Halftone directional fading transition

Important: part of this code has been written by Zacksly for another Godot shader published under MIT licence. He has the merit for the halftone processing, I’ve just copied it and edited as canvas item (I’ve looked for other sources, but with no luck). I’m putting here the link for the original shader on Itch.io, both due to the only restriction of MIT licence and because looking original shader is really worth it:
https://zacksly.itch.io/half-tone-comic-shader-for-godot
I’m also leaving the comments of the original code, so you can see what I’ve effectively edited.

Parameters:

• Transparent Dot: if it’s true, the dots will be in the transparent side (see the screenshots 2 & 3).
• Aspect Ratio: referred to the dots.
• Dots: the number of dots in each row, columns are affected due to aspect ratio.
• Min and Max: referred to the density of dots.
• Height: the height of the curtain. If it’s -1.0 the entire canvas is transparent, if it’s higher, a part of the canvas is filled by the halftone effect, if it’s 1.0 the entire canvas is filled. Change this value to make the fade transition:
  canvas_item.material.get("shader_param/height", height)

Behaviour:

• This shader behaves like a drama curtain: a black filter fills the canvas item of a texture from downside, leaving the remaining part transparent. To use it, you have to add it directly to a canvas item as shader material.
• If you want to make the transition from another direction, for example from upside, you have to rotate the canvas item.
• It’s supposed to work in Control rects, but sprites and other node2D’s should work as well.
• If you use it on a Color rect, the shader ignores the Color property of the node, use Modulate instead.
• The shader works in any version with any backend (or, if there are sintax differences, I’ve not found ’em yet)

Shader code

// Original : Shader By Zacksly - https://zacksly.itch.io/
shader_type canvas_item;
//uniform bool UseColor; //removed because unnecessary in this case
uniform bool TransparentDot;
uniform float AspectRatio = 1.5;
uniform float Dots = 10.0;
uniform float _min;
uniform float _max = 1.0;
//uniform bool UseReshade; //removed because unnecessary in this case

uniform float height = 0.0;

void fragment() {

	vec3 uv_grid = fract(vec3(UV, 0.0) * vec3(AspectRatio * Dots, Dots, 0.0)); // replaced SCREEN_UV with UV

	float grid = distance(uv_grid, vec3(0.5, 0.5, 0.5));
	/*
	vec3 raw_cam_image;
	{
		//vec4 _tex_read = textureLod(SCREEN_TEXTURE, SCREEN_UV, 0.0);
		raw_cam_image = _tex_read.rgb;
	}
	*/// removed because in this case ScreenTexture isn't used
	vec3 raw_cam_image = vec3(1,1,1) * (UV.y + height);
	vec3 grayscale;
	{
		float max1 = max(raw_cam_image.r, raw_cam_image.g);
		float max2 = max(max1, raw_cam_image.b);
		float max3 = max(max1, max2);
		grayscale = vec3(max3, max3, max3);
	}

	vec3 clamped = clamp(grayscale, vec3(_min), vec3(_max));

	bool black_dot_grid = grid > dot(vec3(1.0, 1.0, 1.0) - clamped, vec3(0.333333, 0.333333, 0.333333));
	bool white_dot_grid = grid < dot(clamped, vec3(0.333333, 0.333333, 0.333333));

	vec4 texture_uv = texture(TEXTURE,UV);
	//vec3 grid_result = BlackDot ? vec3(black_dot_grid ? 1.0 : 0.0) : vec3(white_dot_grid ? 1.0 : 0.0);	//vec4(texture_uv.r,texture_uv.g,texture_uv.b,1.0)
	vec4 grid_result = TransparentDot? (black_dot_grid? texture_uv : vec4(0.0)): (white_dot_grid? texture_uv : vec4(0.0));
	/*
	vec3 saturated_image = vec3(0.0, 0.0, 0.0);
	{
		if (abs(raw_cam_image.r - raw_cam_image.g) +
			abs(raw_cam_image.g - raw_cam_image.b) +
			abs(raw_cam_image.b - raw_cam_image.r) > .1 )
		{
			raw_cam_image.rgb = mix(vec3(0.0), raw_cam_image.rgb, 2); //Brightness
			raw_cam_image.rgb = mix(vec3(0.5), raw_cam_image.rgb, 1); // Contrast
			raw_cam_image.rgb = mix(vec3(dot(vec3(1.0), raw_cam_image.rgb)*0.33333), raw_cam_image.rgb, 2); //Saturation
		} else {
			raw_cam_image = vec3(1.0,1.0,1.0);
		}
		saturated_image.rgb = raw_cam_image;
	}*/// removed because UseReshade hasn't been used

	//vec3 screen_image = UseReshade ? saturated_image : raw_cam_image;

	//vec3 final_image = UseColor ? grid_result * screen_image : grid_result;

	COLOR.rgb = grid_result.rgb;
	
	COLOR.a = grid_result.a;
}

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