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coonoor
Journeyman III

ATI Driver Bug when mat4's are compared in shaders (windows xp and linux - ubuntu 10.04)

Operations that invlove comparison of mat4 matrices fails. Comparing the same matrices element by element succeeds

Hi,

 

 I am experiencing the following failure with my ATI GPU Drivers. This could be a problem with the GL Shader Compiler  that is used by the ATI Drivers.

Configuration

OS - Microsoft Windows XP Professional with SP2

GPU - ATO Radeon HD 2600 Pro

Driver version - 10.4 (from ATI Website)

Shader Program

The following shader returns incorrect result.

const mat4 ones_mat = mat4(1.0, 1.0, 1.0, 1.0,
               1.0, 1.0, 1.0, 1.0,
               1.0, 1.0, 1.0, 1.0,
               1.0, 1.0, 1.0, 1.0);
const mat4 zeros_mat = mat4(0.0, 0.0, 0.0, 0.0,
                0.0, 0.0, 0.0, 0.0,
                0.0, 0.0, 0.0, 0.0,
                0.0, 0.0, 0.0, 0.0);

bool matrix_equal(const in mat4 value, const in mat4 reference);
bool elements_equal(const in mat4 par, const in float value);

void main()
{
        mat4 var;
        var = ones_mat;
        if( matrix_equal(var, ones_mat ) )
            gl_FragColor = vec4(0.4,0.4,0.8,1.0);
}

bool matrix_equal(const in mat4 value, const in mat4 reference)
{
     if(value == reference)
         return true;
     else
         return false;

}

In the above shader, gl_FragColor should always be set to  vec4(0.4,0.4,0.8,1.0) as the comparison operations should return true. The comparison opeartion fails and hence the shader returns the uninitialized value (black color).

Comparing the matrices element by element returns the correct result. The complete fragment shader has been attached.

We have verified the shader with other GPUs (NVIDIA) and they return the expected ouput.  The problem has also been found with the latest ATI Drivers for Linux.

Linux Configuration

ATI Proprietary Linux Driver - 8.723

GPU - ATI Radeon HD 2600 Pro

 

Please let me know if a formal bug report needs to be raised. I am unsure of the forum it needs to be raised and hence posting it here.

 

Regards

Karthik

const mat4 ones_mat = mat4(1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0); bool matrix_equal(const in mat4 value, const in mat4 reference); bool elements_equal(const in mat4 par, const in float value); void main() { mat4 var; var = ones_mat; if( matrix_equal(var, ones_mat ) ) // if( elements_equal(var, 1.0) ) gl_FragColor = vec4(0.4,0.4,0.8,1.0); } bool matrix_equal(const in mat4 value, const in mat4 reference) { if(value == reference) return true; else return false; } bool elements_equal(const in mat4 par, const in float value) { bool ret = true; if(par[0][0] != value) ret = false; if(par[0][1] != value) ret = false; if(par[0][2] != value) ret = false; if(par[0][3] != value) ret = false; if(par[1][0] != value) ret = false; if(par[1][1] != value) ret = false; if(par[1][2] != value) ret = false; if(par[1][3] != value) ret = false; if(par[2][0] != value) ret = false; if(par[2][1] != value) ret = false; if(par[2][2] != value) ret = false; if(par[2][3] != value) ret = false; if(par[3][0] != value) ret = false; if(par[3][1] != value) ret = false; if(par[3][2] != value) ret = false; if(par[3][3] != value) ret = false; return ret; }

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13 Replies
coonoor
Journeyman III

ATI Driver Bug when mat4's are compared in shaders (windows xp and linux - ubuntu 10.04)

To add, this is a problem with mat2 and mat3 types as well. For example the following fragment shader program returns  incorrect output.

varying vec4 color;

const int ar_size = 2;

void main (void)
{
    const mat2 val1 = mat2(2.0, 2.0, 2.0, 2.0);
    const mat2 val2 = mat2(4.0, 4.0, 4.0, 4.0);
    mat2 array[ar_size];
    float gray;

    array[0] = val1;
    array[1] = val2;

    if((array[0] == val1) && (array[1] == val2))
        gray = 1.0;
    else
        gray = 0.0;

    gl_FragColor = vec4(gray, gray, gray, 1.0);
}

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coonoor
Journeyman III

ATI Driver Bug when mat4's are compared in shaders (windows xp and linux - ubuntu 10.04)

Some more bugs with the ATI Shader Compiler I guess. The following shader gives incorrect output.

