If I use #version 150 compatibility, do I still have to explicitly do the in out specifications, such as declaring out gl_FragColor in the frag shader?
SMesserschmidt wrote: > Hi Ethan, > > > Hello Sebastian, > > I read up on the differences between glsl 1.2 and 1.5 and then scimmed > > through the official GLSL 1.5 specification document. I then grepped the > > osg src and examples directories to see if I could find any #version 150 > > shaders (I could not). Are there any reference/example implementations of > > GLSL 1.5 shaders with OSG? I ask because it looks like GLSL 1.5 requires > > you to be more explicit with declaring inputs and outputs, including > > needing to pass things like the modelviewmatrix etc into the vertex shader > > as uniforms. Is this easily done? Examples? Do I have this assumption > > wrong? Thanks again, I promise I'm working hard on my end and not just > > fishing for easy answers > > > Simply go with the #version 150 compatible > It allows to use the built-in uniforms and varyings. So > gl_ModelViewMatrix and gl_Vertex etc. are still valid tokens. > This is less painful than doing the hard-core way. If you want to really > really go this way you have to setup vertex attribute aliasing in OSG, > but then you will really have to do a lot of things using visitors and > so on. So for starting, simply go with the compatibility profile and use > in/out only on your varyings. > > cheers > Sebastian > > > > > SMesserschmidt wrote: > > > > > Hi Ethan, > > > > > > > > > > Thanks again, it looks like I need to get up to speed with using "in" > > > > and "out" vs attribute and varying since I cut my teeth on older > > > > tutorials and apparently attribute and varying are officially > > > > deprecated and are supported through compatibility mode. I'm not used > > > > to needing historical context and having so many deprecated variables > > > > and different extensions to worry about like with GLSL. GLSL-land is a > > > > bit of a wild place to be! > > > > > > > > > > > Don't worry. You can also use varying safely. Just remember to use > > > something like #version 150 compatibility at the beginning of your > > > shaders. > > > However, it is better to get used to the new in, out as they are making > > > it much clearer what is input and what goes out your shader stage. > > > cheers > > > Sebastian > > > > > > > > > > -Ethan > > > > > > > > > > > > SMesserschmidt wrote: > > > > > > > > > > > > > Hi Ethan > > > > > > > > > > > > > > > > > > > > > Thanks Sebastian, > > > > > > > > > > > > I have in fact looked through every geometry shader tutorial I > > > > > > could find and have tried to implement a simple pass-through sahder > > > > > > identical to the one you posted, but when I add the geometry shader > > > > > > I just get a black screen with no OpenGL error messages, and if I > > > > > > remove the geometry shader and keep the vertex and frag shaders I > > > > > > get my normal scene. I'm not sure if maybe I'm missing passing > > > > > > through texture coordinates or something of that nature...? > > > > > > > > > > > > > > > > > > > > > > > Ok, you of course have to pass all your varyings through the geometry > > > > > shader. Thats the burden for using a geometry shader: you will have to > > > > > replicate the default funtionality. > > > > > For example: > > > > > Vertex shader: > > > > > > > > > > out vec4 v_color; > > > > > v_color =gl_Color; > > > > > > > > > > in geometry shader: > > > > > in vec4 v_color[]; > > > > > out vec4 g_color; > > > > > > > > > > g_color = color[i]; //i = vertex number > > > > > > > > > > and then finally in your fragment shader you can access: > > > > > > > > > > in g_color > > > > > > > > > > cheer > > > > > Sebastian > > > > > > > > > > > > > > > > > > > > > -Ethan > > > > > > > > > > > > > > > > > > SMesserschmidt wrote: > > > > > > > > > > > > > > > > > > > > > > > > > Hi Ethan, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, that makes sense that it would just be rendering a quad > > > > > > > > and that the original scene geometry would be lost. However, > > > > > > > > the GLSL geometry shader only accepts primitives of the type > > > > > > > > point, line, or triangle->is it perhaps rendering two triangles > > > > > > > > to the geometry shader to make up the quad? How would I even > > > > > > > > go about determining since there's no debugging available? > > > > > > > > > > > > > > > > But back to what I'm trying to do, I'm trying to use a geometry > > > > > > > > shader to calculate the min, max, mean, std dev, and histogram > > > > > > > > of an RTT texture. Fellow osg forum member Aurelius has > > > > > > > > advised me that he has working code that does this using > > > > > > > > geometry shaders and pointed me to: > > > > > > > > http://http.developer.nvidia.com/GPUGems3/gpugems3_ch41.html > > > > > > > > and > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > This seems rather complicated for a starter. Also it requires > > > > > > > feedback > > > > > > > buffers which I never got working in OSG, so there might be some > > > > > > > more > > > > > > > obstacles here. