深度测试问题

我有一个简单的OpenGL应用程序，我想绘制一个多维数据集，但深度缓冲区似乎以某种方式无法正常工作。我正在将SFML用于windowin系统，并将GLEW作为库。

主要内容如下：https : //pastebin.com/tq5t0TJN

...code...

网格类如下所示：https : //pastebin.com/YiWH8dWH

...code...

加载函数如下所示：https : //pastebin.com/vUNLn0gu-但它们似乎都能正常工作

...code...

现在我有了一个顶点着色器：https : //pastebin.com/EeP4RXHy

#version 330 core
layout (location = 0) in vec3 location_attrib;
layout (location = 1) in vec2 texcoord_attrib;
layout (location = 2) in vec3 normal_attrib;


out vec3 location;
out vec3 normal;


void main()
{
    normal = normal_attrib;
    gl_Position = vec4(location_attrib.x / 2, location_attrib.y  / 2, location_attrib.z  / 2, 1.0);
}

还有片段着色器：https : //pastebin.com/E9krMFZq

#version 330 core
out vec4 gl_FragColor;
//out float gl_FragDepth ;

in vec3 location;
in vec3 normal;

void main()
{
    vec3 normal_normalized = normalize(normal);
    vec3 light_dir = vec3(0, -1, 0);

    float light_amount = dot(normal_normalized, light_dir);

    vec3 color = vec3(1.0f, 0.5f, 0.2f);
    color = color * light_amount;
    color = clamp(color, vec3(0,0,0), vec3(1,1,1));
    color.r += 0.1;
    color.g += 0.1;
    color.b += 0.1;
    //gl_FragColor = vec4(color.r, color.g, color.b , 1.0);
    gl_FragDepth = location.z / 1000;
    gl_FragColor = vec4(vec3(gl_FragCoord.z), 1.0);
}

但是以这种方式获得的图像如下所示：

Can anybody tell what is the issue?

I tried to figure out what is wrong with the depth test, tried different combinations, but it all seems to not work.