 

void main (void){
      struct nest2
    {
       float f1;
    };

    struct nest1
    {
       ivec3 vc3;
       nest2 vnest2;
    };

    struct test_t
    {
           nest1 vnested;
    };
   

    test_t a = test_t(  nest1( ivec3(73, 74, 75), nest2(144.0) ) );

    float gray;
    if( (a.vnested.vc3[0] == 73) && (a.vnested.vnest2.f1 == 144.0)  )
    // if( (a.vnested.vc3[0] == 73)  )
        gray=0.4;
    else
            gray=0.0;
    gl_FragColor = vec4(gray, gray, gray, 1.0);
}

The variable gray should be set to 0.4. It is set to 0.0. We have checked with NVIDIA GPUs and this returns the expected result.

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coonoor
Journeyman III

ATI Driver Bug when mat4's are compared in shaders (windows xp and linux - ubuntu 10.04)

Continue statements dont work in some shaders;

Looks like the Shader Compiler has some more issues. In the following shader, the continue statement has no effect. When the continue statement is commented, the program runs fine. With the continue, it gives a wrong result.


void main (void)
{
    int cnt1 = 0, cnt2 = 0;
    int sum1 = 0, sum2 = 0;

        for(int i=0;i<4;i++)
    {
          cnt1++;
        cnt2 = 0;
        for(int j=0;j<4;j++)
        {
            cnt2++;
            if(cnt2 == 2){
                               cnt2 = cnt2;
                   continue;
                        }
            else
                sum2 += cnt2;
           
        }
       

          if(cnt1 == 2)
                {
                        cnt1 = cnt1;
                    continue;
                }
          else
                sum1 += cnt1;
   
    }
    float gray;
    if( (sum2 == 32) )
        gray=0.4;
    else
            gray=0.0;
    gl_FragColor = vec4(gray, gray, gray, 1.0);
}

We have used the same shader with NVIDIA GPu and it gives the expected output.

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frali
Staff
Staff

ATI Driver Bug when mat4's are compared in shaders (windows xp and linux - ubuntu 10.04)

Thanks for your feedback. Most of the bugs could be reproduced except the second one - matrix2 comparison. We will fix them as soon as possible.

Thanks
Frank

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coonoor
Journeyman III

ATI Driver Bug when mat4's are compared in shaders (windows xp and linux - ubuntu 10.04)

Thanks for your reply. With the matrix 2 comparison I am also not able to reproduce them. Will investigate further and let you know.

Also, theres one more issue I found with the drivers

When glBindAttribLocation is used with an invalid location (-1), then the error to be returned is GL_INVALID_VALUE. ATI Drivers accept what we give and return GL_NO_ERROR.

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coonoor
Journeyman III

Several ATI Driver Bugs (windows xp and linux - ubuntu 10.04)

The attached code returns GL_INVALID_OPERATION when Texture Image is attached to a framebuffer object. When a renderbuffer object is attached to a framebuffer object no error is returned.

In other words, the first call to glGetFramebufferAttachmentParameteriv fails but the second call succeeds.

Given that this extension is supported by the ATI Drivers, this is incorrect bahavior. Please let me know if you need more information.

GLuint tex; GLuint fb, rb; GLint buf[10]; GLenum error = GL_NO_ERROR; glGenTextures(1, &tex); glBindTexture(GL_TEXTURE_2D, tex); glGenFramebuffers(1, &fb); glBindFramebuffer(GL_FRAMEBUFFER, fb); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex, 0); glGetFramebufferAttachmentParameteriv(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE, buf); error = glGetError(); glGenRenderbuffers(1, &rb); glBindRenderbuffer(GL_RENDERBUFFER, rb); glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, rb); glGetFramebufferAttachmentParameteriv(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE, buf); error = glGetError();

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frali
Staff
Staff

ATI Driver Bug when mat4's are compared in shaders (windows xp and linux - ubuntu 10.04)

The four shader related problems have been all fixed. I can't find the problems in the latest driver. You'd better wait for about two or three months to have a try.

We will take a look at the other problems. Thanks again for your great feedback.

Frank

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lindsey
Journeyman III

ATI Driver Bug when mat4's are compared in shaders (windows xp and linux - ubuntu 10.04)

Thanks for your reply.             http://www.highnfljerseys.com

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coonoor
Journeyman III

ATI Driver Bug when mat4's are compared in shaders (windows xp and linux - ubuntu 10.04)

Hi,

 

 I have now downloaded the latest driver from the website and I am happy to say that the previous issues that I reported have been fixed. But some new bugs are showing up (as is with the bug fixing process ). The attached shader doesn't compile on ATI. It does fine on NVIDIA.

void main() { const struct struct1 { int i; vec4 v4; } struct1_var = struct1(8, vec4(9, 10, 11,12)); struct struct2 { int i; }; struct struct3 { struct1 s1; struct2 s2; } struct3_var = struct3(struct1_var, struct2(6)) ; const int i1 = struct3_var.s1.i * struct3_var.s2.i; const vec4 field4 = struct3_var.s1.v4 ; // 49, 64, 81, 100 gl_Position = field4; }

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