GLSL着色器在Intel集成GPU上运行完美，但在NVIDIA上却没有

Question

I'm using Geometry Shaders for Geometry Amplification. The code runs perfectly with Intel graphics both in Windows and OS X.

I change the configs to use the dedicated NVIDIA GPU from my windows machine aaaaaaaaaaand... nothing.

This code:

    void testError(std::string src) {
        GLenum err = glGetError();
       if (err != GL_NO_ERROR){
           printf("(%s) Error: %s %d\n", src.c_str(), gluErrorString(err), err);
        }
    }

    ...

    printf("glIsProgram: %s\n", glIsProgram(shaderProgram)?"True":"false");
    glUseProgram(shaderProgram);
    testError("GOGO 111");
    GLint isLinked = 0;
    glGetProgramiv(shaderProgram, GL_LINK_STATUS, (int *)&isLinked);
    if (isLinked == GL_FALSE)
    {
        GLint maxLength = 0;
        glGetProgramiv(shaderProgram, GL_INFO_LOG_LENGTH, &maxLength);

        //The maxLength includes the NULL character
        std::vector<GLchar> infoLog(maxLength);
        glGetProgramInfoLog(shaderProgram, maxLength, &maxLength, &infoLog[0]);
        printf("Program Not Linked %d:\n %s\n", maxLength, infoLog);
        //We don't need the program anymore.
        glDeleteProgram(shaderProgram);

        //Use the infoLog as you see fit.

        //In this simple program, we'll just leave
        return 0;
    }

Outputs:

    glIsProgram: True
    (GOGO 111) Error: invalid operation 1282
    Program Not Linked 116:
     ­Ð

Also the Log have a strange behaviour since it is not printing nothing but the length would be 116.

Thank you.

EDIT This:

char * infoLog;
glGetProgramiv(shaderProgram, GL_INFO_LOG_LENGTH, &maxLength);

Printed out the result.

Program Not Linked 116:
 Geometry info
 -------------
 (0) : error C6033: Hardware limitation reached, can only emit 128 vertices of this size

Which comes from:

const GLchar* geometryShaderSrc = GLSL(
    layout(points) in;
    layout(triangle_strip, max_vertices = 256) out;
...

It's just weird that the Intel integrated GPUS have less hardware (memory?) imitations that an NVIDIA GPU. Any solution to go around this without decreasing the vertices?

Answer 1

It looks like you're exceeding the GEOMETRY_TOTAL_OUTPUT_COMPONENTS limit.

In the OpenGL 4.4 Spec - Section 11.3.4.5 - page 388

The product of the total number of vertices and the sum of all components of all active output variables may not exceed the value of MAX_GEOMETRY_TOTAL_OUTPUT_COMPONENTS . LinkProgram will fail if it determines that the total component limit would be violated.

ie max_vertices cannot exceed MAX_GEOMETRY_TOTAL_OUTPUT_COMPONENTS / number_of_components

The minimum requirements are detailed in Table 23.60 - page 585

GEOMETRY_TOTAL_OUTPUT_COMPONENTS 1024

It seems like you have 8 components, so can only have 128 vertices. You must either decrease the number of components, or decrease the number of vertices.

Check the value of GEOMETRY_TOTAL_OUTPUT_COMPONENTS on each device to make sure.