The transform below for the orthogonal projection is indeed linear, mapping [n,f] to [-1,1] in linear fashion.
If you want to linearize depth with a perspective projection (i.e. survive the perspective divide between the vertex and fragment shader), here's a way to do that. The example uses HLSL but it gets the point across... http://www.mvps.org/directx/articles/linear_z/linearz.htm Another interesting discussion related to linear depth using W-buffers can be found at http://www.mvps.org/directx/articles/using_w-buffers.htm Just make sure you have support for W buffers... -Shayne -----Original Message----- From: osg-users-boun...@lists.openscenegraph.org [mailto:osg-users-boun...@lists.openscenegraph.org] On Behalf Of "Martin Großer" Sent: Wednesday, August 24, 2011 5:58 AM To: OpenSceneGraph Users Subject: Re: [osg-users] Is the Z-Buffer linear or non-linear? Hello, I think I got it. Correct me if I am wrong, if I use an orthogonal projection I get linear Z-Buffer values. If I use a perspective projection I get non-linear values. The Z-Buffer value (z') of a perspective projection is: z' = (far + near) / (far - near) + 1/z ((-2 * far * near)/(far-near)) The Z-Buffer value (z') of a orthogonal projection is: z' = 2 * ((z-near)/(far-near))-1 So, I use a orthogonal projection therefore I get a linear Z-Buffer. I hope that is right. Cheers Martin -------- Original-Nachricht -------- > Datum: Wed, 24 Aug 2011 10:01:23 +0200 > Von: "Martin Großer" <grosser.mar...@gmx.de> > An: osg-users@lists.openscenegraph.org > Betreff: [osg-users] Is the Z-Buffer linear or non-linear? > Hello, > > I am completely confused about the Z-Buffer. I thought it is non-linear > but now I read a lot in forums and now I am not sure about that. The reason > about this question is I want render linear depth values into a texture. I > think, I can do it with this shader: > > varying float depth; > uniform float near; > uniform float far; > void main(void) > { > vec4 viewPos = gl_ModelViewMatrix * gl_Vertex; > depth = (-viewPos.z-near)/(far-near); > gl_Position = ftransform(); > }; > > > varying float depth; > void main(void) > { > gl_FragDepth = depth; > } > > But the poor think is all other shader will be overwritten. > > Now I use this: > > _rendertarget->setInternalFormat(GL_DEPTH_COMPONENT); > _cam->setClearMask(GL_DEPTH_BUFFER_BIT); > _cam->setRenderTargetImplementation(osg::Camera::FRAME_BUFFER_OBJECT); > _cam->attach(osg::Camera::DEPTH_BUFFER, _rendertarget); > _cam->setRenderOrder(::osg::Camera::PRE_RENDER, 0); > > But this is nonlinear, isn't it? > > I hope someone can help me about this. > > Thanke you very much. > > Martin > -- > NEU: FreePhone - 0ct/min Handyspartarif mit Geld-zurück-Garantie! > Jetzt informieren: http://www.gmx.net/de/go/freephone > _______________________________________________ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org -- Empfehlen Sie GMX DSL Ihren Freunden und Bekannten und wir belohnen Sie mit bis zu 50,- Euro! https://freundschaftswerbung.gmx.de _______________________________________________ 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
