Dithered Opacity Shader For Godot 3.1

// My custom shader for implementing dithered alpha
shader_type spatial;
render_mode blend_mix,depth_draw_opaque,cull_disabled,diffuse_burley,specular_schlick_ggx;

// Texture maps
uniform sampler2D texture_albedo : hint_albedo;
uniform sampler2D texture_masks : hint_white;
uniform sampler2D texture_normal : hint_normal;

// Parameters
uniform vec4 albedo : hint_color;
uniform float specular = 0.5;
uniform float metallic = 0.0;
uniform float roughness : hint_range(0,1) = 0.5;
uniform float normal_strength : hint_range(0,2) = 1.0;
uniform float alpha_clip: hint_range(0,1) = 0.0;

void fragment() {
    vec4 albedo_tex = texture(texture_albedo, UV);
    vec4 masks_tex = texture(texture_masks, UV);
    float alpha = albedo_tex.a;

    ALBEDO = albedo.rgb * albedo_tex.rgb;
    METALLIC = metallic * masks_tex.r;
    ROUGHNESS = roughness * masks_tex.g;
    NORMALMAP = texture(texture_normal, UV).rgb;
    NORMALMAP_DEPTH = normal_strength;

    // Fancy dithered alpha stuff
    float opacity = albedo_tex.a;
    int x = int(FRAGCOORD.x) % 4;
    int y = int(FRAGCOORD.y) % 4;
    int index = x + y * 4;
    float limit = 0.0;

    if (x < 8) {
        if (index == 0) limit = 0.0625;
        if (index == 1) limit = 0.5625;
        if (index == 2) limit = 0.1875;
        if (index == 3) limit = 0.6875;
        if (index == 4) limit = 0.8125;
        if (index == 5) limit = 0.3125;
        if (index == 6) limit = 0.9375;
        if (index == 7) limit = 0.4375;
        if (index == 8) limit = 0.25;
        if (index == 9) limit = 0.75;
        if (index == 10) limit = 0.125;
        if (index == 11) limit = 0.625;
        if (index == 12) limit = 1.0;
        if (index == 13) limit = 0.5;
        if (index == 14) limit = 0.875;
        if (index == 15) limit = 0.375;
    }
    // Is this pixel below the opacity limit? Skip drawing it
    if (opacity < limit || opacity < alpha_clip)
        discard;
}