpose. -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=44189#44189 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] starting with stencil buffer to achieve ray tracing
Hi, Use osg::Stencil on root node and set 1 where you draw (stencil func GL_ALWAYS). Use post draw callback on your camera. In callback save content of stencil buffer in osg::Image with readPixels() ... format GL_STENCIL_INDEX Inspect image. Cheers, Filip -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=44162#44162 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
[osg-users] starting with stencil buffer to achieve ray tracing
hello good people! i need a bit of advice ragarding some more advanced rendering techniques. advanced for me, anyway. i am trying to build a simple ray tracing application on top of the basic osgviewer program. to start off, i am trying to look at the loaded model and decide where to cast rays, e.g. i don't want to cast any rays where the model would be missed. i was thinking of using the stencil buffer and the first thing i need is to draw say white pixels where the model is and say black pixels where the model is not. then display this buffer as the frame buffer, you know what i mean. is this possible? i remember doing something similar with GLUT long, long time ago. //if i was able to do this kind of evaluation on the per-pixel basis, i think, i could add some more advanced features like the color of the first hit object (instead of white) and then maybe continue with some real ray tracing, as i mention in the following lines.// later on, according to where the model would be hit (the white pixels), i would cast rays using line intersectors. haven't thought about details here yet. it would be kind of any of you if you could give me some pointers, especially for the first part with the buffers that i am currently dealing with - is it even possible? is my concept good? - for my knowledge in this area has gotten very poor :( and i am also new to the osg. thank you very much in advance. Andrey -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=44140#44140 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] starting with stencil buffer to achieve ray tracing
Hi Andrey, Just a thought, but wouldn't this only work for orthographic projections? I believe the traditional ray tracing approach to this problem is to use an octree. Kim. On 30 November 2011 17:53, Andrey Ibe xry...@gmail.com wrote: hello good people! i need a bit of advice ragarding some more advanced rendering techniques. advanced for me, anyway. i am trying to build a simple ray tracing application on top of the basic osgviewer program. to start off, i am trying to look at the loaded model and decide where to cast rays, e.g. i don't want to cast any rays where the model would be missed. i was thinking of using the stencil buffer and the first thing i need is to draw say white pixels where the model is and say black pixels where the model is not. then display this buffer as the frame buffer, you know what i mean. is this possible? i remember doing something similar with GLUT long, long time ago. //if i was able to do this kind of evaluation on the per-pixel basis, i think, i could add some more advanced features like the color of the first hit object (instead of white) and then maybe continue with some real ray tracing, as i mention in the following lines.// later on, according to where the model would be hit (the white pixels), i would cast rays using line intersectors. haven't thought about details here yet. it would be kind of any of you if you could give me some pointers, especially for the first part with the buffers that i am currently dealing with - is it even possible? is my concept good? - for my knowledge in this area has gotten very poor :( and i am also new to the osg. thank you very much in advance. Andrey -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=44140#44140 ___ 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
Re: [osg-users] starting with stencil buffer to achieve ray tracing
basically, what i want to do is to cast primary rays from the camera (for each pixel on the screen) into the scene using line intersectors. then i want to retrieve normal of the intersection to be able to compute the direction of the secondary ray and then to cast it the way i cast the primary rays. i want to continue recursively until a certain point. with the buffer i want to optimize the number of the primary rays casted. ultimately, my goal is to render the scene normally using opengl pipeline into FBO, then turn on ray tracing for certain objects/materials in the scene. i need to know whether this is possible and in what ways can osg help. what i see as the greatest advantage are the intersetors and the osg's ability to compute the intersections automatically. i don't get the connection between the octree, which if i am not mistaken is a way of organizing the data or the scene, and my goal. neither i get the reason why this buffer thing would not work on perspective projection, if that's what you meant. thanks -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=44147#44147 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
