Linking errors with geometry- / tesselation-shader

OpenGL
1

Hi there!

i need help with geometry- / tesselation-shader. I have an application where i already use vertex- and fragment-shader, which works fine. No i’m trying to implement geometry- and tesselation-shaders for a while without success. Even the simpelest example-code will result in (glsl-)linking errors. This one for example:

Vertex shader:

void main() {        gl_Position = ftransform();    }

Geometry shader:

layout(points) in;
layout(line_strip, max_vertices = 2) out;

void main() {
    gl_Position = gl_in[0].gl_Position + vec4(-0.1, 0.0, 0.0, 0.0);
    EmitVertex();

    gl_Position = gl_in[0].gl_Position + vec4(0.1, 0.0, 0.0, 0.0);
    EmitVertex();

    EndPrimitive();
}

Fragment shader:

out vec4 outColor;

void main() {        outColor = vec4(1.0, 0.0, 0.0, 1.0);    }

Systeminfo:
System: Windows 10 on thinkpad X230
Renderer: Intel(R) HD Graphics 4000
GL-Version: 4.0.0 - Build 10.18.10.4358
SL-Version: 4.00 - Build 10.18.10.4358

Since i don’t know if the problem is the shader- or the c-code, here is the C++ code (note: the program can be edited while running. As long there are errors, the previous program stays active):


    // create new shader while current are still working
    vShNewHandle            = glCreateShader  (GL_VERTEX_SHADER); 
    tcShNewHandle           = glCreateShader  (GL_TESS_CONTROL_SHADER); 
    teShNewHandle           = glCreateShader  (GL_TESS_EVALUATION_SHADER);
    gShNewHandle            = glCreateShader  (GL_GEOMETRY_SHADER);   
    fShNewHandle            = glCreateShader  (GL_FRAGMENT_SHADER);   
    prgNewHandle            = glCreateProgram (); 

    // regular expression for testing if shader-code contains a main-function (if not, the specific shader is not compiled and linked) 
    regEx hasCode ("[\
\\r][\	 ]*void\\s*main\\s*\\(");
    if (hasCode.errmsg()) exit(0);
    
    // compile vertex-shader & attach it to new program
    success                 = GL_FALSE;                                     errHandle           = vShNewHandle;   
    glShaderSource          (vShNewHandle, 1, &vs, NULL);                   glCompileShader     (vShNewHandle); 
    glGetShaderiv           (vShNewHandle,  GL_COMPILE_STATUS, &success);   if (success != GL_TRUE) goto ex;
    glAttachShader          (prgNewHandle, vShNewHandle); 
 
    // if exist compile tesselation-shader & attach them to new program
    if (hasCode.Matches(shdShader->tcShSrc) && hasCode.Matches(shdShader->teShSrc)) {
        success             = GL_FALSE;                                     errHandle           = tcShNewHandle;   
        glShaderSource      (tcShNewHandle, 1, &tcs, NULL);                 glCompileShader     (tcShNewHandle);
        glGetShaderiv       (tcShNewHandle, GL_COMPILE_STATUS, &success);   if (success != GL_TRUE) goto ex;
        glAttachShader      (prgNewHandle, tcShNewHandle);

        success             = GL_FALSE;                                     errHandle           = teShNewHandle;   
        glShaderSource      (teShNewHandle, 1, &tes, NULL);                 glCompileShader     (teShNewHandle);
        glGetShaderiv       (teShNewHandle, GL_COMPILE_STATUS, &success);   if (success != GL_TRUE) goto ex;
        glAttachShader      (prgNewHandle, teShNewHandle); 
    }  
          
    // if exist compile geometry-shader & attach them to new program
    if (hasCode.Matches(shdShader->gShSrc)) {       
        success             = GL_FALSE;                                     errHandle           = gShNewHandle;   
        glShaderSource      (gShNewHandle, 1, &gs, NULL);                   glCompileShader     (gShNewHandle);
        glGetShaderiv       (gShNewHandle, GL_COMPILE_STATUS, &success);    if (success != GL_TRUE) goto ex;
        glAttachShader      (prgNewHandle, gShNewHandle);
    }        

    // compile fragment-shader & attach it to new program
    success                 = GL_FALSE;                                     errHandle           = fShNewHandle;   
    glShaderSource          (fShNewHandle, 1, &fs, NULL);                   glCompileShader     (fShNewHandle);
    glGetShaderiv           (fShNewHandle,  GL_COMPILE_STATUS, &success);   if (success != GL_TRUE) goto ex;
    glAttachShader          (prgNewHandle, fShNewHandle);

