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gdoglz

cg get vertex shader parameters

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hi there, I've got a question about getting parameter values from a vertex shader in nvidia CG (as i have just started programming in cg). I know it is possible to set parameter values in the vertex shader thru cgGLSetParameterPointer() or cgGLSetParameter4f() functions among others. However, I wonder if there is a procedure to get variable values from the cg program during execution time. I'm using a simple program with cgGetParameterValuefr() and the code snippet is the following (from NeHe tutorials) BOOL Initialize (GL_Window* window, Keys* keys) { ... //Im skipping the Error checking functions for sake of clarity cgContext = cgCreateContext(); cgVertexProfile = cgGLGetLatestProfile(CG_GL_VERTEX); cgGLSetOptimalOptions(cgVertexProfile); cgProgram = cgCreateProgramFromFile(cgContext, CG_SOURCE, "CG/Wave.cg", cgVertexProfile, "main", 0); cgGLLoadProgram(cgProgram); position = cgGetNamedParameter(cgProgram, "IN.position"); res = cgGetNamedParameter(cgProgram, "result"); modelViewMatrix = cgGetNamedParameter(cgProgram, "ModelViewProj"); } void Draw (void) { ... glLoadIdentity (); ... cgGLSetStateMatrixParameter(modelViewMatrix, CG_GL_MODELVIEW_PROJECTION_MATRIX, CG_GL_MATRIX_IDENTITY); int p = -1; float* fTest; if (cg_enable) { cgGLEnableClientState(position); cgGLSetParameter4f(position, 0.5f, 1.0f, 0.5f, 1.0f); cgGLEnableProfile(cgVertexProfile); cgGLBindProgram(cgProgram); p = cgGetParameterValuefr(res, 4, fTest); cgGLDisableClientState(position); } And the vertex program is: struct appdata { float4 position : POSITION; }; struct vfconn { float4 HPos : POSITION; }; vfconn main(appdata IN, uniform float4x4 ModelViewProj, inout float4 result) { vfconn OUT; //not using it for the moment,but just left it for future purposes result = mul(ModelViewProj, IN.position); OUT.HPos = mul(ModelViewProj, IN.position); return OUT; } The problem is that when I perform the calculation in the vertex program I cannot get the updated variable 'result' (I always get the initial position value fTest = {0.5f, 1.0f, 0.5f, 1.0f}). I wonder if there is a proper way to get a parameter value from the vertex program using a diferent cg function or if I am screwing the whole thing up. Thanks a lot in advance for any ideas, gdoglz [Edited by - gdoglz on June 13, 2008 6:11:53 AM]

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