converting GLSL #130 segment to #330

Question

I have the following piece of shader code that works perfectly with GLSL #130, but I would like to convert it to code that works with version #330 (as somehow the #130 version doesn't work on my Ubuntu machine with a Geforce 210; the shader does nothing). After several failed attempts (I keep getting undescribed link errors) I've decided to ask for some help. The code below dynamically changes the contrast and brightness of a texture using the uniform variables Brightness and Contrast. I have implemented it in Python using PyOpenGL:

def createShader():
     """
     Compile a shader that adjusts contrast and brightness of active texture
     Returns
         OpenGL.shader - reference to shader
         dict - reference to variables that can be passed to the shader
     """

     fragmentShader = shaders.compileShader("""#version 130
     uniform sampler2D Texture;
     uniform float Brightness;
     uniform float Contrast;
     uniform vec4 AverageLuminance;

     void main(void)
     {
         vec4 texColour = texture2D(Texture, gl_TexCoord[0].st);
         gl_FragColor = mix(texColour * Brightness, 
                        mix(AverageLuminance, texColour, Contrast), 0.5);
     }
     """, GL_FRAGMENT_SHADER)
     shader = shaders.compileProgram(fragmentShader)

     uniform_locations = {
          'Brightness': glGetUniformLocation( shader, 'Brightness' ),
          'Contrast': glGetUniformLocation( shader, 'Contrast' ),
          'AverageLuminance': glGetUniformLocation( shader, 'AverageLuminance' ),
          'Texture': glGetUniformLocation( shader, 'Texture' )
     }
     return shader, uniform_locations

I've looked up the changes that need to made for the new GLSL version and tried changing the fragment shader code to the following, but then only get non-descriptive Link errors:

fragmentShader = shaders.compileShader("""#version 330
uniform sampler2D Texture;
uniform float Brightness;
uniform float Contrast;
uniform vec4 AverageLuminance;
in vec2 TexCoord;
out vec4 FragColor;

void main(void)
{
    vec4 texColour = texture2D(Texture, TexCoord);
    FragColor = mix(texColour * Brightness, 
                mix(AverageLuminance, texColour, Contrast), 0.5);
}
""", GL_FRAGMENT_SHADER)

Is there anyone that can help me with this conversion?

Answer 1

I doubt that raising the shader version profile will solve any issue. #version 330 is OpenGL-3.3 and according to the NVidia product website the maximum OpenGL version supported by the GeForce 210 is OpenGL-3.1, i.e. #version 140

I created no vertex shader cause I didn't think I'd need one (I wouldn't know what I should make it do). It worked before without any vertex shader as well.

Probably only as long as you didn't use a fragment shader or before you were attempting to use a texture. The fragment shader needs input variables, coming from a vertex shader, to have something it can use as texture coordinates. TexCoord is not a built-in variable (and with higher GLSL versions any builtin variables suitable for the job have been removed), so you need to fill that with value (and sense) in a vertex shader.

the glGetString(GL_VERSION) on the NVidia machine reads out OpenGL version 3.3.0. This is Ubuntu, so it might be possible that it differs with the windows specifications?

Do you have the NVidia propriatary drivers installed? And are they actually used? Check with glxinfo or glGetString(GL_RENDERER). OpenGL-3.3 is not too far from OpenGL-3.1 and in theory OpenGL major versions map to hardware capabilities.