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > http://developer.amd.com/wordpress/media/2012/10/GPUHistogramGeneration_I3D07.pdf > > > > > > > > but the first example only has Cg code and not GLSL, and the > > > > > > > > second example is a paper that describers an algorithm but > > > > > > > > doesn't have any src. These are both potentially great > > > > > > > > resources, but I'm struggling to just get a basic pass-through > > > > > > > > geometry shader working to get some sort of starting point. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Geometry shaders are really simple. You simply need to know your > > > > > > > input > > > > > > > primitives. > > > > > > > A very basic geometry shader looks like this: > > > > > > > > > > > > > > > > > > > > > #version 400 > > > > > > > layout(triangles) in; //we receive triangles > > > > > > > layout(triangle_strip, max_vertices = 3) out; > > > > > > > > > > > > > > void main() > > > > > > > { > > > > > > > for (int i = 0; i < 3; ++i) > > > > > > > { > > > > > > > > > > > > > > vertex = gl_in[i].gl_Position; > > > > > > > gl_Position = vertex; > > > > > > > EmitVertex(); > > > > > > > } > > > > > > > > > > > > > > EndPrimitive(); > > > > > > > } > > > > > > > > > > > > > > But seriously, there are examples in OSG touching geometry > > > > > > > shaders and > > > > > > > there are plenty of tutorials about glsl and shaders. > > > > > > > > > > > > > > cheers > > > > > > > Sebastian > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > As a side note, I am also considering using a compute shader > > > > > > > > since this would be the more natual fit for this type of > > > > > > > > algorithm while the geometry shader method is more of a "hack" > > > > > > > > that goes against the original intention of the geometry > > > > > > > > shader, but I'd be happy using either method, I'm just trying > > > > > > > > to get some traction on either of them. > > > > > > > > > > > > > > > > -Ethan > > > > > > > > > > > > > > > > > > > > > > > > SMesserschmidt wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Am 18.11.2013 15:32, schrieb Ethan Fahy: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Hello, > > > > > > > > > > > > > > > > > > > > Preface: I realize this question comes about because I've > > > > > > > > > > never really learned OpenGL/GLSL from the ground up and am > > > > > > > > > > likely missing some simple concepts, but I mostly have been > > > > > > > > > > coasting by at the osg middleware level and have been doing > > > > > > > > > > OK so far. > > > > > > > > > > > > > > > > > > > > If I want to do some simple post-processing I can create a > > > > > > > > > > render-to-texture camera and render to the framebuffer. I > > > > > > > > > > can attach a texture to the framebuffer and then create > > > > > > > > > > another "screen" camera to render that texture to the > > > > > > > > > > screen. I can add a GLSL shader program to this texture so > > > > > > > > > > that before the texture gets rendered to the screen it gets > > > > > > > > > > an effect added to it using the shaders. > > > > > > > > > > > > > > > > > > > > When I use shaders attached to 3-D model nodes in the scene > > > > > > > > > > itself, the meaning of the vertex and frag shaders is easy > > > > > > > > > > to understand->the vertices of the 3-D model are the > > > > > > > > > > vertices referenced in the vertex shader. However, When I > > > > > > > > > > render my scene to a texture and then do a simple > > > > > > > > > > pass-through vertex and frag shader combo, what is the > > > > > > > > > > meaning of the vertices in this scenario? I had assumed > > > > > > > > > > that once you render your scene to a texture, all knowledge > > > > > > > > > > of the original scene's geometry and vertex locations has > > > > > > > > > > been lost, is this true? If so, then what vertices am I > > > > > > > > > > dealing with? It's easy enough to follow along with > > > > > > > > > > examples