OpenGL glGetUniformLocation for Sampler2D在树莓派上返回-1，但在Windows

我正在制作一个跨平台的OpenGL程序。然而，我遇到了一个问题，其中glGetUniformLocation，它应该返回我的着色器程序中统一变量的位置，返回-1，它只发生在Linux上(树莓派发行版，在树莓派上运行)，在Windows上相同的代码工作完美!下面是我的代码:

Load Shader程序函数:

int shader, status;
programID = glCreateProgram();
// Load vertex shader
shader = LoadShaderFromString(GL_VERTEX_SHADER, Tools::GetFileAsString("VertexShader.glsl"), "Unable to compile vertex shader.n");
glAttachShader(programID, shader);
// Load pixel shader
shader = LoadShaderFromString(GL_FRAGMENT_SHADER, Tools::GetFileAsString("FilterPixelShader.glsl"), "Unable to compile pixel shader.n");
glAttachShader(programID, shader);
// Link the program
glLinkProgram(programID);
glGetProgramiv(programID, GL_LINK_STATUS, &status);
if (status == 0)
{
    Log("Unable to link filter shader program.n");
    PrintProgramLog(programID);
    Fail();     // Quits program
}   
// returns -1 here!
frameTextureLocation = glGetUniformLocation(programID, "FrameTextureUnit");
if (frameTextureLocation == -1)
{
    int errorCode = glGetError();
    Log(string("Error retrieving variable frameTextureLocation from shader program: "));
    Log((const char*)glewGetErrorString(errorCode))
    Log("!n");
    Fail();
}

LoadShaderFromString:

int Shader::LoadShaderFromString(int type, const string& shaderSource, const string& errorMessage)
{
    int shader, status;
    const char* programSource;
    shader = glCreateShader(type);
    programSource = shaderSource.c_str();
    glShaderSource(shader, 1, &programSource, nullptr);
    glCompileShader(shader);
    glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
    if (status == 0)
    {
        Log(errorMessage);
        PrintShaderLog(shader);
        Fail();
    }
    return shader;
}

最后，着色器本身:

uniform sampler2D FrameTextureUnit; 
uniform sampler2D BackgroundTextureUnit;
#if __VERSION__ >= 130 
    // Texture coordinate 
    in vec2 texCoord; 
    // Final color 
    out vec4 gl_FragColor; 
#else
    // Texture coordinate 
    varying vec2 texCoord; 
#endif
uniform float Tolerance;                    // Tolerance for color difference
uniform vec4 FilterColor;                   // Color of the filter
void main()
{
    vec4 pixel = texture2D(FrameTextureUnit, texCoord);
    vec4 background = texture2D(BackgroundTextureUnit, texCoord);
    float difference = abs(background.x - pixel.x)
                   + abs(background.y - pixel.y)
                   + abs(background.z - pixel.z);
    if (difference > Tolerance)
    {
        gl_FragColor = FilterColor;
    }
    else
    {
        // Y = 0.2126 R + 0.7152 G + 0.0722 B 
        float gray = pixel.x * 0.2126 + pixel.y * 0.7152 + pixel.z * 0.0722;
        gl_FragColor = vec4(gray, gray, gray, 1);
    }
}

有人知道为什么会发生这种情况吗?值得添加的是错误处理代码:

    int errorCode = glGetError();
    Log(string("Error retrieving variable frameTextureLocation from shader program: "));
    Log((const char*)glewGetErrorString(errorCode));

打印"从shader程序中检索变量frameTextureLocation出错:No Error ".