#version 300 es
precision highp float;
in vec4 vColor;
uniform highp sampler2D u_sceneDepth;
uniform vec2 u_invViewport;   // 1 / current framebuffer size
out vec4 fragColor;
void main() {
    // manual depth test against the scene pass (drawn post-PP, so no hardware depth to test against);
    // primitive depths carry the scene pass polygon offset, so coplanar wireframes win the compare.
    // sampled by normalized screen position — stays correct if the scene renders at another resolution
    float sceneDepth = texture(u_sceneDepth, gl_FragCoord.xy * u_invViewport).r;
    if (gl_FragCoord.z > sceneDepth)
        discard;
    fragColor = vColor;
}