// vert
#version 330

layout(location = 0) in vec3 in_VertCoord;
uniform mat4 MVP;

void main(){
    gl_Position = MVP * vec4(in_VertCoord, 1.0f);
}

//frag
#version 330

void main(){
    float val = gl_FragCoord.z * gl_FragCoord.w;
    gl_FragColor = vec4(val, val, val, 1.0f);
}