Hi Alex, don't worry about the bad news: we're here to "solve" problems: no problems = no fun :) I think that it should be possible to pass tangent values using gl_TexCoord variable. I used OpenCollada exporter in 3dstudio max with "export tangent/binormal" option turned on. In the .dae file created the are these lines:
<input semantic="VERTEX" source="#geom-Plane01-vertices" offset="0"/> <input semantic="NORMAL" source="#geom-Plane01-normals" offset="1"/> <input semantic="TEXCOORD" source="#geom-Plane01-map1" offset="2" set="1"/> <input semantic="TEXTANGENT" source="#geom-Plane01-map1-textangents" offset= "3" set="1"/> <input semantic="TEXBINORMAL" source="#geom-Plane01-map1-texbinormals"offset= "3" set="1"/> Now I know that tangent and binormal per-vertex values are described in the mesh file. How to read that values in the GLSL shader? Here it is how collada handles multiple texture: http://www.gamedev.net/community/forums/topic.asp?topic_id=529630&whichpage=1� ..so I tried to modify the .dae file to pass tangents and binormal values as multiple texture coordinates adding these lines: <input semantic="TEXCOORD" source="#geom-Plane01-map1" offset="2" set="0"/> [...] <bind_vertex_input semantic="TEXCOORD" input_semantic="TEXTANGENT"input_set= "1" set="1"></bind_vertex_input> <bind_vertex_input semantic="TEXCOORD" input_semantic="TEXBINORMAL"input_set= "1" set="2"></bind_vertex_input> ..and then I tried to access texture UV coords using gl_TexCoord[0], tangents coords using gl_TexCoord[1], and binormal coords using gl_TexCoord[2] but it doesn't seem to work. :\ Am I wasting my time, or it could be one possible solution? I was wanted to do the same thing a while back. Unfortunately, the answer > was pretty much that it can t be done in QC. It could potentially be > achieved with a 3rd-party plugin like Kineme 3D, but the Kineme developers > seemed to think the way QC is setup internally makes it very difficult to > pass arbitrary vertex attributes to GLSL shaders. > Sorry to be the bearer of bad news... > > a|x > >Hi, > >I'm trying to implement cone-step mapping shader in QC, and I got this > >problem: the GLSL vertex shader needs to know the tangent of each vertex. > As > >far as I know, GLSL lets to access to the per-vertex normal value using > the > >built-in attribute gl_Normal, but the tangent of each vertex needs to be > >passed from the OpenGL application (calculated when the mesh is loaded for > >example), or stored in the mesh file. > >So, i guess the right way to do that is to use per-vertex attribute like > >this in vertex shader: > > > >[...] > >attribute vec3 tangent; //The tangent of the current vertex > >[...] > > > >...but how can this attribute be passed to the GLSL shader for each > vertex? > >I also need per-vertex binormal value, but I guess it would be ok to > >calculculate its value once I got per-vertex normal and tangent values in > >this way: > > > >binormal = normalize(cross(normal, tangent)); > > > >Thank you for any kind of help! >
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