Matrix multiplication without effect

OpenGL
1

Hello,

I am doing a texture coordinate calculation in my vertex shader for a projective lighting. Therefore I need to multiply the gl_ModelViewMatrix with my lightViewingMatrix, but no matter which values this matrix contains, it doesn’t change my results.
I hope anybody can help me…

here is what i’m doing:

  
"varying vec4 projPos;"//projected light-texture coord
"void main(void)"
"{"
// light projection matrix
"   mat4 lightProjMat= (0.68,0.0,0.0,0.0,    "
"                       0.0,2.85,0.0,0.0,    "
"                       0.0,0.0,-0.04,0.0,   "
"                       0.0,0.0,-1.04,1.0);  "
   //light ViewTransformation Matrix:
"   mat4 lightViewMat= (1.0,0.0,0.0,0.0,     "//column 1: x-axis light-CS
"                       0.0,1.0,0.0,0.0,     "//column 2: y-axis light-CS
"                       0.0,0.0,1.0,0.0,     "//column 3: z-axis light-CS
"                       8.35,-1.48,-0.5,1.0);"//column 4: translation light
// Scale and translate
"   mat4 scaleTranslMat= (0.5,0.0,0.0,0.0,   "
"                         0.0,0.5,0.0,0.0,   "
"                         0.0,0.0,0.5,0.0,   "
"                         0.5,0.5,0.5,1.0);  "
"  projPos = scaleTranslMat * lightProjMat * lightViewMat * gl_ModelViewMatrix * gl_Vertex;"
"  gl_TexCoord[0]  = gl_MultiTexCoord0;"
"  gl_Position = ftransform();"
"}"

the problem is, that none of my matrices takes effect :frowning:

Can anyone tell me what’s wrong here? I think it’s a general problem, because as I mentioned it doesn’t matter what the matrices contain…

thanks
Simon

2

i believe u need to do mat4 fdf = mat4(…)
ie use a constructor, though this error should show up in the compiler

3

What does your fragment shader look like?

4

indeed, the mat(…) has really been the problem, thank you zed…
(my fragment shader only does a texture lookup with the coordinate projPos)

5

Wouldn’t it be better to put something like in the global context and declare it as const mat4 … or it doesn’t matter?

6

yes, I think that would be better, but I only coded this as a test…

7

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