and to use a simple pass-through vertex shader, > > > > > > > > > > but I'd like to understand this better because I now want > > > > > > > > > > to insert a geometry shader in between the vertex and frag > > > > > > > > > > shaders and again I'm not sure whether to use point, line, > > > > > > > > > > or triangle in my geometry shader as the primitive type > > > > > > > > > > because I thought that the geometry and primitives of the or igin > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > al s > > > > > > > > > cene > > > > > > > > > > > > > > > > > > > wou > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ld > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > b > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > e lost after rendering to texture. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Usually when doing the post-processing pass you will be > > > > > > > > > rendering to a > > > > > > > > > fullscreen quad. So the vertices you are dealing with are > > > > > > > > > those of the > > > > > > > > > quad you are rendering too. > > > > > > > > > And yes, If you don't any further actions, rendering to > > > > > > > > > texture will not > > > > > > > > > preserve the information on your orignal vertices etc. > > > > > > > > > The question is what you want to achieve. A geometry shader > > > > > > > > > inbetween > > > > > > > > > your postprocessing pass will work on the quads vertices. > > > > > > > > > Maybe you should elaborate which kind of post processing you > > > > > > > > > want to > > > > > > > > > achieve, so we can help you here. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > What am I missing here? Any clarification is most welcome. > > > > > > > > > > > > > > > > > > > > -Ethan > > > > > > > > > > > > > > > > > > > > ------------------ > > > > > > > > > > Read this topic online here: > > > > > > > > > > http://forum.openscenegraph.org/viewtopic.php?p=57281#57281 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > > > > > > > osg-users mailing list > > > > > > > > > > > > > > > > > > > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > > > > > > osg-users mailing list > > > > > > > > > > > > > > > > > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > > > > > > > > > > > > > > > > ------------------ > > > > > > > > > Post generated by Mail2Forum > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ------------------ > > > > > > > > Read this topic online here: > > > > > > > > http://forum.openscenegraph.org/viewtopic.php?p=57285#57285 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > > > > > osg-users mailing list > > > > > > > > > > > > > > > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > > > > osg-users mailing list > > > > > > > > > > > > > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > > > > > > > > > > > > ------------------ > > > > > > > Post generated by Mail2Forum > > > > > > > > > > > > > > > > > > > > > > > > > > > ------------------ > > > > > > Read this topic online here: > > > > > > http://forum.openscenegraph.org/viewtopic.php?p=57298#57298 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > > > osg-users mailing list > > > > > > > > > > > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > > osg-users mailing list > > > > > > > > > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > > > > > > > > ------------------ > > > > > Post generated by Mail2Forum > > > > > > > > > > > > > > ------------------ > > > > Read this topic online here: > > > > http://forum.openscenegraph.org/viewtopic.php?p=57303#57303 > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > > osg-users mailing list > > > > > > > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > > > > > > > > > > > > _______________________________________________ > > > osg-users mailing list > > > > > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > > > > ------------------ > > > Post generated by Mail2Forum > > > > > :) > > > > ------------------ > > Read this topic online here: > > http://forum.openscenegraph.org/viewtopic.php?p=57323#57323 > > > > > > > > > > > > _______________________________________________ > > osg-users mailing list > > > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > > > > _______________________________________________ > osg-users mailing list > > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > ------------------ > Post generated by Mail2Forum ------------------ Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=57325#57325 _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