    // link new program - THIS IS, WHERE THE ERROR APPEARS
    success                 = GL_FALSE;                                     errHandle           = prgNewHandle;   
    glUseProgram            (prgNewHandle);                                 glLinkProgram       (prgNewHandle);  
    glGetProgramiv          (prgNewHandle, GL_LINK_STATUS,   &success);     if (success != GL_TRUE) goto ex;
    
    // if successful so far, swap active handles with used handels
    GLuint tmpHandle;
    tmpHandle               = vShHandle;        vShHandle  = vShNewHandle;  vShNewHandle  = tmpHandle;
    tmpHandle               = tcShHandle;       tcShHandle = tcShNewHandle; tcShNewHandle = tmpHandle;
    tmpHandle               = teShHandle;       teShHandle = teShNewHandle; teShNewHandle = tmpHandle;
    tmpHandle               = gShHandle;        gShHandle  = gShNewHandle;  gShNewHandle  = tmpHandle;
    tmpHandle               = fShHandle;        fShHandle  = fShNewHandle;  fShNewHandle  = tmpHandle;
    tmpHandle               = prgHandle;        prgHandle  = prgNewHandle;  prgNewHandle  = tmpHandle;

    canLink                 = true; 

ex:
    // dispay error-message if there is one
    OutStatus               (); 

    // delete handles, which are the new handels if the progam has errors or the old progam if the new program is okay.
    glUseProgram            (0);        
    glDeleteProgram         (prgNewHandle);
    glDeleteShader          (vShNewHandle); 
    glDeleteShader          (tcShNewHandle); 
    glDeleteShader          (teShNewHandle); 
    glDeleteShader          (gShNewHandle); 
    glDeleteShader          (fShNewHandle);

As long as there is no geometry- or tesselation-shader is used, everything works fine but if i try to use them the program is not linked anymore.
Is there anyone who has an idea what is wrong??

Thank you for reading…

Kind regards,
Frank

2

Okay, now i have a working geometry-shader, but i don’t really know, why it works now. The only point i’m sure is: the problem was not the C-Code.

But still i have Problems with tesselation-shaders. I’ll start a new thread with this…

For completeness here is the working geometry-shader:

layout(triangles) in;
layout(line_strip, max_vertices = 3) out;

vec4 normalVec(vec4 p, vec4 vX, vec4 vY) {
    vX  = vX - p;   vY  = vY - p;
    p.x = (vX.y * vY.z) - (vX.z * vY.y);
    p.y = (vX.z * vY.x) - (vX.x * vY.z);
    p.z = (vX.x * vY.y) - (vX.y * vY.x);
    p.w = (vX.w * vY.w) - (vX.w * vY.w);
    return p;
}

void main()
{
    vec4 test = normalVec(gl_in[0].gl_Position,gl_in[1].gl_Position,gl_in[2].gl_Position);
    gl_Position = gl_in[0].gl_Position;// + gl_in[1].gl_Position;//vec4(-0.1, 0.0, 0.0, 0.0);
    EmitVertex();

    gl_Position = gl_in[0].gl_Position+test*16 ;//gl_in[1].gl_Position;// * gl_in[0].gl_Position;// vec4(0.1, 0.1, 0.0, 0.0);
    EmitVertex();

    gl_Position = gl_in[2].gl_Position;// + gl_in[0].gl_Position.x;// vec4(0.1, 0.1, 0.0, 0.0);
    EmitVertex();

    EndPrimitive();
}

Regards,
Frank

3

What errors, exactly? Call glGetProgramInfoLog() to obtain any errors or other messages related to linking.

4

I already use glGetShaderInfoLog but unfortunately linking-errors are not specified in the log-text.

But anyway, i’m a little further on in between. I have a working example with geometry-shader. But i’m still missing a working tesselation-shader (see my new post here).

Thanks anyway for replying…

PS. is there any possibility to mark the thread as “solved”??

5

glGetShaderInfoLog(…) != glGetProgramInfoLog(…)

the latter should give you infos about linking errors

6

UUps…

You’re right. Now i get correct linking-error-messages - thanks a lot :wink:

Regards,
Frank

7

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